Placental barrier in anesthetic terms. Pharmacokinetics and pharmacodynamics of drugs used in obstetric anesthesiology. Placental barrier
1. The structure of the placenta. The surface of the placenta. Microscopic structure of mature placental villi.
2. Uterine - placental circulation.
3. Features of blood circulation in the mother - placenta - fetus system.
4. The main functions of the placenta.
5. Respiratory function of the placenta. Trophic function of the placenta.
6. Endocrine function of the placenta. Placental lactogen. Chorionic gonodotropin (HCG, HCG). Prolactin. Progesterone.
7. Immune system of the placenta. Placenta barrier function.
8. Amniotic fluid. Amniotic fluid volume. Amniotic fluid. Functions of amniotic fluid.
9. Umbilical cord and afterbirth. Umbilical cord (umbilical cord). Variants of attachment of the umbilical cord to the placenta. The dimensions of the umbilical cord.
Placental immune system. Placenta barrier function.
Placental immune system.
The placenta is a kind immune barrier, separating two genetically alien organisms (mother and fetus), therefore, during a physiologically proceeding pregnancy, an immune conflict between the organisms of the mother and the fetus does not arise. The absence of an immunological conflict between the organisms of the mother and the fetus is due to the following mechanisms:
The absence or immaturity of the antigenic properties of the fetus;
- the presence of an immune barrier between the mother and the fetus (placenta);
- immunological characteristics of the mother's body during pregnancy.
Placenta barrier function.
Concept " placental barrier"includes the following histological formations: syncytiotrophoblast, cytotrophoblast, layer of mesenchymal cells (villous stroma) and endothelium of the fetal capillary. The placental barrier can to some extent be likened to the blood-brain barrier, which regulates the penetration of various substances from the blood into the cerebrospinal fluid. from the blood-brain barrier, the selective permeability of which is characterized by the transition of various substances in only one direction (blood - cerebrospinal fluid), placental barrier regulates the transfer of substances in the opposite direction, i.e. from fetus to mother. The transplacental transition of substances that are constantly in the mother's blood and that have fallen into it by accident is subject to different laws. The transition from mother to fetus of chemical compounds that are constantly present in the mother's blood (oxygen, proteins, lipids, carbohydrates, vitamins, trace elements, etc.) is regulated by fairly precise mechanisms, as a result of which some substances are contained in the mother's blood in higher concentrations than in the blood of the fetus, and vice versa. In relation to substances that accidentally entered the maternal organism (agents of chemical production, drugs, etc.), the barrier functions of the placenta are expressed to a much lesser extent.
Placental permeability is variable... In physiological pregnancy, the permeability of the placental barrier progressively increases up to the 32-35th week of pregnancy, and then slightly decreases. This is due to the structural features of the placenta at different stages of pregnancy, as well as the needs of the fetus in certain chemical compounds.
Limited barrier functions the placenta in relation to chemicals that accidentally entered the mother's body are manifested in the fact that toxic products of chemical production, most drugs, nicotine, alcohol, pesticides, infectious agents, etc. pass through the placenta relatively easily. This creates a real danger for the adverse effects of these agents on the embryo and fetus.
Barrier function of the placenta they are most fully manifested only under physiological conditions, i.e. with uncomplicated pregnancy. Under the influence of pathogenic factors (microorganisms and their toxins, sensitization of the mother's body, the effects of alcohol, nicotine, drugs), the barrier function of the placenta is disrupted, and it becomes permeable even for substances that, under normal physiological conditions, pass through it in limited quantities.
Transport of drugs across the placenta is a complex and poorly researched problem. The placental barrier is functionally similar to the hematologic barrier. However, the selectivity of the blood-cerebrospinal fluid barrier is carried out in the direction of blood-cerebrospinal fluid, and the placental barrier regulates the transfer of substances from the mother's blood to the fetus and in the opposite direction.
The placental barrier differs significantly from other histo-hematological barriers in that it is involved in the exchange of substances between two organisms that have significant independence. Therefore, the placental barrier is not a typical histohematogenous barrier, but it plays an important role in protecting the developing fetus.
The morphological structures of the placental barrier are the epithelial cover of the chorionic villi and the endothelium of the capillaries located in them. Syncytiotrophoblast and cytotrophoblast have high absorption and enzymatic activity. Such properties of these layers of the placenta largely determine the possibility of penetration of substances. An essential role in this process is played by the activity of nuclei, mitochondria, endoplasmic reticulum and other ultrastructures of placental cells. The protective function of the placenta is limited to certain limits. So, the transition from mother to fetus of proteins, fats, carbohydrates, vitamins, electrolytes, which are constantly contained in the mother's blood, is regulated by mechanisms that have arisen in the placenta in the process of phylo- and ontogenesis.
Studies of transplacental drug transport were carried out mainly on drugs used in obstetrics. There is evidence from experiments with chemicals illustrating the rapid transition from mother to fetus of ethyl alcohol, chloral hydrate, general anesthetic gases, barbiturates, sulfamides and antibiotics. There is also indirect evidence of the transfer of morphine, heroin and other drugs through the placenta, since withdrawal symptoms are found in newborn children from mothers of drug addicts.
More than 10,000 children with limb deformities (phocomelia) and other pathological signs, born to women who took thalidomide during pregnancy, are another sad evidence of transplacental drug transfer.
The transfer of drugs through the placental barrier occurs through all the mechanisms discussed above, of which passive diffusion is of the greatest importance. Non-dissociated and non-ionized substances pass through the placenta quickly, and ionized ones - with difficulty. Facilitated diffusion is in principle possible, but has not been proven for specific drugs.
The transfer rate also depends on the size of the molecules, since the placenta is impermeable to substances with a molecular weight of more than 1000. This is due to the fact that the pore diameter in the placenta does not exceed 10 nm and therefore only low molecular weight substances penetrate through them. Such an obstacle is especially important with the short-term use of certain substances, for example, blockers of neuromuscular synapses. However, with long-term use, many drugs can gradually penetrate the fetus.
Finally, proteins such as gamma globulin can penetrate through pinocytosis.
Cervical ammonium bases, as well as muscle relaxants (decametonite, succinylcholine) penetrate the placenta with difficulty, due to their high degree of ionization and low lipid solubility.
From the fetus, drugs are excreted by reverse diffusion through the placenta and renal excretion into the amniotic fluid.
Therefore, the content of a foreign substance in the body of the fetus differs little from that of the mother. Considering the fact that the binding of drugs to blood proteins in the fetus is limited, their concentration is 10-30% lower than in the mother's blood. However, lipophilic compounds (thiopental) accumulate in the liver and adipose tissue of the fetus.
Unlike other barrier functions, placental permeability varies widely during pregnancy, due to the increasing needs of the fetus. There is evidence of an increase in permeability towards the end of pregnancy. This is due to changes in the structure of the boundary membranes, including the disappearance of the cytotrophoblast and the gradual thinning of the synticyotrophoblast of the villi of the placenta. Placenta permeability in the second half of pregnancy does not increase to all substances introduced into the mother's body. So, the permeability of sodium bromide, thyroxine and oxacillin is higher not at the end, but at the beginning of pregnancy. Apparently, the uniform or limited supply of a number of chemicals to the fetus depends not only on the permeability of the placental barrier, but also on the degree of development of the most important fetal systems that regulate its needs and homeostasis processes.
The mature placenta contains a set of enzymes that catalyze drug metabolism (CYP) and transport proteins (OCTNl / 2, OCN3, OAT4, ENTl / 2, P-gp). Enzymes can be produced during pregnancy, therefore, the metabolic processes occurring in the placenta, as well as the duration of drug use, should be taken into account when deciding whether the fetus may be exposed to a substance circulating in the blood of a pregnant woman.
When discussing the role of histo-hematological barriers in the selective distribution of drugs in the body, it is necessary to note at least three more factors that influence this process. First, it depends on whether the drug is in free or protein-bound form in the blood. For the majority of histo-hematological barriers, the binding form of the substance is an obstacle to their entry into the corresponding organ or tissue. Thus, the content of sulfonamides in the cerebrospinal fluid correlates only with the part that is in the free state in the blood. A similar picture was observed for thiopental when studying its transport across the blood-ophthalmic barrier.
Secondly, some biologically active substances contained in blood and tissues or introduced from the outside (histamine, kinins, acetylcholine, hyaluronidase) in physiological concentrations reduce the protective functions of the histo-hematological barriers. The opposite effect is exerted by catecholamines, calcium salts, vitamin P.
Thirdly, in pathological conditions of the body, histo-hematic barriers are often rearranged, with an increase or decrease in their permeability. The inflammatory process in the membranes of the eye leads to a sharp weakening of the blood-ophthalmic barrier. When studying the entry of penicillin into the cerebrospinal fluid of rabbits in control and experiment (experimental meningitis), its content was 10-20 times higher in the latter case.
Consequently, it is difficult to imagine that even substances similar in structure along the distribution profile will behave in a similar way. This is due to the fact that this process depends on numerous factors: the chemical structure and physicochemical properties of drugs, their interaction with plasma proteins, metabolism, tropism to certain tissues, the state of histo-hematological barriers.
Today, many mothers know about pregnancy by far more than our parents knew. Therefore, many women during pregnancy are worried about their state of health, and they are very worried if the doctor talks about the state of such an important organ during pregnancy as the placenta. This organ performs the most important functions, and without it, it is impossible to carry a pregnancy in principle.
Deviations in the structure or functioning of the placenta can threaten complications for the mother or fetus, and certain measures must be taken in a timely manner to correct everything. But what can happen to the placenta, and how can it be dangerous? Let's figure it out together.
What is the placenta?
The term "placenta" itself comes from the Greek language and is translated by the simple word "cake". Indeed, in appearance, the placenta resembles a large and voluminous cake with a "tail" extending from it in the form of an umbilical cord. But this cake is extremely important for every woman carrying a baby, it is due to the existence of the placenta that it is possible to endure and normally give birth to a child.
According to the structure of the placenta, or, as it can be called in another way in the literature, "children's place", is a complex organ. The beginning of its formation occurs at the time of implantation of the embryo into the wall of the uterus (from the moment the embryo is attached to one of the walls of the uterus).
How does the placenta work?
The main part of the placenta are special villi that branch out in it and form from the beginning of pregnancy, resembling the branches of centuries-old trees. The baby's blood circulates inside the villi, and outside the villi are actively washed by the blood coming from the mother. That is, the placenta combines two circulatory systems at once - the maternal from the side of the uterus, and the fetal, from the side of the amniotic membranes and the baby. According to this, the sides of the placenta are also distinguished - smooth, covered with membranes, with a branching umbilical cord - from the fetus, and an uneven lobular - from the mother.
What is the placental barrier?
It is in the area of the villi that an active and constant exchange of substances takes place between the baby and his mother. Oxygen and all the necessary nutrients for growth and development are supplied from the mother's blood to the fetus, and the baby gives the mother metabolic products and carbon dioxide, which the mother removes from the body in two. And the most important thing is that the blood of the mother and the fetus does not mix in any part of the placenta. The two vascular systems - the fetus and the mother - are separated by a unique membrane that is capable of selectively passing some substances and retaining other, harmful substances. This membrane is called the placental barrier.
Gradually forming and developing with the fetus, the placenta begins to fully function by about twelve weeks of pregnancy. The placenta retains bacteria and viruses that penetrate into the maternal blood, special maternal antibodies that can be produced in the presence of Rh-conflict, but at the same time the placenta easily passes the nutrients and oxygen necessary for the child. The placental barrier has the property of special selectivity, different substances coming from different sides of the placental barrier penetrate the membrane to varying degrees. So, many minerals from the mother actively penetrate to the fetus, but practically do not penetrate from the fetus to the mother. And also, many toxic substances from the baby actively penetrate to the mother, and practically do not pass back from her.
Hormonal function of the placenta
In addition to the excretory function, the implementation of fetal respiration (since the placenta temporarily replaces the baby's lungs), and many other functions, the placenta has another function that is important for pregnancy as a whole - hormonal. The placenta, with the beginning of its full functioning, can produce up to 15 different hormones that perform various functions during the carrying of a baby. The very first of these are sexual functions, which help in maintaining and prolonging pregnancy. Therefore, gynecologists, with the threat of termination of pregnancy in an early period, always wait 12-14 weeks, helping in the early weeks of pregnancy with hormones from the outside (dyufaston or morning). Then the placenta begins to work actively and the threat disappears.
The functions of the placenta are so great that in the initial stages, the placenta grows and develops even faster than your baby grows. And this is not without reason, the fetus weighs about 5 grams by 12 weeks, and the placenta is up to 30 grams, by the end of pregnancy, at the time of delivery, the size of the placenta will be about 15-18 cm, and its thickness is up to 3 cm, with a weight of about 500 -600 grams.
Umbilical cord
From the side of the fetus, the placenta is connected to the baby with a special strong cord - the umbilical cord, inside which two arteries and one vein pass. The umbilical cord can attach to the placenta in several ways. The first and most common is central cord attachment, but lateral or marginal cord attachment may also occur. The function of the umbilical cord does not suffer from the method of attachment. A very rare option for attaching the umbilical cord may be attachment not to the placenta itself, but to its fetal membranes, and this type of attachment is called meningeal.
Placenta problems
Most often, the placenta and umbilical cord system works harmoniously and supplies the baby with oxygen and nutrition. But sometimes malfunctions can occur in the placenta due to the influence of various factors - external or internal. There are various kinds of developmental disorders or problems with the functioning of the placenta. Such changes in the placenta do not go unnoticed for the mother and the fetus, often problems with the placenta can have serious consequences. We will talk with you about the main abnormalities in the development and functioning of the placenta and how to identify and treat them.
Placental hypoplasia
A decrease in the size or thinning of the placenta in medical language is called "placental hypoplasia". Do not be afraid of this diagnosis, because it occurs quite often. The fetus is affected only by a significant decrease in the diameter and thickness of the placenta.
A significantly reduced placenta, a small child's place, is uncommon. Such a diagnosis is made if the decrease in size is significant compared to the lower limit of the norm for the size of the placenta at a given stage of pregnancy. The reasons for this type of pathology have not yet been clarified, but according to statistics, usually a small placenta is associated with the development of severe genetic abnormalities in the fetus.
I would like to immediately make a reservation that the diagnosis of "placental hypoplasia" is not made according to one ultrasound scan, it can only be made as a result of long-term monitoring of the pregnant woman. In addition, it is always worth remembering that there may be individual deviations in the size of the placenta from the standard, generally accepted normal values, which will not be considered a pathology for each particular pregnant woman in each of her pregnancies. So, for a small and slender woman, the placenta should be smaller in size than for a large and tall one. In addition, there is no one hundred percent evidence of the dependence of placental hypoplasia and the presence of genetic disorders in the fetus. But when diagnosed with placental hypoplasia, parents will be advised to undergo medical genetic counseling.
During pregnancy, a secondary decrease in the size of the placenta may occur, which may be associated with the impact of various adverse factors during the carrying of the baby. It can be chronic stress or starvation, alcohol or smoking, drug addiction. Also, the reasons for the underdevelopment of the placenta during pregnancy can be hypertension in the mother, a sharp exacerbation of chronic pathology, or the development of some acute infections during pregnancy. But in the first places with underdevelopment of the placenta is gestosis with the development of severe edema, high blood pressure and the appearance of protein in the urine.
Changes in the thickness of the placenta occur. Thinned placenta is considered, which has an insufficient mass at a size that is quite normal for its timing. Often, such thin placentas are found in congenital malformations of the fetus, and children are born with manifestations, which gives serious problems to the health of the newborn. But unlike the primary hypoplastic placenta, such children are not associated with the risk of developing dementia.
Sometimes a filmy placenta is formed - it is very wide and very thin, up to 40 cm in diameter, almost twice as large as normal. Usually, the cause of the development of such a problem is a chronic inflammatory process in the endometrium, which leads to dystrophy (depletion) of the endometrium.
Placental hyperplasia
In contrast, there is a variant of a very large, giant placenta, which usually occurs in cases of severe diabetes during pregnancy. Enlargement (hyperplasia) of the placenta is also found in diseases of pregnant women such as toxoplasmosis or syphilis, but this happens infrequently. An increase in the size of the placenta may be the result of kidney pathology in the unborn baby, if present, when the fetal red blood cells with Rh protein begin to attack the mother's antibodies. The placenta can increase significantly in the case of thrombosis of its vessels, if one of the vessels is blocked, as well as in case of pathological growth of small vessels inside the villi.
An increase in the thickness of the placenta more than normal may be associated with its premature aging. Thickening of the placenta is also caused by such pathologies as Rh-conflict, dropsy of the fetus, diabetes mellitus of a pregnant woman, gestosis, viral or infectious diseases transferred during pregnancy, placental abruption. A thickening of the placenta is normal in multiple pregnancies.
In the first and second trimesters, an increase in the placenta usually indicates a past viral disease (or latent carriage of the virus). In this case, the placenta grows to prevent fetal disease.
The rapid growth of the placenta leads to its premature maturation, and therefore aging. The structure of the placenta becomes lobular, calcifications form on its surface, and the placenta gradually ceases to provide the fetus with the necessary amount of oxygen and nutrients. The hormonal function of the placenta also suffers, which leads to premature birth.
Treatment of placental hyperplasia usually consists of careful monitoring of the condition of the fetus.
Why is the change in the size of the placenta dangerous?
Why are doctors so worried about dramatic changes in the size of the placenta? Usually, in the case of a change in the size of the placenta, functional insufficiency in the work of the placenta can also develop, that is, the so-called feto-placental insufficiency (FPN), problems with the supply of oxygen and nutrition to the fetus will form. The presence of FPN may mean that the placenta cannot fully cope with the tasks assigned to it, and the child experiences a chronic deficiency of oxygen and the supply of nutrients for growth. At the same time, problems can grow like a snowball, the child's body will suffer from a lack of nutrients, as a result, it will begin to lag behind in development and IUGR (intrauterine growth retardation in the fetus) or fetal growth retardation syndrome (FGRS) will form.
To prevent this from happening, it is best to deal with the prevention of such conditions in advance, treating chronic pathology even before pregnancy, so that exacerbations do not occur during gestation. During pregnancy, it is important to control blood pressure, blood glucose levels and protect the pregnant woman as much as possible from any infectious diseases. You also need good nutrition with a sufficient amount of proteins and vitamins.
When diagnosing "placental hypoplasia" or "placental hyperplasia", first of all, careful monitoring of the course of pregnancy and the condition of the fetus is required. You cannot cure or correct the placenta, but there are a number of medications prescribed by your doctor to help the placenta perform its functions.
In the treatment of emerging fetal-placental insufficiency, special drugs are used - trental, actovegin or curantil, which can improve blood circulation in the placenta system both from the mother and the fetus. In addition to these drugs, intravenous infusion of drugs can be prescribed - rheopolyglucin with glucose and ascorbic acid, saline solutions. The development of FPI can be of varying severity and when it is impossible to self-medicate, this can lead to the loss of the child. Therefore, it is necessary to comply with all appointments of an obstetrician-gynecologist.
Changes in the structure of the placenta
The normal placenta has a lobular structure, it is divided into approximately 15-20 lobules of equal size and volume. Each of the lobules is formed from villi and a special tissue that is between them, and the lobules themselves are separated from each other by partitions, however, not complete. If there are changes in the formation of the placenta, new variants of the structure of the lobules may arise. So, the placenta can be two-lobed, consisting of two equal parts, which are interconnected by a special placental tissue, a double or triple placenta can also form, and the umbilical cord will be attached to one of the parts. Also, a small additional lobule can be formed in the normal placenta. Even less often, the so-called "fenestrated" placenta, which has areas covered with a membrane and resembling windows, can occur.
There can be many reasons for such deviations in the structure of the placenta. Most often this is a genetically established structure, or a consequence of problems with the uterine mucosa. Prevention of such problems with the placenta can be active treatment of inflammatory processes in the uterine cavity even before pregnancy, during the planning period. Although deviations in the structure of the placenta do not affect the child so strongly during pregnancy, and almost never affect its development. But in childbirth, such a placenta can cause a lot of trouble for doctors - such a placenta can be very difficult to separate from the wall of the uterus after the baby is born. In some cases, separation of the placenta requires manual control of the uterus under anesthesia. Treatment of the abnormal structure of the placenta during pregnancy is not required, but during childbirth it is imperative to remind the doctor about this so that all parts of the placenta are born, and there are no pieces of the placenta left in the uterus. It is dangerous for bleeding and infection.
Placenta maturity
The placenta, in the course of its existence, goes through four successive stages of maturation:
Placenta maturity 0- normally lasts up to 27-30 weeks. Sometimes at these stages of pregnancy, 1 degree of maturity of the placenta is noted, which can be caused by smoking or drinking during pregnancy, as well as an infection.
Placenta maturity grade 1- from 30 to 34 weeks of pregnancy. During this period, the placenta stops growing, its tissues thicken. This is a crucial period when any deviations can pose a danger to the health of the fetus.
Placenta maturity grade 2- lasts from 34 to 39 weeks of pregnancy. This is a stable period when some advance of the placenta maturity should not cause concern.
Placenta maturity grade 3- normally can be diagnosed starting from the 37th week of pregnancy. This is the stage of natural aging of the placenta, but if it is combined with fetal hypoxia, then the doctor may recommend a cesarean section.
Disorders in the maturation of the placenta
For each stage of placenta formation, there are normal periods in weeks of pregnancy. Too fast or slow passage of certain stages by the placenta is a deviation. The process of premature (accelerated) maturation of the placenta is uniform and uneven. Usually, expectant mothers with a lack of weight face a uniform premature aging of the placenta. Therefore, it is important to remember that pregnancy is not the time to follow various diets, since their consequences can be premature birth and the birth of a weak baby. The placenta will ripen unevenly in case of problems with blood circulation in some of its zones. Usually, such complications occur in overweight women, with prolonged late toxicosis of pregnancy. Uneven maturation of the placenta often occurs with repeated pregnancies.
Treatment, as in fetal-placental insufficiency, is aimed at improving blood circulation and metabolism in the placenta. For the prevention of premature aging of the placenta, it is necessary to carry out measures to prevent pathologies and gestosis.
But delays in maturation of the placenta occur much less often, and the most common reasons for this may be the presence of diabetes mellitus in a pregnant woman, alcohol consumption and smoking. Therefore, it is worth giving up bad habits while carrying a baby.
Placenta calcifications
A normal placenta has a spongy structure, but by the end of pregnancy, some of its zones may become stony, such areas are called petrification or placental calcifications. The hardened areas of the placenta are not able to perform their functions, but usually the remaining parts of the placenta do an excellent job with their task. As a rule, calcifications occur with premature aging of the placenta or prolonged pregnancy. In such cases, the doctor will closely monitor the pregnant woman in order to exclude the development of fetal hypoxia. But usually such a placenta functions quite normally.
Low attachment and placenta previa
Ideally, the placenta should be at the top of the uterus. But there are a number of factors that interfere with the normal location of the placenta in the uterine cavity. These can be uterine fibroids, tumors of the uterine wall, malformations, many pregnancies in the past, inflammatory processes in the uterus or abortions.
Requires more careful observation. It usually tends to rise during pregnancy. In this case, there will be no obstacles to natural childbirth. But it happens that the edge of the placenta, part or all of the placenta overlaps the internal os of the uterus. With partial or complete overlap of the uterine pharynx by the placenta, natural childbirth is impossible. Usually, with an abnormal location of the placenta, a cesarean section is performed. Such abnormal positions of the placenta are called incomplete and complete placenta previa.
During pregnancy, a woman may experience bleeding from the genital tract, which leads to anemia, fetal hypoxia. The most dangerous is partial or complete detachment of the placenta, which leads to the death of the fetus and a threat to the life of the mother. , including sexy, you can not exercise, swim in the pool, walk and work a lot.
What is placental abruption?
What is premature placental abruption? This is a condition when the placenta (normally or abnormally located) leaves the place of its attachment earlier than the due date, that is. With placental abruption, an emergency caesarean section is required to save the life of the mother and fetus. If the placenta has exfoliated in small areas, then doctors try to stop this process, keeping the pregnancy. But even with a slight placental abruption and slight bleeding, the risk of repeated episodes of abruption persists until delivery, and the woman is carefully monitored.
The causes of placental abruption can be trauma or blows to the abdomen, the presence of chronic pathologies in a woman, which leads to problems with blood circulation, defects in the formation of the placenta. Premature placental abruption can cause complications during pregnancy - most often gestosis with increased pressure, protein in the urine and edema, in which all organs and systems of the mother and fetus are affected. It is important to remember that premature placental abruption is the most dangerous complication of pregnancy!
Placental abruption
Rice. 1 - complete placenta previa;
Rice. 2 - regional presentation of the placenta;
Rice. 3 - partial placenta previa
1 - cervical canal; 2 - placenta; 3 - umbilical cord; 4 - fetal bladder
Dense attachment and augmentation of the placenta
Sometimes there are abnormalities not only of the place, but also of the method of attachment of the placenta to the wall of the uterus. A very dangerous and serious pathology is placental augmentation, in which the villi of the placenta are attached not only to the endometrium (the inner layer of the uterus, which exfoliates during childbirth), but also grow deep into the tissues of the uterus, into its muscle layer.
There are three degrees of severity of placenta accreta, depending on the depth of villi germination. In the most severe, third degree, villi grow through the entire thickness of the uterus and can even lead to rupture of the uterus. The cause of placental accreta is inferiority of the endometrium due to congenital defects of the uterus or acquired problems.
The main risk factors for placenta accreta are frequent abortions, cesarean sections, fibroids, as well as intrauterine infections, uterine malformations. Low placentation can also play a role, since in the region of the lower segments, the germination of villi into the deeper layers of the uterus is more likely.
With true placenta accreta, in the overwhelming majority of cases, removal of the uterus with an accrete placenta is required.
An easier case is a dense attachment of the placenta, from an increment of differing depth of penetration of the villi. Tight attachment occurs when the placenta is low or present. The main difficulty with such attachment of the placenta is a delay in its birth or the complete impossibility of independent discharge of the placenta in the third stage of labor. With tight attachment, they resort to manual separation of the placenta under anesthesia.
Diseases of the placenta
The placenta, like any organ, can hurt. It can undergo infection, heart attacks (areas without blood circulation) can develop in it, blood clots can form inside the vessels of the placenta, and the placenta itself can even undergo tumor transformations. But this, fortunately, does not happen often.
Infectious damage to the tissues of the placenta (placentitis) is caused by various microbes that can enter the placenta in different ways. So, they can be brought with the blood stream, penetrate from the fallopian tubes, ascending from the vagina, or from the uterine cavity. The process of inflammation can be extended to the entire thickness of the placenta or occur in some of its areas. In this case, the treatment should be specific, and it depends on the type of pathogen. Of all the possible drugs, the one that is acceptable for pregnant women in a given period will be selected. And for the purpose of prophylaxis before pregnancy, it is necessary to carry out a full therapy of chronic infections, especially in the genital tract.
Placental infarction usually develops, like any other, as a result of prolonged ischemia (vasospasm of the placenta vessels), and then the parts of the placenta that receive blood from these vessels die as a result of oxygen deficiency. Usually, heart attacks in the placenta occur as a result of a severe course of gestosis or with the development of hypertension of a pregnant woman. Placentitis and placental infarction can cause FPI and fetal developmental problems.
Sometimes, as a result of inflammation or damage to the vascular wall, with a violation of blood viscosity or with sudden movements of the fetus, blood clots form inside the placenta. But small blood clots do not affect the course of pregnancy in any way.
As a result of the changes described above, the sensitivity of a pregnant woman's body to pharmacological drugs changes. Of great importance for the rational use of pharmacological agents used to provide anesthetic aid to pregnant women are also the features of the transplacental transition of one or another pharmacological agent.
It is known that the transplacental transition of various pharmacological substances is carried out by diffusion, active transport and transport through the chorionic villi. The degree and rate of transfer of medicinal substances through the placenta depend on the total surface of the placental membrane and its thickness, the intensity of the uteroplacental circulation, gestational age, molecular weight of pharmacological substances, the ability of the drug to dissolve in lipids, connection with proteins and a number of other points.
The paraplacental transition of pharmacological substances is also not excluded. At the same time, the role of amniotic fluid is emphasized, which not only contributes to the elimination of metabolic products, but can also participate in the supply of the fetus with the necessary substrates, as well as in the metabolism of drugs used in pregnant women. Moreover, the paraplacental transfer of substances ends, as a rule, simultaneously with the rupture of the membranes.
For drugs used in obstetric anesthesiology, the concentration gradient in combination with the volume of placental blood flow is of no small importance; molecular weight of pharmacological substances. Substances with a molecular weight below 600 (gases, crystalloid solutions, etc.) pass through the placental barrier freely. The permeability of substances with a molecular weight of more than 600 is less pronounced. However, if the placenta permeability is impaired, substances weighing 40,000-80,000 and their metabolites can penetrate the placental barrier.
The degree of ionization of drug molecules is also important. Ionized substances penetrate the placenta to a lesser extent than non-ionized ones. The latter, especially readily soluble in lipids (ether, fluorotan, etc.), neurotropic, analgesics easily penetrate the placenta. Muscle relaxants, poorly soluble in fats and being high-molecular compounds, are largely retained by the placental barrier, some of them still enter the fetus.
A significant role is played by the characteristics of the fetus associated with age, the functional state of the nervous, endocrine, enzymatic systems, as well as other factors that determine the reactivity of the fetus. In newborns, a slow metabolism is noted. Of no small importance is the ability of pharmacological agents to bind to blood plasma proteins. Erythrocytes are also involved in the transfer of drugs, but their role is insignificant, since their surface is 200 times smaller than the surface of the protein. In newborns, plasma proteins have a lower ability to bind drugs than in an adult woman's body. At the same time, the distribution of drugs in newborns, especially in low birthweight children, differs from adults due to immaturity and increased permeability of membranes, especially the blood-brain barrier. The distribution of medicinal substances in newborns is also influenced by the volume of the extracellular space. So, in newborns, it is about 40% of the body weight, in adults - 20%. In an immature fetus, the brain contains less myelin, which causes an increased sensitivity of the fetal nerve formations to the effects of any pharmacological agents, including drugs and neurodepressants. In this regard, newborns often experience various negative side reactions to pharmacological drugs administered to the mother.
When using pharmacological agents in a pregnant woman, it is necessary to take into account the concentration gradient. It is known that the higher it is, the lower the molecular weight of a drug, the faster the equilibrium of concentrations of this drug in the mother and fetus will be achieved.
A decrease in the volume of circulating blood (bleeding, preeclampsia) with a simultaneous decrease in protein fractions also leads to the fact that pharmacological drugs circulate at higher concentrations and most of them are in a state not associated with proteins, and therefore drugs penetrate the fetus at higher concentrations ...
The nature of the contractile activity of the uterus also has a great influence on the penetration of pharmacological preparations. With vigorous labor, intrauterine pressure can reach rather high numbers (70-80 mm Hg) with a simultaneous sharp increase in intra-amnial pressure, which exceeds the pressure in the arterial vessels of the uterus. Violent labor can cause a complete cessation of the flow of arterial blood into the intervillous space, thereby preventing the passage of pharmacological drugs across the placental barrier.
It is known that when the mother is injected with multidirectional pharmacological drugs, about 1 / 2-2 / 3 of the blood from the placenta passes through the fetal liver. There, the inactivation of most of the medicinal substances used by the pregnant woman takes place. As a result, the concentration of some pharmacological agents in the fetal liver is tens of times higher than their concentration in the brain and other tissues of the fetus. Moreover, the blood leaving through the portal system is diluted with blood coming from the intestinal vessels and before entering through the left atrium and then to the brain, the concentration of the drug is significantly reduced. In addition, about 50% of the total cardiac output returns to the placenta without reaching the fetal tissue due to ductal shunting. Thus, the tissues of the fetus receive only about half of the drug that penetrates into its blood through the placental barrier.
The above data must be taken into account when anesthetizing childbirth, as well as when carrying out anesthesia during operative delivery. Currently, the main way to prevent and relieve pain is the use of drugs. The term "pain relievers" is used to refer to substances that stop pain sensitivity. The classification of pain relievers can be summarized as follows.
I. Opioid (narcotic) analgesics:
A) opioid receptor agonists (morphine, sufentanil);
B) agonists-antagonists and partial agonists of opioid receptors (buprenorphine, butorphanol, nalbuphine, pentosacin).
Opiates are substances derived from opium. Their pharmacological action is due to their interaction with opioid receptors in the central nervous system and peripheral tissues. Opioid receptor agonists have significant analgesic properties. Under the influence of these drugs, the pain perception threshold increases, weakening the emotional-behavioral responses to pain. Their analgesic effect is due to the influence on the interneuronal transmission of (pain) impulses at the permitted levels of the central nervous system. There is another concept according to which the analgesic effect is due to peripheral receptors.
Agonists - antagonists and partial agonists of opioid receptors differ from substances from the group of agonists as follows. With an increase in their doses, the analgesic effect and respiratory depression increase to a certain limit, and then the narcogenic potential is much lower, that is, this group of substances is safer than morphine and similar drugs, but in some cases it may be inferior to them in effectiveness.
Pentazocine at a dose of 30-60 mg causes analgesia corresponding to the effect of morphine at a dose of 10 mg (average therapeutic dose). An increase in the dose of more than 30 mg usually does not lead to respiratory depression, however, dysphoria and other psychomimetic effects may appear. At the same time, unlike morphine, pentazocine can cause an increase in blood pressure and tachycardia. In this regard, this drug should be used with caution in cardiovascular pathology.
Nalbuphine is pharmacodynamically similar to pentazocine.
Buprenorphine strongly binds to opioid receptors, its effect is longer than that of morphine (about 6 hours). Analgesic doses are an order of magnitude less (0.3-0.6 mg).
In terms of effectiveness, speed of onset of effect, duration of action (4-6 hours), butorphanol is closer to morphine, but is used in smaller doses (2 mg); a negative property is an increase in blood pressure.
II. Centrally acting non-opioid drugs with analgesic activity.
These include:
1. Clonidine and guanfacine. Clonidine has a fairly pronounced analgesic property. Its feature is the ability to prevent unfavorable hemodynamic disturbances in painful sensations, without causing drug dependence and without adversely affecting the respiratory function. At the same time, the analgesic effect may be accompanied by hypotension, less pronounced with the epidural administration of clonidine. Guanfacine differs from the latter in greater receptor activity and in all its properties is close to clonidine.
2. Blockers of sodium channels (membrane stabilizing agents). These include carbamazepine, diphenin. These drugs, blocking the sodium channels of neutron membranes in the nuclei of the trigeminal nerve, reduce the activity of the generator of pathologically enhanced excitation. As a result, in the membranes of the afferent fibers of the trigeminal nerve, impulse decreases, which forms the pain syndrome. These drugs also have antiepileptic properties.
3. Inhibitors of neuronal reuptake of monoamines (serotonin, norepinephrine) amitriptyline, imizine. The analgesic properties of tricyclic antidepressants were discovered in the early 1960s. The analgesic effect is associated with the inhibition of the reverse neuronal uptake of monoamines in the corresponding synapses of the brain. As a result, segmental and supraspinal mechanisms for controlling pain impulses are enhanced.
4. Antagonists of excitatory amino acids (ketamine, dextromethorphan, memantine). Ketamine, a non-competitive NMDA receptor antagonist, has significant analgesic properties. In situations of acute pain, the analgesic effect of ketamine when administered into a vein usually develops within 10 minutes and lasts 2-3 hours. Ketamine causes an increase in blood pressure and increased heart rate with an increase in its minute volume. Hallucinations and other mental disorders are common side effects. Memantine and dextrometrophan, which do not have such side effects as ketamine, appear to be more promising agents from the group of excitatory amino acid antagonists.
5. Nitrous oxide. The analgesic effect of nitrous oxide, corresponding to 10 mg of morphine, is manifested by inhalation of gas at a concentration of 30-50%. The low lipophilicity of the compound leads to a rapid onset of action and its equally rapid disappearance after the cessation of inhalation. Consideration should be given to the inhibitory effect of nitrous oxide on bone marrow function during prolonged inhalation due to inhibition of methionine synthase. Inhalation of nitrous oxide in analgesic concentrations should be limited to 6 hours.
6. Blockers of histamine H1-receptors (diphenhydramine). Histamine plays an important role in peripheral nociceptive mechanisms, but the role of CNS histaminergic neurons in pain perception and control is unclear. Blockers of histamine H1 receptors are quite effective for moderate pain after surgery, during childbirth.
7. GABA-B-mimetics (baclofen) are similar in chemical structure to gamma-aminobutyric acid. The main pharmacological effect of baclofen is antispastic: by inhibiting spinal reflexes, it reduces muscle tension. In terms of effectiveness, it is inferior to sodium channel blockers.
8. Blockers of calcium channels L-type (verapamil, nimodipine) and blockers of N-type channels SNX-III. Calcium ions are involved in the regulation of pain sensitivity at different stages of the transmission of nociceptive signals. In this case, the calcium channels of the membranes are blocked, which leads to a decrease in the current of calcium ions at the end of the primary afferents in the spinal cord and, accordingly, to the suppression of the release of mediators.
9. Inhibitors of cyclooxygenase (COX) mainly in the central nervous system - non-narcotic analgesics. The latter include salicylates, pyrazolone derivatives (amidopyrine, analgin, etc.) and paraminophenol (phenacetin, paracetamol). Non-narcotic analgesics are inferior to opioids in terms of the severity of the analgesic effect; they are less effective for intense pain. Their analgesic effect is manifested mainly in moderate pain associated with inflammatory processes. Non-narcotic analgesics do not cause euphoria, drug dependence, do not depress breathing.
Non-narcotic analgesics have analgesic and antipyretic effects. These effects of non-narcotic analgesics are associated with the fact that they inhibit the activity of COX, under the influence of which prostaglandins are formed in tissues from unsaturated fatty acids, which are involved in the processes of pain, inflammation and fever. Acting on painful nerve endings, prostaglandins increase their sensitivity to bradykinin, a peptide formed in tissues during inflammation simultaneously with prostaglandins and which is a stimulant of pain endings. By inhibiting the synthesis of prostaglandins, non-narcotic analgesics reduce the sensitivity of nerve endings to bradykinin. They can be used successfully for pain relief during labor.
At the present stage of development of anesthesiology in obstetrics, drugs of various groups have become widespread. Let us dwell on the drugs most widely used in practice.
Propanidide (sombrevin, epantol) - when administered intravenously, partially binds to plasma proteins, rapidly decomposes into inactive metabolites, after 25 minutes. after administration, it is not detected in the blood, it is excreted through the lungs, with urine and feces. The narcotic effect occurs 20-40 after the introduction of sombrevin. The surgical stage of anesthesia lasts 3-5 minutes. Propanidide has a more pronounced hypnotic effect than analgesic. After 10-20 s after the start of intravenous administration, consciousness is lost, breathing becomes more frequent and deepens. Blood pressure decreases, pulse rate increases by 20-40 per minute. After the phase of increased bioelectric activity, a stage of displaced waves occurs with a predominance of high-amplitude delta and theta rhythms, and then signs of an increasing depression of the bioelectric activity of the brain appear. Cardiac output decreases, peripheral vascular resistance and systemic arterial pressure decrease, cardiac output increases. Sombrevin crosses the placental barrier, but after 15 minutes it decomposes into inactive metabolites. There is evidence that the drug can lead to respiratory depression, acidosis in the fetus, and cause histamine-like reactions in the mother.
Ketamine hydrochloride (calypsol, ketalar) has a half-life of about 2 hours. After intravenous administration, the narcotic effect occurs after 30 seconds and lasts 5-10 minutes, after intramuscular administration - after 3-5 minutes and lasts 12-15 minutes. Possessing a strong analgesic effect, it does not relax skeletal muscles and does not inhibit reflexes from the respiratory tract. In pregnant women, it increases the tone of the uterus. With its introduction, the laryngeal and pharyngeal reflexes are preserved, there is a tendency to an increase in blood pressure by 20-25% from the initial level, an increase in heart rate by 20-30%. According to the literature, ketamine is able to stimulate the adrenal cortex, causing ACTH and GHB-like effects. When using ketamine, there is no negative effect on gas exchange, and oxygen consumption by the brain decreases in conditions of massive blood loss. The drug penetrates the placental barrier and, in doses of more than 1.2 mg / kg of body weight, causes depression of the vital functions of the fetus.
There is evidence that sombrevin and ketalar also affect the body's immunological system. So, with the introduction of sombrevin, the number of T- and B-lymphocytes decreases by 15 and 4%, respectively, while with the introduction of ketalar, their increase occurs (by 10 and 6%, respectively), which indicates a lesser danger of using ketalar in patients with allergic diseases, blood loss and deficiency of the immune system. This is important, since during pregnancy there is a shift in the immune system of the mother's body, which consists in a decrease in cellular and humoral immunity. In addition, a number of immunological systems are directly related to perinatal damage to the central nervous system of the fetus.
Barbiturates (thiopental sodium, hexenal). After intravenous administration, 65-70% of the dose of barbiturates binds to plasma proteins, and the remaining free fraction acts narcotic. The narcotic action of barbiturates is based on inhibition of the cerebral cortex and blockade of synapses (inhibition of the synthesis of acetylcholine and other mediators) of the ascending part of the activating system of the brain stem, increasing the excitability threshold of nerve cells by reducing the permeability of the membrane potential, and prolonging the period of cell refractoriness. They practically do not affect the contractile activity of the uterus, reduce cardiac output, which is due to the suppression of sympathetic-adrenal activity, a direct effect on the myocardium.
The analgesic phase of anesthesia is usually not pronounced and after 30-60 seconds loss of consciousness occurs; there is no excitement, there is an increase in the pharyngeal, laryngeal and ocular reflexes.
Barbiturates - weak acids, having a low molecular weight, penetrate the placental barrier, and the degree of fetal depression is directly proportional to the concentration of the anesthetic in the mother's blood. Barbiturates reduce the level of bilirubin in newborns and are successfully used in hypoxic conditions of the body in general anesthesiology.
Sodium hydroxybutyrate (sodium salt of gamma-hydroxybutyric acid GHB) is similar in action to gamma-aminobutyric acid, a mediator of inhibition of the central nervous system. It is well absorbed, within 4 hours only 10% of the drug is released, the rest of its amount is utilized as an exchange substrate, 98% is released through the lungs in the form of carbon dioxide. The mechanism of action of GHB is closely related to carbohydrate metabolism. As a precursor of gamma-aminobutyric acid, it promotes the occurrence of inhibitory processes in the brain tissue. By interfering with metabolic processes, it protects the body from the harmful effects of oxygen deficiency. With the introduction of GHB, a decrease in cerebral blood flow velocity by 11% is noted. The drug greatly potentiates the action of other analgesics and drugs.
Narcotic action of GHB of cortical origin. Anesthesia occurs only with deep anesthesia, which is accompanied by vegetative shifts in the form of hypotension, bradycardia, respiratory depression and severe muscle relaxation while maintaining eye reflexes. It has a pronounced hypothermic effect without complications characteristic of hypothermia (heart rhythm disorders). Does not violate energy metabolism, phosphorylation processes of respiration, brain and other tissues.
GHB penetrates the placental barrier and is widely used in obstetrics for the treatment of fatigue in childbirth, for pain relief.
Due to its high solubility in water, Droperidol is well and quickly absorbed. Plasma proteins bind about 90% of the drug. The maximum concentration in blood plasma is determined 2-6 hours after oral administration and 10-60 minutes after intramuscular injection and remains high for about 3 days. Droperidol changes little in the body, is metabolized mainly in the liver, 15% of the drug is excreted in the bile. Excretion of droperidol is slow: in 5 days, the kidneys excrete only 40% of a single dose administered. During natural childbirth, droperidol is practically not detected in the blood of a newborn, with a caesarean section, the concentration of droperidol in the blood is 3 10-6-6 10-6 mg / ml, and in the blood of a newborn 5 10-7 - 8 10-7 mg / ml, not causes oppression of the fetus. With the introduction of droperidol, blood oxygen saturation decreases, the minute volume of respiration increases by 1%, and the activity of neuropeptides increases.
It has an antiemetic effect, lowers body temperature, and is a pronounced anticonvulsant agent. Possessing an adrenolytic effect, it improves peripheral blood circulation, eliminating vascular spasms. Potentiates the effect of narcotic analgesics, especially fentanyl.
Sibazone (Relanium, seduxen, diazepam) is absorbed when taken orally in an amount of about 75%, the maximum plasma level is observed after 1-1.5 hours. Plasma proteins bind about 98% of sibazone.
The half-life in the blood plasma of a woman is 1-3 days, in newborns - 31 hours. The mechanism of action is associated with an increase in the activity of endogenous gamma-aminobutyric acid. The sedative and anticonvulsant effects usually last long in pregnant women, since the elimination period is somewhat longer than in non-pregnant women. In the blood of the fetus, the highest concentration is created 5 minutes after intravenous administration. In the blood of the umbilical cord of a newborn, the concentration of sibazon is equal to that in the venous blood of the mother when it is administered at a dose exceeding 10 mg or more. At the same time, the concentration of the drug in the brain is low. At the same time, the occurrence of apnea in newborns, hypotension, hypothermia, and sometimes signs of neurological depression are not uncommon. With prolonged use of sibazon, respiratory depression in newborns and the transition of respiratory acidosis to metabolic is possible. This is due to the rather high level in the child's blood of both the drug itself and its active metabolite N-desmethyldiazepam. Sibazon is able to accelerate the dilatation of the cervix, helping to relieve anxiety in a number of women in labor.
Promedol is easily absorbed by any route of administration. The maximum plasma concentration is determined after 1-2 hours. After intravenous administration, the plasma concentration decreases within 1-2 hours. About 40% of promedol binds to plasma proteins, where it is mostly rendered harmless. In the body, it is hydrolyzed to meperidine and normal-peridic acids, followed by conjugation. A small amount is excreted by the kidneys unchanged.
The mechanism of action of promedol is based on interaction with opiate receptors. It has an analgesic, sedative effect, depresses the respiratory center. After parenteral administration, the analgesic effect occurs after 10 minutes and lasts 2-4 hours. In addition to the analgesic, it has an antispasmodic effect, promoting the opening of the cervix. Easily penetrates through the placenta. In 2 minutes after intravenous and somewhat later after intramuscular injection, the concentration in the umbilical cord blood is approximately equal to that in the mother's blood plasma. However, there may be significant fluctuations in individual fetuses, depending on their prenatal state. The maximum concentration of promedol and its toxic metabolite, norpetidine, in the blood plasma of a newborn is observed 2-3 hours after its administration to the mother. The half-period of elimination of promedol from the body of the newborn is 22.7 ± 3.2 hours, in the mother, 2.53 ± 0.6 hours.
Promedol is usually safe for both mother and baby. However, in some cases, the drug can cause depression in the newborn due to the fact that it has a suppressive effect on the processes of glycolysis and the respiratory center.
Fentanyl is an agonist of opioid receptors and surpasses morphine in its analgesic activity by 200-400 times. The short duration of the effect of fentanyl is due to the rapid metabolism of the compound, as well as its redistribution in the body. Biotransformation of fentanyl occurs mainly in the liver. It is excreted by the kidneys and through the gastrointestinal tract mainly in the form of metabolites and partially unchanged. Penetrating through the placental barrier, it can cause drug depression in the fetus.
Pentazocine - belongs to the group of opioid receptor agonist antagonists and at a dose of 30-50 mg. causes analgesia corresponding to the effect of morphine at a dose of 10 mg. Moreover, an increase in the dose of more than 30 mg does not lead to respiratory depression, however, the incidence of dysphoria and other psychomimetic effects increases. Pentazocine can cause an increase in blood pressure, tachycardia (not recommended in women with cardiovascular disease and high hypertension).
Diprivan (propofol) is a new ultra-short-acting intravenous anesthetic. In 1993, it was registered by the Pharmaceutical Committee of the Ministry of Health of the Russian Federation and approved for clinical use in our country. Practical experience in the use of propofol has been accumulated abroad (more than 40 million anesthetics have been performed) both for short and long-term surgical interventions in almost all areas of medicine.
Diprivan quickly induces sleep, maintains the deactivation of consciousness throughout the infusion of the drug with a rapid recovery of consciousness after cessation of its administration, interacts well with narcotic analgesics and antipsychotics, and has less side effects compared to other intravenous anesthetics. However, a number of publications indicate the possible undesirable manifestations of diprivan during anesthesia, including the deterioration of some parameters of central hemodynamics, although the data on this issue are extremely contradictory.
In foreign literature, all drugs administered intravenously during anesthesia have one general term - "intravenous anesthetics". In the strict sense of this term, diprivan is not an anesthetic, since it does not have any pronounced analgesic properties, but is only able to increase the pain threshold, as, for example, most ataractics and tranquilizers. Therefore, from the point of view of pharmacology, Diprivan is not an anesthetic, but a hypnotic.
A very valuable quality of Diprivan is its ability to induce good muscle relaxation. The muscle relaxant effect of diprivan really exists. This is confirmed by a significant number of publications, some of which report the possibility of tracheal intubation without the use of muscle relaxants. It should be noted and the good ability of the drug to suppress the laryngeal-pharyngeal reflexes. This circumstance also explains the fact that foreign anesthesiologists consider propofol an ideal means for the introduction of a laryngeal mask - a modern means of maintaining airway patency, both under conditions of spontaneous breathing and during mechanical ventilation. The other side of the muscle relaxant effect of diprivan is also known - the ability to reduce muscle hypertonicity and even convulsive syndrome.
All undesirable effects of diprivan can be divided into 2 groups:
1) complications arising during or after anesthesia,
2) complications that can occur as a result of the use of diprivan during intensive care.
After anesthesia, agitation, severe asthenia, intracranial hypertension, somnolence, tremors, hallucinations, and neurological disorders may occur. Allergic reactions after using the drug are rare.
Nitrous oxide is one of the components of general anesthesia for caesarean section. The drug is insoluble in lipids, dissolves in blood plasma up to 23 vol.%. Very quickly (2-3 minutes) is absorbed and excreted by the lungs unchanged. 5-10 minutes after the start of inhalation, the saturation of tissues with anesthetic reaches a maximum. It is completely eliminated from the blood in 5-6 minutes.
A relatively weak anesthetic with a high degree of safety in a mixture with oxygen at a concentration of 50 vol.% Causes analgesia without loss of consciousness and changes in reflex excitability. At a concentration of 50-70 vol.% It causes euphoria, laughter, confusion. It has an effect only on the central nervous system, does not depress respiration, the cardiovascular system, does not adversely affect the liver, kidneys, metabolism, uterine contractile activity. It quickly penetrates the placenta, after 2-19 minutes the concentration of nitrous oxide in the blood of the umbilical cord vein is 80%, with longer inhalation - 90% of the level in the mother's blood. Prolonged inhalation of nitrous oxide is sometimes accompanied by the birth of a child with a low Apgar score, which is considered as a consequence of increased release of catecholamines by nitrous oxide in the mother's body and vasoconstriction in the uterus in response to inhalation. There is evidence that nitrous oxide is able to protect the brain from ischemic damage, although to a lesser extent compared to isoflurane, halothane and improves uteroplacental circulation and cerebral oxygenation.
M-anticholinergics (atropine, metacin) practically do not penetrate into the central nervous system and are only capable of eliminating smooth muscle spasm. It is usually used as an adjunct to sedation to relieve the side effects of the anesthetic used. They penetrate the placental barrier, do not adversely affect the condition of the fetus and newborn.
Relaxants (ditilin, listenone, muscle relaxants, etc.) are slowly and not completely absorbed in the digestive tract. Do not cross the placenta. They have muscarinic and nicotine-like effects. They cause persistent depolarization of the subsynaptic membranes in myoneural synapses, disrupting the transmission of starting impulses from the axons of the somatic nerves to the muscle fibers, as a result of which they relax. They do not violate the functions of the liver and kidneys, do not affect the coagulation and anticoagulation systems of the blood. These relaxants do not affect the state of the newborn, but in some newborns with impaired fetal-placental permeability, some authors note a low Apgar score.
The positive and negative aspects of the pharmacological agents used in obstetric anesthesiology listed in this chapter do not occur in all women in labor and fetuses. The frequency of possible manifestations of each of these drugs depends on many circumstances and primarily on the state of health of the woman herself, the presence or absence of violations of the fetoplacental complex, obstetric pathology and other factors. As can be seen from the data presented, all drugs mainly penetrate the placental barrier, influencing not only the condition of the mother, but also the condition of the fetus and newborn.
3.4. Pain relief for physiological and complicated labor
Currently, non-drug and medication methods are used to relieve pain during labor (Scheme 3).
Non-drug methods of pain relief during labor
The goal of psychoprophylactic preparation of a pregnant woman for childbirth is to remove the psychogenic component of labor pain, eliminate the idea of its inevitability, an oppressive feeling of fear and contribute to the creation of a new concept of childbirth as a favorable physiological process in which pain is not required. Exposure to the cerebral cortex during psycho-preventive training helps to reduce pain. Women in labor who have undergone psychoprophylactic preparation for childbirth require a lower dose of medication for pain relief during childbirth. The method was proposed in our country by I.Z. Vel'novsky and K.I. Platonov in 1940.
An important psychological moment is the presence of a husband or another person close to the woman in labor during childbirth, if there is mutual consent. It is useful for the pregnant woman to meet in advance with the doctor and midwife who will lead the birth.
The method of psychoprophylactic training requires painstaking, long-term individual preparation of a pregnant woman for childbirth, taking into account the knowledge acquired by the woman in labor during childbirth (selective muscle relaxation, breathing regulation).
In practical health care, the choice of method of pain relief for childbirth is often approached in a stereotyped manner and decided during the process of childbirth. However, in childbirth, it is difficult to determine the psychoemotional state of the woman in labor in order to choose an adequate method of pain relief. Among non-drug methods, methods that reduce painful stimuli deserve attention. These include freedom of movement of the woman in labor, counterpressure on the nerve endings, and abdominal decompression. Of the above methods, the first two can be successfully used.
Considerable attention is paid to methods that activate peripheral receptors. Among these methods, attention is paid to hydrotherapy (warm baths), acupuncture and acupressure, percutaneous electroneurostimulation, etc.
Warm baths activate the temperature and tactile receptors of the skin, which inhibits the transmission of impulses to the cortex. The centers of the brain (thalamus and cortex) send inhibitory impulses to the dorsal column and inhibit the transmission of pain signals. Hydrotherapy reduces pain, provides relaxation, reduces physiological tension and pressure on the abdominal muscles, allows the uterus to contract more efficiently, and improves oxygenation.
The disadvantages of the method of childbirth under water include the difficulties of ensuring asepsis, tracking the nature of the contractile activity of the uterus and the fetus, the moment of the outflow of amniotic fluid, etc.
Touching and massage during childbirth is widely practiced in a number of countries. Various types of massage stimulate skin receptors, increase the neural activity of many myelin fibers. These stimuli are transmitted more quickly than painful ones. The action of "bombarding" the central nervous system reduces pain.
Many clinics use acupuncture and acupressure to relieve pain during labor. Acupuncture blocks the sensory and emotional components of pain, but the mechanism of action is not clear enough. The following acupuncture recipe is effective for pain relief in the first stage of labor on the anterior abdominal wall (VCH-guan-yuan), in the area of the hand (GI4-xe-ry), in the upper third of the lower leg (E36-tszu-san-li) in the lower third of the lower leg (RP6 - san-yin-jiao).
In the second stage of labor, it is effective to use biologically active points in the sacrum area (V31 and V34-baliao).
Acupressure is essentially “acupuncture without needles” that achieves pain relief.
Acupuncture and acupressure help relieve pain during labor, normalize labor and do not adversely affect the fetus. This method limits the motor activity of the woman in labor and requires careful monitoring, and therefore the session is limited in time.
Transcutaneous electroneurostimulation (TENS) has been successfully used to relieve labor pain. For this purpose, the domestic device "Delta-101" is used, it is a single-channel electrostimulator that generates asymmetric bipolar impulses. The pulse repetition rate is 30-120 Hz, the current is 10-60 mA, the pulse duration is 0.5-0.8 ms. To achieve the greatest effect, 2 devices "Delta-101" are used simultaneously. Two pairs of lead electrodes in the form of plates with an area of 20 cm2, treated with an electrically conductive paste, are fixed with an adhesive plaster in the zone of maximum pain on the skin of the anterior abdominal wall (trigger zones of the uterus) and posteriorly paraverted in the zone of segmental innervation TX-LII.
With this technique, afferent fibers are “bombarded” and the gate is “closed” for pain. It is believed that this increases the level of endorphins in the cerebrospinal fluid. According to our data, the analgesic effect is achieved in 80.6% of women.
TENS has no negative effect on the contractile function of the uterus, fetal cardiac activity, and the condition of the newborn.
There is a positive experience with the use of a water block for pain relief in labor. To do this, 0.1 ml of sterile water is injected intracutaneously at four points in the region of the sacrum edge, or near it, a decrease in pain is noted within 2 hours. The mechanism of action is the same as when carrying out transcutaneous electrical stimulation.
In 1955, O. Heyns proposed to use abdominal decompression for pain relief during labor. According to the author, this technique increases placental blood flow, fetal oxygenation, and labor pain decreases. The method is not devoid of global action and complications, and therefore did not receive widespread distribution.
The role of hypnosis in pain relief in labor has long been proven. But a prerequisite is a good command of this technique.
Focusing and distracting the attention of women in labor are effective in relieving pain in labor: and for this purpose, music, television and other factors are used.
Music contributes to distraction, relaxation, rhythm of breathing, a smaller dose of medication is required. According to Goldstein (1980), it promotes the production of endophyrin and thus reduces pain.
In the foreign literature there is an experience of audioanalgesia, that is, the use of noise ("noise of the sea", "noise of an incident wave") for pain relief in labor. During labor, a woman in labor increases the strength of the sound, which serves as a distraction.
Non-drug methods require time, effort in teaching techniques (a specialist), their effectiveness is unpredictable to a greater extent due to the complexity of the pain system and the characteristics of the human body. In case of insufficient anesthesia, the appointment of medications is required, but in a lower dose.
Medical methods of pain relief in labor
The use of drugs for the treatment of pain and anxiety in women in labor involves the use of anesthetics and analgesics, both narcotic and non-narcotic, and their combination with sedatives and antipsychotics. In recent years, the arsenal of drugs for pain relief in childbirth has grown significantly. It includes sedatives, numerous derivatives of the phenothiazine series, benzodiazepines, antispasmodics, the latest analgesics of various structures.
One of the most commonly used analgesics is promedol. 20 mg of the drug is injected intramuscularly, the duration of its action is 1.5-2 hours. After its introduction, the fetal heart rate may become monotonous, labor is preserved. However, in doses of more than 40 mg, promedol inhibits respiration and causes severe drug dependence. In addition, it is able to cause a state of stunnedness, nausea, vomiting, causes atony of smooth muscles, constipation. The described side effects are inherent in almost all potent analgesics, with the exception of pentazocine (Lexir, Fortral).
The drug is effective for pain relief during labor and is safe for the fetus and newborn. 30 mg of pentazocine produces the same degree of analgesia as 10 mg of morphine or 100 mg of promedol. It is also known that pentazocine has a stimulating effect on hemodynamics and respiration, and hysterographic data indicate its rhodostimulating effect. The drug, however, does not have any pronounced sedative effect. It is considered to be non-narcotic, incapable of causing drug addiction.
Tramal (50-100 mg / m) is currently successfully used to relieve spontaneous childbirth, which does not adversely affect the course of labor and the condition of the newborn. Sometimes there is depression in the newborn and vomiting in the pregnant woman.
Moradol at a dose of 0.025-0.03 mg / kg of body weight is an effective means of pain relief during labor. The analgesic effect, as in the above drugs, occurs in 15-20 minutes; the duration of its action is on average 2 hours. Moradol does not adversely affect the fetal circulatory function and the contractile activity of the uterus.
The method of neuroleptanalgesia, which provides a kind of mental peace, satisfactory analgesia, accompanied by stabilization of hemodynamic parameters and the absence of a significant effect on the nature of labor and a negative effect on the condition of the fetus and newborn, has become quite widespread for labor pain relief.
Fentanyl is administered intramuscularly at a dose of 0.5-1.0 ml of a 0.005% solution. The greatest effect is achieved when it is combined with droperidol 2.5-5.0 mg (1-2 ml). If necessary, a repeated dose is administered every 3-4 hours. Neuroleptanalgesia should not be used if patients have severe hypertension of the pulmonary circulation, increased tone of the bronchioles, and ventilation failure. You should be prepared for the possibility of developing drug-induced depression in the newborn. In this regard, an attempt was made to use the so-called "pure antagonist" naloxone in childbirth in order to eliminate the depressive effect of narcotic analgesics on the respiratory function of newborns.
Another common method of pain relief in labor is the ataralgesia method - the combined use of analgesics with 5-10 mg of sibazone, seduxen, etc. Since benzodiazepine derivatives are among the safest tranquilizers, their combination with analgesics is especially indicated for severe fear, anxiety and mental stress of the woman in labor.
The combination of dipidolor with seduxen has a beneficial effect on the course of labor, helps to shorten the total duration of labor and the period of cervical dilatation.
Schematically, the sequence of actions when carrying out pain relief during childbirth can be represented as follows:
At the beginning of labor (latent phase of labor, cervical dilatation by 3-4 cm with relatively painless contractions to relieve tension, fear), the use of tranquilizers is indicated (trioxazine 0.3-0.6 g, Elenium 0.01-0.015 g, seduxen 0.01 g, etc.);
With the development of regular pain in the contractions, the combined or independent use of inhaled or non-inhalation analgesics in combination with sedatives or antispasmodics is indicated. In easily suggestible women in labor, it is possible to use acupuncture, therapeutic electroanalgesia, percutaneous electroneurostimulation;
With the ineffectiveness of these methods of labor pain relief or in the presence of extragenital pathology, gestosis, discoordinated labor activity, it is advisable to use long-term epidural (epidural) anesthesia.
In practice, a combination is often used
Painkillers, sedatives and antispasmodics. The following recipes can be recommended:
1) promedol 20-40 mg + no-spa 40 mg,
2) promedol 20-40 mg + seduxen 10 mg + papaverine 20-40 mg,
3) moradol 1-2 mg + seduxen 10 mg + no-shpa 40 mg,
4) tramal 100 mg + diphenhydramine 20 mg + no-spa 40 mg with a frigid cervix - metacin 1 ml 0.1%.
After the introduction of these combinations of drugs, the fetal heart rate is monotonous (according to ECG data), pain is noted in 30-60% of women in labor. Attempts to achieve complete anesthesia by significantly increasing the doses of analgesics or reducing the intervals between injections are fraught with the risk of developing weakness in labor, increased blood loss during childbirth, and narcotic depression of the fetus.
Epidural analgesia
The desire to achieve a full-fledged analgesic effect in labor pain relief with minimal impact on the body of the mother and newborn contributed to the emergence of interest in the use of epidural analgesia for labor pain relief, since its pronounced analgesic and antispasmodic effect is combined with the absence of a depressing effect on the functions of the respiratory system, heart, liver, kidneys.
The method of epidural analgesia in labor has been studied quite fully. There is a large amount of information about the positive effect of epidural analgesia on the birth act, the absence of a negative effect on the fetus and newborn. The beneficial effect of epidural analgesia during pregnancy and childbirth complicated by preeclampsia is important. The positive role of epidural analgesia in pain relief of labor in breech presentation of the fetus has been established.
Epidural analgesia has a beneficial effect on the course of preterm labor, shortening the period of cervical dilatation and lengthening the period of expulsion, which contributes to a smoother movement of the fetal head. At the same time, the muscles of the perineum relax and the pressure on the head decreases.
It was found that in women in labor who received anesthesia of labor with narcotic analgesics, children are born with neuroreflex activity significantly worse than in mothers who received epidural analgesia during labor.
At the same time, the latter can be the reason for a decrease in the activity of the uterus due to a decrease in aortocaval compression. There was also an increase in the duration of labor and a decrease in uterine activity in the second stage of labor, which contributes to an increase in the number of operative births. It is also known about the negative hemodynamic effect of epidural analgesia in childbirth, associated with the development of peripheral vasodilation, which in turn leads to a decrease in venous return, the emergence of the Bainbridge reflex and bradycardia. In addition to the described possible negative effects of epidural analgesia, such as hypotension of the bladder and hyperthermia have been noted.
For epidural analgesia, both local anesthetics and narcotic and non-narcotic analgesics, as well as sibazone and ketamine, are currently used.
Epidural analgesia provides long-term and highly effective pain relief from the onset of labor until the baby is born, but can cause serious complications if careful monitoring and special preventive measures are not taken. The negative attitude towards this method is due to the fact that some doctors do not possess the technique or the necessary knowledge to apply it. Correctly performed epidural analgesia with sufficient capture of all segments can reduce pressure on the perineum and prevent it from tearing. For a mother, the most attractive aspect of epidural analgesia is that she remains conscious, can actively participate in the birth process and communicate with her baby immediately.
If necessary, during childbirth, a cesarean section is performed; it can be performed under the same epidural anesthesia without additional anesthesia. The same applies to manual examination of the uterus after childbirth, suturing of injuries of the perineum.
During analgesia during labor, the anesthetic is injected into the epidural space, followed by blockade of the subdural nerves in the segments with TX-LI.
Of the large group of local anesthetics in pregnant women, lidocaine is the most widely used, since bupivakine has a pronounced cardiotoxic effect, and novocaine has a neurotoxic effect. Lidocaine easily penetrates the placental barrier, the addition of epinephrine to the anesthetic solution significantly reduces the concentration of the anesthetic in the fetal blood.
Lidocaine is metabolized in the liver, the rate of its detoxification depends on hepatic blood flow, hepatocyte function and the degree of drug affinity for blood proteins. These factors can explain why, with prolonged infusions of the drug in pregnant women with preeclampsia, when liver functions are impaired, the drug often accumulates, which subsequently manifests itself as neuro- and cardiotoxicity in relation to the mother and the fetus.
When conducting epidural analgesia, a confidential relationship between the anesthesiologist and the patient is necessary, including a soothing conversation, as well as an examination of the lumbar region. The essence of the procedure must be explained to the pregnant woman in terms accessible to her and her consent must be obtained.
Preliminary preparation of equipment for monitoring, taking into account all possible complications, is mandatory. For this purpose, a peripheral or central vein should be catheterized in order to inject 500-1000 ml of crystalloid solutions before the onset of regional blockade. In women who are in the period of labor, the infusion solution should contain glucose, which should not be administered with the onset of the second stage of labor.
Puncture of the epidural and subdural space can be performed with the woman on her side or sitting. The position on the left side avoids the aortocaval compression syndrome and postural reactions after the administration of the test dose. Many anesthesiologists use the sitting position for puncture, since in this position the midline of the back is easier to identify, which is often difficult due to edema of the subcutaneous tissue of the lumbar region and sacrum. Another advantage of performing a puncture in a sitting position is the easier flow of cerebrospinal fluid. This is especially useful when using small bore needles.
The back is treated with an antiseptic solution, the excess of which is removed. The puncture site is covered with sterile linen. For puncture, the space between L3-L4, or between L2-L3 in the midline of the back can be used.
After local infiltration anesthesia, the skin is pierced with a thick needle to facilitate subsequent insertion of the epidural needle. The epidural needle is slowly advanced into the interspinous ligament. A 5 ml syringe is attached to it, in which there is an air bubble. Pressing lightly on the plunger to feel resistance, slowly advance the needle. When the latter passes the yellow ligament, resistance increases. After the needle passes through the ligamentum flavum, a sharp loss of resistance will be felt - the needle has entered the epidural space.
After the needle enters the epidural space, disconnect the syringe and make sure that there is no discharge of blood or cerebrospinal fluid from it. For epidural analgesia, the loss of resistance test is most useful for locating the needle lumen.
Other methods common in general surgical practice (“drop absorption”, etc.) are less suitable in pregnant women in the third trimester, since women have a significant increase in pressure in the epidural space, which often becomes positive.
This is due to an increase in intra-abdominal pressure and compression of the main veins. Therefore, when introducing a solution, some effort is often required; and sometimes even a reverse flow is noted, which in general surgical practice is usually regarded as an incorrect identification of the epidural space.
As a result of the influence of these factors in pregnant women, the risk of anesthetic getting into the subdural space or into the lumen of the vessel increases. In the first case, a total spinal block occurs, as evidenced by deep arterial hypotension, bradycardia, loss of consciousness and protective reflexes, wide pupils and respiratory arrest. This complication occurs when a dose of local anesthetic intended for epidural analgesia is inadvertently administered, i.e., too large.
The manifestation of cardio and neurotoxicity of local anesthetics is more often observed with intravascular ingress of injected solutions: convulsions, arterial hypotension, arrhythmias up to ventricular fibrillation occur.
Before placing an epidural catheter, you must inject 3 ml of local anesthetic. This small volume of fluid pushes the dura away from the catheter. Then you should advance the catheter about 3 cm behind the needle and remove the last. In this case, the catheter remains in place. Do not advance the catheter more than 3 cm to avoid increasing the risk of a monolateral block. It is contraindicated to change the position of the catheter at the time of withdrawal of the needle, since the latter can damage the catheter.
The distribution of local anesthetic solutions in the subarachnoid space is influenced by many different factors. In our opinion, the following factors are of greatest clinical importance.
An increase in intra-abdominal pressure almost always leads to greater diffusion of the local anesthetic solution during subdural anesthesia. This is due to the expansion of the venous plexuses, due to which the volume of the subarachnoid space decreases, especially in the syndrome of aortocaval compression. Most often this can be observed with multiple pregnancies, polyhydramnios, large fetuses, etc.
Anatomical changes in the spinal column. Scoliosis has no significant effect on the course of subdural anesthesia. Kyphosis in full-term pregnancy can alter the spread of the local anesthetic solution. In non-pregnant women, in the supine position, the lower S-curve of the spine flattens out to facilitate cranial spread of the solution. In pregnant women in the third trimester, this bend may, on the contrary, increase, and then most of the injected solution accumulates below the injection site.
CSF pressure and volume. CSF is produced by the venous plexus of the lateral ventricles at a rate of about 0.35 ml / min (500 ml per day) and is absorbed by the venous system of the meninges. The circulation of cerebrospinal fluid in the subarachnoid space is very slow, so it does not have a tangible effect on the spread of local anesthetic solutions. The volume of cerebrospinal fluid is about 150 ml, half of this amount is in the cranial cavity. The remaining 75 ml fill the subarachnoid space of the spinal cord, and a solution of local anesthetics can be distributed in this volume during subdural anesthesia. Clinical practice shows that usually anesthetics are distributed in a much smaller volume. In full-term pregnancy, the volume of cerebrospinal fluid in the thoracic and lumbar regions decreases due to an increase in intra-abdominal pressure and an increased venous volume in the epidural space. Due to this, both in the epidural and in the subdural spaces, the local anesthetic solution spreads much wider, and therefore, with the same amount of local anesthetic solution injected as in non-pregnant women, the area of the anesthesia spread may be much larger than desired.
At full-term pregnancy, cerebrospinal fluid pressure is normal. Sharp and sudden, but short-term rises in cerebrospinal fluid pressure, which occur during contractions and attempts, do not change the distribution of local anesthetic solutions in the subarachnoid space.
The nature of local anesthetic solutions is the main factor determining their distribution in the subarachnoid space. The most important are four main indicators: the specific gravity, the relative density of the local anesthetic solution in relation to the cerebrospinal fluid, the volume of the solution, and the concentration of the anesthetic in the solution. Hypertonic solutions are preferred because the use of hypotonic lidocaine solutions reduces the duration of anesthesia, making it unsuitable for many operations. The successful implementation of subdural anesthesia with hypotonic solutions is only possible if very powerful local anesthetics are used.
Anxiety, fear, emotional characteristics of the patient may require additional administration of sedatives. Sometimes these funds are used to eliminate the "effect of the presence of the patient." We believe it is best not to use sedatives until the baby is born. If, after removing the fetus, such a need persists or arises, then one should not strive for deep inhibition with sedatives in order to improve the quality of anesthesia. Much more effective is the additional introduction of solutions of local anesthetics into the catheter installed in the epidural space.
For almost fifteen years in obstetric practice, combined subdural-epidural anesthesia and analgesia have been used. The epidural space is punctured with a conventional epidural needle, through which the needle is then inserted to puncture the subdural space. After removal of the subdural needle, the epidural space is catheterized. The main application of the method is the intraspinal administration of narcotic analgesics for effective pain relief with the subsequent use of continuous infusional epidural analgesia from the end of the first stage of labor.
Epidural analgesia in the first stage of labor
Continuous epidural infusion analgesia (PEIA) is a rational and fairly simple method that provides long-term and safe pain relief during labor.
After we are convinced of the correctness of the epidural blockade, 0.5% lidocaine solution should be continuously infused into the epidural space at an initial rate of 10 ml / hour. Subsequently, the feed rate is adjusted depending on the reaction of the woman in labor.
The method is indicated for pain relief of contractions for 1.5-2 hours or more. It provides a number of advantages that cannot be achieved with fractional administration of anesthetics. When the drug is administered in fractional, bolus portions, it is difficult to completely eliminate the painful sensations of the mother that appear with increased frequency of contractions. When using PEIA, the need for local anesthetics is reduced by one third, due to which the development of a motor block is practically excluded. This high analgesic effect, combined with a reduction in the amount of anesthetic, is associated with the phenomenon of anticipatory analgesia.
Against the background of reliable analgesia, the mother remains quite active, the likelihood of various complications decreases. With a constant level of analgesia, tachyphylaxis occurs less often, which is usually observed with repeated injections of the drug. The state of hemodynamics is more stable, which is achieved by a uniform sympathetic blockade, which, with fractional injections of the drug, changes with each subsequent injection. Cardio- and neurotoxic reactions are minimized because anesthetics are administered at a very slow rate.
In the event that there is a migration of the catheter into the vessel, this will be manifested by the resumption of pain syndrome, and sometimes this complication is manifested by convulsions, severe arterial hypotension or arrhythmia.
Migration of the catheter into the subarachnoid space during epidural analgesia during labor is extremely rare. But even if this happened, then in the conditions of PIAI there will not be a life-threatening total spinal block, since the complication will manifest itself as a gradually increasing motor blockade of the lower extremities.
The greater safety of the method does not relieve the doctor of the obligation to ensure reliable monitoring during childbirth and does not at all provide him with the opportunity to leave the woman in labor alone during even the most calm course of the anesthesia process.
A label must be affixed to the drug dosing device indicating that the drugs are being administered epidurally, and the rate of administration must be accurately indicated.
Delivery room staff may confuse epidural lines with intravenous lines. This is especially dangerous in settings where dosing devices are also used to infuse oxytocin.
When performing PEIA, it should be remembered that large volumes of low concentration solutions spread over a larger number of segments (dermatomes) than small volumes of concentrated solutions. For example: 0.5% lidocaine solution at an infusion rate of 44 ml / hour applies to 16 dermatomes (220 mg), if 1% lidocaine solution is used at half the rate (22 ml / hour), then the same 220 mg applies only to 10 dermatomes.
Understanding the mechanism of the onset of pain in the first stage of labor, one should, of course, prefer low concentration solutions. Although high concentrations of anesthetic provide a stronger block, it is best to start with low concentration solutions, and if the depth of analgesia is insufficient, the doctor can deepen the block at any time by using a solution of a higher concentration.
In most cases, with an insufficiently deep level of analgesia, you can simply slightly increase the infusion rate, after making sure that the catheter has not migrated into the lumen of the vessel.
With the onset of the second stage of labor, analgesia must be continued, since the termination of the infusion in this period causes very severe pain.
Epidural analgesia in the second stage of labor
For anesthesia in the second stage of labor, the continuation of PEIA, which was started in the first stage of labor, is ideal. If it has not been used, it is necessary to carry out the same measures as at the beginning of epidural analgesia for the first stage of labor. However, preventive bolus intravenous fluid administration should be increased to 1000-1500 ml, which is due to an increase in the dose of local anesthetic for pain relief of the second stage of labor and, accordingly, a greater risk of arterial hypotension.
First, the same 3-4 ml is injected. solution of local anesthetic as a test dose. If after 5 minutes there are no signs of intravascular and subdural injection of the drug, then 10-15 ml is injected. solution, and the rate of introduction should not exceed 5 ml for 30 s.
Blood pressure must be measured every 2 minutes during the first 15 minutes after injection. Subsequently, blood pressure is monitored every 5 minutes until the onset of sensitivity blockade and hemodynamic stabilization.
If epidural analgesia is used only from the moment of establishing regular contractions, then it is preferable to start it when the cervix is dilated more than 5 cm. This avoids the negative effect of epidural analgesia on the process of childbirth.
If in the second stage of labor PEIA continues, started in the first period, then the concentration of the solution must be increased to 1.5-2%. Abrupt cessation of PEIA in the second stage of labor often results in very severe pain. As a physiological reaction to pain syndrome, which is described above, anxiety, fear, fear, and sometimes even anger arise.
The advantages of continuing PEIA in the second stage of labor are a weak motor block and the ability to subsequently control attempts. The duration of the second stage of labor, as a rule, does not change. Continuous injection of anesthetic into the epidural space excludes a sharp change in hemodynamics, which can occur with fractional administration of the drug. Adequate perineal anesthesia is often required immediately and immediately after birth. In most women, it persists for 15-20 minutes after stopping the lidocaine infusion. If the anesthesia of the perineum is insufficient, then 10-15 ml of a 1.5% lidocaine solution is additionally injected.
Complications of PEIA in childbirth
The most likely complications can be classified as follows.
1. Insufficient blockade of pain sensitivity: the most important danger of this complication is the disappointment of the woman in labor in the method and in the anesthesia team. Unfortunately, even in the most experienced hands, this complication occurs in 5-10% of cases. The most common cause of insufficient blockage is a catheter that is too far advanced or a spinal disorder that limits the spread of the anesthetic. If the catheter is advanced no more than 3-4 cm beyond the lumen of the needle, this complication is less common. Most often, the catheter is difficult to advance when it is not in the epidural space. Forcible advancement of the catheter is unacceptable, as this can cause damage to the sharp edges of the needle or migration into the lumen of the vessel. The best way out in such a situation is to repeat the puncture and the whole procedure in another intervertebral space.
2. The emergence of a unilateral block is usually due to the fact that the catheter is located laterally. Less commonly, this indicates anatomical abnormalities in the epidural space. In this case, the woman in labor must be turned to the side on which there is no effect, the catheter must be pulled up by 1-2 cm. In this position, the woman in labor is injected with the next dose. If this does not help, it is necessary to repeat the puncture.
3. Maternal hypotension is the most common side effect of a successful epidural block. Since with a decrease in blood pressure the possibilities of autoregulation of uteroplacental blood flow are sufficiently preserved, one should not panic if this complication occurs. However, the maintenance of normal placental blood flow during arterial hypotension due to compensatory mechanisms can easily be disrupted, especially in pregnant women with preeclampsia, diabetes mellitus and uteroplacental insufficiency. For this reason, in the delivery room, constant monitoring of the condition of the fetus is necessary in order to assess how it reacts to the maternal hypotension. To correct arterial hypotension caused by an epidural block, it is usually sufficient to increase the rate of intravenous infusion.
4. Intravascular injection of anesthetic can manifest itself as a slow development of toxic effects. Timely noticed, this complication quickly disappears when the catheter is where it needs to be - in the epidural space.
5. Accidental puncture of the dura mater with a subdural catheter can occur with the use of sharp needles of small diameter, when habitual landmarks of loss of resistance decrease, and the needle can easily pass the dura mater. About half of these patients develop post-puncture pain syndrome, including headache. The incidence of this complication, even in experienced hands, is 0.5-1%. Epidural analgesia sometimes contributes to the onset of hyperthermia during labor. This effect is associated with sympathetic blockade and disruption of normal thermoregulation, and is not too dangerous.
Absolute contraindications for epidural analgesia during labor are:
1) lack of qualified anesthetic personnel and equipment for round-the-clock observation, both during childbirth and in the postpartum period;
2) infectious inflammation at the puncture site, as well as septicemia;
3) coagulopathy, laboratory confirmed or expected due to the nature of the existing pathology;
4) anatomical abnormalities: splitting of the arches of the vertebrae or myelomeningocele, pronounced kyphoscoliosis (caudal access is possible), congenital malformations of the vascular system of the spine.
Relative contraindications:
1) anatomical or technical difficulties in performing puncture or catheterization of the epidural space (obesity, curvature of the spine),
2) lack of consciousness or insanity of the patient;
3) uncorrected hypovolemia;
4) neurological diseases, for example, multiple sclerosis;
5) heart disease in the absence of full hemodynamic monitoring.
Spinal methods of analgesia with narcotic analgesics
Epidural analgesia with concentrated solutions of local anesthetics can sometimes increase the duration of the first and second stages of labor, and then it becomes necessary to use oxytocin or in operative delivery. These shortcomings have stimulated physicians to search for other pharmacological agents that can induce a sufficient level of analgesia when administered epidural or subdural.
For the first time, evidence that the subarachnoid administration of narcotic analgesics causes analgesia in humans appeared in the late 70s. In the 1980s, the use of opioids for epidural and subdural anesthesia began to spread in obstetric anesthesiology. Both methods provide good analgesia with low doses of drugs and have less dangerous side effects compared to autoanalgesia with intravenous narcotic analgesics.
The requirements for the use of narcotic analgesics for the epidural and subdural routes of administration are very simple: long-term analgesia should be provided with a small dose of the drug and be accompanied by minimal resorptive effects.
Small doses of narcotic drugs, when administered epidurally or subdurally, can provide adequate analgesia for the mother in labor with minimal side effects, both for the mother and the newborn. With intravenous or intramuscular administration of large doses of narcotic analgesics, these effects are always significantly greater.
The standard technique for epidural analgesia during labor involves the administration of a bolus dose of local anesthetics followed by continuous infusion. The first reports of satisfactory analgesia in labor with epidural morphine instead of local anesthetics have raised skepticism. Subsequent studies have shown that the use of small doses of morphine for epidural anesthesia (2.0-5.0 mg) does not provide satisfactory pain relief during labor. Morphine in doses of 7-8 mg causes prolonged analgesia, which can last up to 24 hours. The main disadvantage is the slow development of analgesia (from 30 to 90 minutes) and pronounced side effects. Most women in labor report insufficient analgesia, accompanied by nausea, vomiting and itching. It is also very important that the fetus is at risk of exposure to high doses of morphine, which crosses the placental barrier well.
The use of fentanyl (150-200 μg) for epidural analgesia has made it possible to achieve more significant success. Long-term infusions into the epidural space of low doses of fentanyl (2.5 μg / h) provide effective postoperative analgesia in patients with a general surgical profile, which can also be used in women in labor. Epidural administration of 50-200 μg of fentanyl causes a rapid (after 5-10 minutes) onset of analgesia, but, unfortunately, the effect does not last long (1-2 hours). Fast and long-term pain relief with minimal side effects can be achieved with a combination of low doses of morphine and fentanyl. Such analgesia occurs a few minutes after the administration of drugs and lasts 4-5 hours. Usually this is enough for childbirth. Due to a sharp decrease in the doses of drugs administered in such a combination, side effects and complications of each of them are minimized. The combination of epidurals of narcotic analgesics and local anesthetics has been excellent. The addition of fentanyl (50-150 mcg) improves the quality of analgesia compared to using local anesthetic alone. Newborn Apgar scores, cord blood gas measurements, and neurologic status remain normal.
Of particular interest is the use of narcotic analgesics of the agonist-antagonist type. For example, stadol (butarfanol) is an opioid K receptor agonist and an M receptor antagonist. Therefore, it has not only analgesic properties, but also has a sedative and antitussive effect, increases blood pressure, etc. blockade of motor nerves.
The only side effect observed with this is somnolence, which increases with dose, but does not require any treatment. Fetal hangar scores, cord blood gases and neurologic tests remain normal. Thus, stodol-type antagonist agonists can be used in conjunction with local anesthetics and their effect is comparable to that of morphine or promedol.
The first drug that began the use of narcotic analgesics for subdural pain analgesia was the same morphine. The women in labor did not feel pain, but they “felt” the contractions and, therefore, the blockade with narcotic analgesics was not as absolute as the blockade with local anesthetics. This can be recommended for those women who need pain relief while actively participating in childbirth. Although subdural analgesia with morphine gives good results in the first stage of labor, it is completely ineffective in the second. But to achieve pain relief in the first period, only 0.5 mg of morphine is enough.
Since the drug is injected directly into the cerebrospinal fluid, morphine allows for sufficiently effective analgesia at significantly lower doses than with epidural administration. High concentrations in the cerebrospinal fluid with subdural analgesia can be achieved with the introduction of even 0.25 mg of morphine. The exact dosage has not yet been determined, but doses in the range of 0.5-1.5 mg of morphine with subdural administration are, in our opinion, optimal.
Although subdural analgesia with morphine provides adequate pain relief during labor, the method is not without its drawbacks.
Firstly, such use of the drug does not provide the controllability and flexibility that epidural analgesia with local anesthetics in the form of (PEIA) gives us. If surgery is necessary during labor, such as forceps or episiotomy, the addition of local anesthetics is required. Subdural analgesia with narcotic analgesics provides analgesia for visceral pain, that is, only in the first stage of labor.
Secondly, the onset of analgesia occurs only after 45-60 minutes, therefore, the doctor must do subdural analgesia with morphine before the cervix dilates by 3-4 cm and the contractions are relatively painless. The use of subdural anesthesia and analgesia with large doses of morphine can be accompanied by nausea, vomiting, urinary retention, discomfort, and respiratory depression. This develops due to the general resorptive action.
The course of labor and the degree of cervical dilatation are practically unchanged with epidural or subdural analgesia with morphine (1-2 mg). However, epidural anesthesia with fentanyl or stadol in combination with local anesthetic solutions can significantly shorten the first stage of labor.
The use of narcotic analgesics for subdural analgesia may find its place in cases where the cardiovascular and neuromuscular effects of local anesthetics are undesirable or even dangerous. For women in labor with concomitant cardiac pathology, the likelihood of complications increases at moments of sharp increase or decrease in total vascular resistance. This can be avoided by using narcotic analgesics for epidural or subdural analgesia, while excluding the introduction of local anesthetics. The use of subdural analgesia with morphine may be beneficial in hypertensive pregnant women. For patients with aortic stenosis, tetrad of Fallot, Eisenmenger's syndrome, coarctation of the aorta, subdural analgesia with the use of narcotic analgesics is the method of choice for pain relief in labor.
Effective analgesia, which is carried out with low doses of narcotic analgesics, eliminates not only the painful stress factors of the mother, but also reduces the risk of complications in the fetus. Narcotic analgesics cross the placenta very quickly, which is another factor limiting their dose. Fentanyl (75 mcg), injected into the epidural space, crosses the placental barrier, but this does not manifest as signs of drug-induced depression in the newborn.
The most dangerous side effect of this method is respiratory depression. Clinical experience shows that the period of greatest risk of developing this complication is between 4 and 8 hours after the start of epidural analgesia, when the drug is distributed by CSF to the centers of respiratory regulation.
Within 2 hours, drugs should not be administered orally, intramuscularly, intravenously or subcutaneously, unless they are prescribed by an anesthesiologist. Respiratory monitoring (respiration rate, pulse oximetry) should be carried out, and if it is absent, the respiration rate should be checked every 30 minutes during the first 12 hours, then every hour until 24 hours have elapsed since the administration of the narcotic analgesic. A heparin-sealed venous catheter should be kept. The patient should have instruments, devices and medicines necessary for respiratory resuscitation (an intubation set with a laryngoscope, etc., naloxone in ampoules, etc.).
Complications may include nausea, vomiting, itching, and urinary retention. To treat these complications, you can use:
1) naloxone 0.25 ml (0.1 mg) every 15 minutes. i / v three times,
2) if there is no effect within 45 minutes, a continuous intravenous injection of naloxone 0.2 mg / hour in a 0.4% solution should be started. If the situation does not improve within 60 minutes, increase the infusion rate to 0.4 mg / hour.
When pain resumes, the question of additional anesthesia is decided only by the anesthesiologist.
3) cerucal 10 mg IV every 2 hours to eliminate nausea.
The most common side effect of epidural or subdural analgesia with narcotic analgesics is pruritus. The mechanism of itching is not completely clear, but apparently this is not associated with the release of histamine. Itching is dose-dependent and increases with an increase in the concentration of the narcotic analgesic in the cerebrospinal fluid. Most often it appears with the use of morphine, less often with the use of fentanyl or promedol. Pyritramide (dipidolor) can be used for epidural anesthesia. Intravenous administration of naloxone (0.1–0.2 mg) is very effective in eliminating this side effect.
Delayed urination is a very painful side effect, but for most women this problem is easily resolved with a bladder catheter.
Thus, epidural and subdural analgesia with narcotic analgesics in obstetrics has proven itself very well. However, it should be remembered that these methods, which have many advantages, can be used with a good understanding of the essence of the method, the clinical pharmacology of the drugs used and the clinical physiology of functional changes occurring in the body. Adequate continuous monitoring of the condition of women in labor is necessary, especially when the doctor is still mastering this method. In the hands of an experienced specialist, any method looks like a salutary miracle, whatever dangers lurk in the essence of the method. But the best method can be discredited by inept and illiterate followers.
Rice. 2. The dependence of the use of methods of labor pain relief on the intensity of pain and the degree of cervical dilatation.
Based on the above information, we propose the following scheme for the use of methods of pain relief in childbirth (Fig. 2).
Pain relief for violations of the contractile function of the uterus
Currently, the problem of uterine contractile activity is the most urgent in modern obstetrics, because a significant part of the pathological conditions that arise during pregnancy and childbirth are associated with impaired motor function of the uterus. Previous studies indicate the undoubted role of neurohumoral regulation of the functional state of the uterus. The hypothalamus and the structures of the limbic complex, primarily the amygdala and cortical formations in the temporal lobes of the cerebral hemispheres, are of leading importance in this process. The placenta, ovaries and other endocrine glands also have a regulatory effect on the motor function of the uterus. The uterus, as an effector, plays a certain role in the nature of labor and, as a feedback, influences other competent systems. The role of the central correcting link belongs to the amygdala and hypothalamus, which ensure the sexual functions of a woman.
The act of childbirth takes place in the presence of a formed generic dominant, which unites both the higher nerve centers and the executive organs into a single dynamic system. A special role in the contractile activity of the uterus is assigned to chemoreceptors, which include choline and adrenergic receptors. Recently, a close relationship has been found between the hormonal activity of the fetus and the placenta, which gives reason to talk about the so-called feto-placental unit or feto-placental system, which plays an important role in the regulation of the contractile activity of the uterus.
Most authors point to the role of estrogens, which contribute to an increase in the synthesis of proteins of the actomyosin complex, an increase in energy metabolism, an increase in the activity of enzymatic reactions, and the maturation of the cervix.
Since the onset of labor, the contractile function of the uterus is closely related to the intensity of tissue metabolism of the myometrium, the level of energy metabolism. In the dynamics of childbirth, metabolic processes reach the highest level, which is associated with a significant expenditure of energy. The proportion of anaerobic glycolysis and metabolic acidosis increases.
In addition to enzyme systems, hormones, mediators, and biologically active compounds are involved in the regulation of labor.
In addition to the regulation of labor, all these factors are involved in the regulation of blood circulation, change the permeability of cell membranes, the hemostasis system, etc.
A violation at one of these stages undoubtedly leads to a violation of labor. Under the influence of labor, especially those that are protracted, persistent changes occur in many metabolic processes, which lead to a rapid depletion of the body's energy resources.
In addition, the weakness of labor leads to a violation of the neuropsychic state of a woman, an increase in the frequency of surgical interventions, the frequency of fetal and newborn asphyxia. Perinatal mortality is sharply increasing, ranging from 10.3 to 37.5%. Maternal mortality in this pathology is 0.7-2.8%.
Hypertensive disorders of uterine contractility are less common than hypotonic. The essence of this pathology, according to I.S. Sidorova (1997), is a change in the functional balance of the autonomic nervous system with the dominance of the influence of the parasympathetic part, hyperproduction of acetylcholine, which causes contraction of the circular muscles of the uterus. Often there is a lack of synchronicity of contractions and relaxation of various parts of the uterus. A special risk in this pathology is represented by such formidable complications as placental abruption, uterine rupture, bleeding caused by combined abnormalities of uterine contractility and impaired hemostasis.
The following forms of uterine dysfunction are distinguished: pathological preliminary period, discoordination of labor, rapid labor, segmental dystocia, tetanus of the uterus. A pathological preliminary period is observed in women with endocrine disorders, obesity, vegetative neuroses, neurocirculatory vascular dystonia, in the presence of fear of childbirth, in pregnant women with a burdened obstetric history, complicated by the course of this pregnancy, in primiparous women, etc.
The pathological preliminary period is a kind of protective reaction of the pregnant woman's body, aimed at the development of contractions, in the absence of sufficient readiness for childbirth, and, above all, of the uterus. This reaction is realized through an increase in the contractile activity of the uterus, usually discoordinated, aimed at ripening the cervix and opening it.
The pathological preliminary period is characterized by painful irregular contractions, pain in the lower abdomen, in the sacrum and lower back, lasting more than 6 hours, sometimes several days, disrupting the daily rhythm of sleep and wakefulness, causing the woman's fatigue and signs of fetal suffering. The main etiological moments leading to the development of clinical manifestations of the pathological preliminary period are functional shifts in the central nervous system, which has been proven by encephalographic studies. This is also evidenced by vegetative and endocrine disorders.
It should be borne in mind that with a long preliminary period, energy consumption increases, which leads to a rapid depletion of energy resources and the development of weakness of the birth forces. If this is accompanied by prenatal rupture of amniotic fluid against the background of an "immature" cervix, it is necessary to assume the presence of deeper disturbances in the neuroendocrine and myogenic regulation of uterine contractile activity.
Treatment of the pathological preliminary period should begin with central regulation by introducing sibazon, seduxen, diazepam intramuscularly at a dose of 10 mg or intravenously in 20 ml of isotonic sodium chloride solution. With a prolonged (10-12 hours) preliminary, when, after the introduction of seduxen, irregular pains continue to bother the pregnant woman and she is tired, it is necessary to inject 10-20 ml of a 20% solution of GHB. At the same time, treatment is indicated, aimed at the ripening of the cervix.
With an unprepared cervix, it is necessary to use estrogens (20,000 IU each), PG E2 preparations (protenon, diproston, prepedil-gel), antispasmodics (baralgin, no-shpa, etc.). It is not recommended to use drugs with a reducing effect for any kind of discoordination of labor.
Adequate timely treatment of discoordination of labor, as a rule, contributes to its normalization. The choice of appropriate therapy and prognosis of childbirth is carried out taking into account the age of women, obstetric and somatic history, the course of pregnancy, an objective assessment of the condition of the fetus.
With discoordination of labor activity, a pathogenetically justified method of therapy is the conduct of long-term epidural anesthesia.
Discoordination of labor activity can also be caused by the wrong tactics of labor management, in particular, repeated, haphazard use of oxytotic drugs. In this case, an overdose of these drugs can lead to hypoxia and even fetal death.
A fairly common anomaly of labor is weakness, which is diagnosed on the basis of insufficient activity of the uterus, a decrease in the rate of smoothing of the cervix and disclosure of the uterine pharynx, prolonged standing of the presenting part of the fetus at the entrance to the small pelvis and its slow advance in accordance with the size of the pelvis. At the same time, the duration of childbirth increases, fatigue of the woman in labor is observed.
Before prescribing rhodostimulating drugs in the presence of fatigue during childbirth, it is necessary to give the woman rest in the form of pharmacological sleep. The correct and timely provision of rest leads to the restoration of the disturbed functions of the central nervous system. In these situations, rest helps to restore normal metabolism in the uterus.
In order to provide rest for women in labor, morphine, pantopon, promedol are used in combination with diphenhydramine, sibazon, etc. This scheme can be carried out by an obstetrician-gynecologist (midwife) without an anesthesiologist.
In the presence of an anesthesiologist in case of fatigue during childbirth, the steroid anesthetic Viadril (preion, prosuren, hydroxydione) is successfully used. Being similar to the natural metabolites of the human body, viadril has low toxicity and a wide range of therapeutic action. In narcotic doses, it induces physiological sleep. Among the positive qualities of viadril, one should especially emphasize its antispasmodic and anticholinesterase effect. Of the side effects, breathing disorders, the appearance of phlebitis at the injection site should be noted.
It is necessary to use the following technique. For 15-20 minutes, premedication is carried out by introducing 20 mg of promedol, 25 mg of diprazine and 1 mg of metacin. To exclude the irritating effect of viadril on the intima of a venous vessel, a so-called "sealed" solution is introduced. To do this, 15 ml of a 2.5% solution of viadril, preheated to 35-36 ° C, is collected in a twenty-gram syringe. Then a vein is punctured and 5 ml of blood is drawn into a syringe with viadril (a total of 20 ml of solution). The blood, mixing with the viadril, is a kind of buffer for it, when the degree of alkalinity of the solution decreases, and the protein components of the blood reduce the irritating effect of the viadril on the intima of the veins (the pH of the resulting solution is 8.6). Before and after the introduction of viadril at a dose of 8-10 mg / kg. weight, 5 ml of 0.25% novocaine solution is injected intravenously. When using this technique, anesthesia proceeds in stages I-II.
Another way of treating fatigue during labor is the use of GHBa - gamma-aminobutyric acid. Narcotic action of GHB of cortical origin. The drug has a pronounced hypothermic effect, does not disrupt energy metabolism, the processes of phosphorylation of respiration. The antihypoxant effect of GHB is realized by reducing the degree of acidosis, the level of lactate, and normalizing the hormones of the pituitary-adrenal system. The drug has a sedative effect, enhancing the effect of analgesics. However, with its introduction, motor excitement is possible in the form of convulsive twitching of the limbs, impaired respiratory function. In this regard, it is recommended to inject GHB slowly (1-2 ml per minute) after preliminary administration of sibazone (5-10 mg) at the rate of 40-60 mg / kg of the mother's weight.
Since 1971, L.S.Persianinov, N.N. Rasstrigin and E.M. Kastrubin introduced the method of electroanalgesia into obstetric practice. It was found that its use allows achieving a stable vegetative balance, avoiding allergic reactions that may occur when using pharmacological drugs (neuroleptics, ataractics, analgesics).
In contrast to pharmacological drugs, the use of a pulsed current allows one to obtain the so-called "fixed" stage of therapeutic analgesia, which makes it possible during the labor act to maintain consciousness, verbal contact with the woman in labor without signs of her excitement and transition to the surgical stage of anesthesia.
For therapeutic analgesia in case of fatigue in childbirth, domestic devices "Electronarkon-1", "Lenar" are used. Before applying the electrodes, 15 minutes before the onset of exposure to a pulsed current, premedication is carried out with 1 ml of a 2% solution (20 mg), 1 ml of a 2.5% solution of diprazine (25 mg), 1 ml of a 0.1% solution of metacin (1 mg). Before applying the electrodes, the skin of the forehead and neck is wiped with alcohol. Gauze napkins in 8-10 layers (3x3 cm) soaked in 0.9% sodium chloride solution are placed under the electrodes. The cathode (negatively charged electrode) is placed on the forehead, the anode (positively charged electrode) on the area of the mastoid processes. After fixing the electrodes, the device is connected. The pulse repetition rate is set within 750 Hz, the pulse duration is 0.5 ms. Then the impulse current slowly increases up to threshold sensations (tingling sensation, creeping "creeps") in the area of the electrodes. Every 15-20 minutes it is necessary to increase the average current value by rotating the "pulse current" knob or by increasing the pulse repetition rate to 1000-1500 Hz. The average value of the current strength for this pathology is 0.8-1.2 mA with a session duration of 1.5-2 hours.
It should be noted that in the presence of hypertensive syndrome, the introduction of viadril or GHB is recommended. On the contrary, in women in labor with hypotension, tachycardia, a tendency to thrombosis, in the presence of a so-called "full" stomach, the use of therapeutic electroanalgesia is the main method of therapy.
In the presence of such risk factors as a burdened obstetric and gynecological history (infertility, induced pregnancy, etc.), extragenital pathology, gestosis, chronic fetal hypoxia, it is advisable to choose the method of delivery by cesarean section without the above therapy.
This is due to the fact that all the factors described are dangerous to the life of a woman and her fetus with conservative management of childbirth. In addition, with discoordination of labor, complications such as rupture of the uterus, amniotic fluid embolism, placental abruption and, as a consequence, hypotonic and coagulopathic bleeding may occur.
It must be remembered that with this pathology and the presence of a hypertensive syndrome, ganglion blockers that inhibit the secretion of catecholamines, leading not only to uterine hypotension, but also to the occurrence of ischemic damage to the fetal brain, cannot be used.
Control over the course of labor is carried out with constant medical supervision, cardiac monitoring of the cardiac activity of the fetus and the contractile activity of the uterus; it is necessary to maintain partograms. Childbirth with discoordination of labor should be carried out in the presence of an anesthesiologist for the timely provision of resuscitation assistance, especially in the case of using viadril, GHB. At the time of the birth of the child, a neonatologist who knows resuscitation methods must be in the delivery room.
Pathophysiological basis for the development of intrauterine fetal hypoxia
The leading role among the direct causes of perinatal morbidity and mortality belongs to fetal hypoxia. The importance of hypoxia in perinatal pathology is not limited to high rates of stillbirth. Hypoxic changes in the antenatal period often lead to severe lesions of the central nervous system in a newborn baby. According to the observations of a number of authors, many children who underwent intraoral hypoxia subsequently die from its consequences. The percentage of such children ranges from 12.8-26.0 of the total contingent.
A special group of perinatal pathology is represented by newborns with fetal growth retardation syndrome (FGRS) and low birth weight. Perinatal morbidity and mortality among this group is 5-8 times higher than in the general population. So, prematurely born children account for 60% of cases of stillbirth, 50-70% of neonatal and 48-66% of child mortality.
It is known that intrapartum hypoxia can be caused by various forms of obstetric complications and extragenital diseases.
The main factor in the development of a hypoxic state of the fetus is placental insufficiency. The latter manifests itself in the form of chronic or acute fetal hypoxia, which often manifests itself in a delay in its development. The frequency of detection of chronic placental insufficiency ranges from 8 to 33%, in 20-40% of cases it is the cause of perinatal morbidity and mortality. In case of placental insufficiency, the reserve capacity of the feto-placental system (FPS) as a whole and the fetus is significantly reduced. In this regard, the ability to develop adequate adaptive reactions in various stressful situations and extreme conditions during pregnancy and childbirth, during anesthesia, is impaired, especially when FGRP is combined with chronic or acute fetal hypoxia.
With pronounced FGR, especially developed against the background of gestosis, the severity of gestosis, as a rule, correlates with the severity of FGR and placental insufficiency. Moreover, according to a number of authors, fetal growth retardation may be due to both the pathology of the maternal organism and the fetus itself and the placenta. The level of perinatal pathology in women with low birth weight is influenced not only by maternal diseases leading to miscarriage, but also by long-term drug therapy for this pathology.
In the literature, you can find several classifications of the syndrome of placental insufficiency. Thus, Kulbi et al. (1969) distinguish between chronic (throughout pregnancy), subacute (developing immediately before the onset of childbirth) and acute placental insufficiency. Botella-Llusia (1980) considers it more rational to isolate chronic (during pregnancy) and acute (during labor) forms in the symptom complex of placental insufficiency. At the same time, placental insufficiency is more of a clinical than a pathophysiological or pathomorphological concept, since changes in the placenta are the result of various pathogenetic factors.
In the development of hypoxia, great importance is attached to violations of the uteroplacental circulation and blood flow velocity.
There are a number of factors on which adequate oxygen supply to the fetus depends. These include maternal, including extragenital diseases, smoking and alcohol abuse. Uterine factors include a decrease in uteroplacental blood flow due to late gestosis or concomitant extragenital diseases, impaired uterine contractile activity, and morphological changes in the spiral arteries. There are also placental factors directly, including inflammatory changes, heart attacks and thrombosis of the placenta, and fetal factors, which include Rh-conflict, malformations, etc.
Thus, fetal hypoxia is not an independent pathology, but is caused by a variety of clinical pathologies of a pregnant woman. Moreover, in the structure of perinatal mortality, fetal hypoxia takes the first place, the share of hypotrophy is from 5.7 to 30%.
Before presenting the pathogenesis of the development of fetal hypoxia, it is necessary to know in what conditions the fetus is in a normal physiological pregnancy. Previous studies have shown that the supply of oxygen to the fetus, even under physiological conditions, is reduced in comparison with the adult body. Moreover, the increased tolerance to oxygen deficiency in the fetus and newborn is explained by the presence of adaptive mechanisms developed at the stage of intrauterine development due to the action of the hypoxic factor in the embryonic period. It was found that at a gestational age of 22-23 weeks, the pH value from the umbilical cord vein (arterial blood) is 7.34 (0.04), from the umbilical cord artery (venous blood) - 7.33 (0.017). At the end of physiological pregnancy, the shift in the fetal blood pH towards the acidic reaction becomes greater, the arterial blood pH is 7.28 (0.97). There is an increase in the base deficit up to 11.05 (2.4 mmol / L of blood). Similar changes, i.e., the phenomenon of metabolic acidosis, were found in a pregnant woman.
It is known that the exchange of gases in the placenta is similar to gas exchange in the lungs. At the same time, fetal gas exchange is more dependent on the rate of uteroplacental blood flow than on the diffusion properties of the placenta. As a result of the peculiarities of the fetal circulation (the functioning of three arteriovenous shunts), almost all organs of the fetus receive mixed blood. The fetal liver is in the most favorable conditions, which is the only organ that receives almost pure arterial blood (oxygen saturation is about 80%). Sufficiently oxygenated blood also enters the coronary arteries and blood vessels that feed the brain (oxygen saturation - 68%), in the worst conditions are the lungs of the fetus, the lower body. However, these tissues do not suffer from a lack of oxygen under normal conditions of existence, as evidenced by the rate of oxygen absorption by the fetal tissues (4 ml of oxygen per minute per 1 kg of weight), which is equal to that of an adult. This is due to an increase in the minute volume of the fetal heart, which is 198 ml / kg at 70 ml / kg in adults. The heart rate increases by increasing the speed of blood flow. An important role in maintaining normal fetal homeostasis is played by the presence of fetal hemoglobin, anaerobic glycolysis, which is the most beneficial and economical, since it leads to the release of much less energy.
At the end of physiological pregnancy, due to the predominance of the anaerobic pathway of glycolysis, the content of lactate and pyruvate in the umbilical cord blood is 2 and 1.5 times higher than in the mother's blood. In childbirth, the intensity of glycolysis processes increases slightly, which indicates the absence of an increase in oxygen deficiency in the dynamics of labor. Of all energy and plastic materials, glucose is the main metabolic product. During physiological childbirth in newborns, in 46.7% of cases, the level of glucose in the umbilical cord blood is within the normal range (3.5-5.5 mmol / l), in 33.3% there is hyperglycemia, in 11.1% - hypoglycemia (level glucose 2.2 mmol / l).
In the fetus during the physiological course of pregnancy and childbirth, the presence of the so-called natural hypobiosis was revealed. This is evidenced by the anaerobic pathway of glucose cleavage according to the determination of LDH and MDH in the fetal umbilical cord blood, the presence of hypoglycemia (fluctuations in glucose from 2.1 to 3.4 mmol / L), metabolic acidosis, a decrease in the concentration of ACTH and cortisol to 22.5, respectively ( 0.8 pmol / l) and 849 (18.7 nmol / l) in cord blood and the level of hormones of the pituitary-thyroid system: T3 up to 1.56 (0.02 ng / ml), T4 up to 10.83 (0, 41 ng / ml) and TSH up to 2.13 (0.1 mIU / ml), the appearance of bradycardia in the fetus in the second stage of labor. Moderate hypoproteinemia is noted: protein - 48.7 (4.5 g / l), an increase in lactate in the umbilical cord blood by almost 1.4 times compared with the mother's blood data up to 4.9 (0.2 μmol / l). There is also a decrease in the level of glucose, potassium, sodium and calcium in comparison with the indicators in the umbilical cord blood. At the same time, with a high degree of functional readiness and structural differentiation of the endocrine apparatus, literature data indicate a decrease in its reactivity. If we take into account that at high concentrations of hormones, the processes of oxygen absorption are enhanced, the metabolism of proteins, fats and carbohydrates is accelerated, the synthesis and breakdown of lipids is stimulated, then it is in conditions of a reduced content of these hormones that more optimal conditions for the functioning of the vital functions of the body are created in the fetus. Moreover, this decrease, according to a number of authors, is of a protective and adaptive nature, ensuring the economical use of oxygen.
There is a high reliable correlation between the partial tension of oxygen in the mother's blood and the amniotic fluid (r = 0.734), between the saturation indicators of this substrate in the studied parameters (r = 0.439), a decrease in the dynamics of childbirth in the pH value of amniotic fluid from 7.258 (0.07) up to 7.049 (0.012), an increase in pCO2 from 42.7 (2.1) to 48.8 (2.2) mm Hg. Art. and a decrease in pO2 from 64.5 (4.0) to 47.5 (5.0 mm Hg).
In the early neonatal period, a rapid drop in glucose begins. In most newborns, even a significant decrease in its blood level does not entail clinical symptoms. A number of authors explain the appearance of hypoglycemia by insufficiency of the insular apparatus and the glycogen-forming function of the liver and muscles in newborns, or hyperinsulism. Other researchers have shown that newborns lack a compensatory response to the hypoxic factor in the form of hyperglycemia, explaining this by the immaturity of glycogenic function. That is, most authors explain hypoglycemia by the immaturity or imperfection of certain systems of the newborn. At the same time, hypoglycemia is characteristic of both a premature and healthy full-term newborn.
The concentration of urea, as the end product of protein metabolism, in umbilical cord blood is within the normal range (from 3.5 to 3.8 mmol / l). If we take into account that the synthesis of cellular protein is carried out by the tissues of the fetus mainly from amino acids and carbohydrates, then the products of its catabolism are nitrogen-containing substances (ammonia), some of which are resynthesized. The other part is excreted from the body in the form of urea and uric acid. Taking into account the normal parameters of urea, it can be assumed that in the process of uncomplicated pregnancy and childbirth there is a physiological relationship between anabolic and catabolic reactions of protein metabolism.
The most pronounced changes were found in the electrolyte balance of the blood. In the umbilical cord blood, hypernatremia, hyperkalemia are noted. At the same time, there is a directly proportional relationship between the concentration of Na + and K + in plasma and blood erythrocytes. Their level in plasma exceeds these indicators in blood erythrocytes, that is, there is a certain dependence of their cellular reserves in fetal erythrocytes. Similar changes in the biochemical parameters of the fetal blood were found in low birth weight children. The concentration of Ca + in the plasma of the umbilical cord blood is also relatively high compared to its concentration in the mother's blood. This is due to the accumulation of Ca + in the last months of pregnancy and an increase in the albumin-bound fraction. It can be assumed that a high concentration of electrolytes may be due to the existing acidosis and, as it were, a compensatory reaction of the fetus to acidotic changes in its body.
When analyzing the literature data, it was found that the fetus, with its normal existence, has a reduced reactivity, refractoriness and other vital systems of the fetus, in particular the pituitary-adrenal and thyroid systems. It has been established that these systems function from the earliest period of antenatal ontogenesis. However, by the time of birth, they remain qualitatively immature. There was also found a low phagocytic and lysozyme activity of properdin in blood serum of newborns, which is one of the factors of nonspecific protection. There is also a low interferon-synthesizing activity of leukocytes, which is two times lower than in adults.
With regard to thermoregulation of newborns, there is a complete readiness to carry out this function, on the other - its imperfection, immaturity, and insufficiency. At the moment of birth of the head and the whole body, as a rule, there is a lack of spontaneous movements, proprioceptive and exteroceptive reflexes, muscle atony and deep inhibition of the wakefulness function. The fetus does not respond to intense stimuli of the skin and proproceptive, visual, auditory and olfactory analyzers. This functional unresponsiveness to various intense external stimuli indicates a deep inhibition of the central nervous system of the fetus and can be simply qualified as a deep phase of slow wave or paradoxical sleep. The fetus at this moment is, as it were, in a state of deep anesthesia with respiratory arrest or resembles an animal in a state of hibernation.
In connection with the above, until recently, all changes in the body of the fetus were interpreted as a result of immaturity, imperfection of the vital functions of the body. However, the works of a number of researchers have shown that the fetus under physiological conditions of existence is characterized by refractoriness, hypo- or non-reactivity. It is precisely this nature of metabolic processes, according to their data, that is a peculiar form of fetal protection - this ancient protective mechanism of hypobiosis. This concept is confirmed by the works of N.I.Sirotin (1981), who showed that during hibernation, the reactivity of animals decreases, while their resistance increases. These include hyporeactivity, a decreased level of metabolic processes, a predominantly anaerobic pathway of glucose breakdown, hypoglycemia, acidosis, etc.
Hypoxic conditions of the body, often accompanying childbirth, serve as the basis for many diseases of the fetus and newborn. At the heart of hypoxic damage, first of all, is the restriction of oxygen delivery to tissues.
The existing classifications distinguish from 4 to 8 types of hypoxia and its various stages from latent to terminal. Most researchers distinguish between 4 types of hypoxia: hypoxic, hemic, circulatory and histotoxic. In recent years, it is planned to add a fifth type of hypoxia - tissue hypoxia arising from an increase in the affinity of hemoglobin for oxygen.
Hypoxic, circulatory, hemic hypoxia can occur primarily as a result of the pathological course of pregnancy, childbirth, or a disease of the fetus itself. Tissue hypoxia is a rare form and occurs secondarily as a consequence of other forms of oxygen deficiency.
There is another classification in which arterial-hypoxemic, ischemic, hemodynamic, peripheral shunting, mixed pathogenetic forms of hypoxia are distinguished.
At the same time, the lack of oxygen is a leading factor in all types of hypoxia, except tissue hypoxia. There is not only a decrease in the oxygen content in the tissues, but also a violation of the processes of its utilization. The end result of oxygen starvation is a deficit in the energy balance of the cell, a deficiency of oxidation substrates, a deficiency of enzymes, a decrease in the activity of coenzymes, and dissociation of oxidation and phosphorylation processes. An important role belongs to changes in the Krebs cycle, which is the main donor of hydrogen atoms and reduced forms of nicotinamide adenine nucleotides.
However, fetal hypoxia cannot be completely identified with a specific pO2 level, and even a significant decrease in the partial oxygen tension of a tissue (cell) still does not serve as an absolute indicator of a violation of its oxygen demand, since the metabolic activity of the cell itself, i.e., cellular pO2, can also be impaired. is not always a criterion for a hypoxic state, since with oxygen deficiency, a complex of compensatory-adaptive mechanisms is activated.
The main role in adaptation to hypoxia is usually played by an increase in cardiac output. Although, according to N. Alexander, during fetal hypoxia only a reaction in the form of bradycardia is noted, cardiac output remains at a constant level. Only in the hemic form of hypoxia, there is a decrease in cardiac output and blood flow in all organs by almost 30-50%, except for the brain, where a decrease in these functions occurs only by 9%. Redistribution of blood flow in the brain is noted. Hypoxia leads to vasodilation and the discharge of blood from the hemispheres into the brain stem. It is known that the reaction of the fetal brain to a change in the oxygen content is of a threshold nature: for example, a decrease in blood pO2 to 40 mm Hg. Art. does not entail changes in cerebral blood flow, but with a further decrease in pO_, cerebral blood flow increases sharply. The peculiarity of the preservation of blood flow in critical areas of the brain stem is rather a protective nature against the hypoxic factor and an explanation for the long-term survival of newborns under conditions of hypoxia. The reaction to a change in the partial voltage of carbon dioxide looks completely different. Any fluctuation in it leads to an increase or decrease in cerebral blood flow, a decrease in the electrical activity of the brain. An important role in the development of hypoxic syndrome belongs to the resulting acidosis, which has a significant effect on the permeability of vascular and cell membranes, tissue hydration, the rate of enzymatic catalysis, and blood clotting. Moreover, the degree of damage to organs and tissues depends on the duration and intensity of oxygen starvation, as well as on the adaptive capabilities of the fetus, the degree of maturity of its organs and systems.
The phenomena of metabolic acidosis are increasing. Oxygen deficiency and acidosis increase the permeability of cell membranes, as evidenced by the high activity of a number of intracellular enzymes (lactate-malate-succinate dehydrogenase).
The biggest changes occur in potassium balance. Strengthening catabolic processes leads to a decrease in the formation of ATP, as a result of which potassium is not absorbed. Intracellular potassium is replaced by sodium, which carries water into the cell space, as a result of which intracellular edema develops. Hyponatremia leads to extravascular edema of organs and tissues, facilitating the release of fluid from the vascular bed. Quantitative changes in electrolytes also lead to disturbances in the ratios of each electrolyte at the level of cell membranes. The ratio Napl / Kpl, Supl / Mgpl decreases, the ratio Kpl / Supl increases, which undoubtedly affects the cardiac activity of the fetus.
There is also a significant restructuring of carbohydrate metabolism. Thus, the lactate content increases in the liver of the mother, in the liver of the fetus and in the blood of the mother. At the same time, the patterns of lactate exchange in the direction of the mother are preserved? the fetus exchanging pyruvate is mainly the mother? the fetus, thereby providing the fetus with an important metabolic substrate. Strengthening anaerobic processes in the mother's body is a response to the hypoxic factor, providing the fetus with the necessary energy substrates.
With oxygen deficiency, the sympathetic-adrenal system is activated, as a result of which catabolic processes prevail in the body. Hypoxia, limiting the resynthesis of ATP in mitochondria, causes a direct depression of the functions of various systems of the fetus. The content of the biologically active and associated with plasma proteins fraction of cortisol increases. At the same time, a large amount of catecholamines is produced, and the content of norepinephrine in the blood is 2 times higher than the amount of adrenaline. Thyroid hormones also change their hormonal focus.
For a long time in obstetrics and neonatology, there was an idea that hypoxia primarily affects enzymatic processes involved in redox processes. However, at present, the idea that any pathological condition deviates from the biochemical status of the organism is becoming more widespread and is a manifestation of the functional or structural disorganization of biocatalytic systems and, first of all, the receptor apparatus of biomembranes.
Among the reasons for changes in the structure and function of biomembranes under the action of hypoxia, one of the leading is the violation of free radical reactions of lipid peroxidation. Violation of the systems of protection against excessive (LPO) leads to disruption of membrane systems, modification of cellular proteins, a decrease in the production of energy spent on maintaining the viability of the cell and the development of a pathological process.
The processes of decomposition reactions (catabolism) begin to prevail over the reaction of biosynthesis (anabolism), the mobilization of fats from the fat depot occurs, and the breakdown of triglycerides increases. The content of free fatty acids and acetone bodies increases, the amount of phospholipids and their metabolites decreases not only in full-term, but also in low-weight fetuses. The intensity of the oxidation of amino acids increases, the concentration of uric acid increases, the concentration of gamma-amino acid changes, the activity of monoamine oxidases.
It is necessary to note the change in the erythrocyte parameters of the umbilical cord blood, which can be considered as identical to the cellular composition of the fetal blood. So, according to the literature, the level of hemoglobin, hematocrit, the number of erythrocytes in the capillary blood of a newborn on the 1st day after birth is significantly higher than these indicators in the blood of the umbilical cord (on average 185 g / l, 56%, 5.3 per 1012 / l, respectively) ...
The indicators associated with the erythrocyte itself (the average volume of erythrocytes, the average content of hemoglobin in it) remain stable, that is, according to these data, one can judge the state of the erythron of the newborn.
With fetal hypoxia, there is a decrease in the number of erythrocytes, an increase in the average volume of erythrocytes, the average hemoglobin content in an erythrocyte, and erythrocyte cytosis. With a small fetal weight, a decrease in the hematocrit value, an increase in the average hemoglobin content in the erythrocyte with a tendency to an increase in the average volume of erythrocytes, a decrease in the total hemoglobin content and the number of erythrocytes were also revealed.
These data indicate that the presence of a hypoxic factor, gestational age, undoubtedly, affect the morphology of blood and the composition of erythron not only in the fetus, but also in the newborn.
Thus, the pathogenesis of the development of chronic hypoxia can be represented in the form of the following factors: violation of the processes of supply, transport and utilization of oxygen; placental insufficiency in the form of a violation of the transport, trophic, endocrine and metabolic functions of the placenta, etc. (Scheme 4).
In acute fetal hypoxia, rapid reflex reactions occur, aimed at enhancing the supply of the fetus with oxygen: an increase in the minute volume of the heart, heart rate, changes in intrauterine respiratory movements. This, at a certain stage, provides an increase in the stability of the fetus with mild or short-term hypoxia. Acute hypoxia, as a rule, occurs against the background of impaired uteroplacental circulation (morphofunctional disorders from the umbilical cord, placenta, abnormalities of labor). This is the most common cause of acute fetal hypoxia. This obstetric pathology can lead to cardiovascular failure, impaired respiratory function and other pathological changes in the body of a pregnant woman. All these changes can contribute to hypoxic damage to the vital functions of the fetus, including damage to the central nervous system and some parts of the brain.
In connection with the changes indicated in Scheme 4, it is necessary to carry out rational anesthesia of childbirth in women with fetal hypoxia and its low weight, because the use of narcotic analgesics without taking into account the condition of the fetus can cause irreversible hypoxic damage to brain cells and lead to antenatal and perinatal losses.
Modern methods of prevention and therapy of fetal hypoxia
For several decades, there has been an active search for ways to treat intrauterine fetal hypoxia, aimed primarily at eliminating metabolic acidosis, O2 deficiency, and increasing compensatory-protective mechanisms in the mother-fetus system in response to a lack of oxygen. It is known that various influences on the body in hypoxic conditions can create a certain conditionality and influence the mechanism of pathological effects.
Since the factor of hypoxia is assigned the leading pathogenetic significance in many urgent and non-urgent clinical situations, A.P. Kiryushchenkov's statement that “the development of effective measures aimed at preventing and timely correction of hypoxic conditions during pregnancy and childbirth is the most important task of obstetric science. and practice ".
There are various ways to prevent and treat fetal oxygen deprivation. Some of them have been well developed for a long time and have only been improved in recent years. The younger section is the physiological and therapeutic regulation of the uteroplacental circulation. It is this that is read as the main, critical function in supplying the fetus with oxygen. Inadequacy of maternal blood flow in the placenta is considered a major factor in fetal morbidity and mortality. The expanding arsenal of therapeutic methods with the help of drugs and physical methods makes it possible to correct the main manifestations of placental insufficiency (FPI) in the II and III trimester of pregnancy in a significant number of women. So, at present, pathogenetic pharmacotherapy can be classified as follows:
1. Means regulating uteroplacental and feto-placental circulation. These include vasodilators (beta-mimetics, aminophylline, theophylline); agents that normalize the processes of microcirculation (compliance, courantil, rheopolyglucin, heparin); estrogenic drugs (estrone, estradiol propionate, sygetin).
2. Means that regulate metabolic processes. These include drugs that activate glycolysis by enhancing energy production and primary phosphorylation of glucose (insulin, cocarboxylase, ATP); enhancing adequate glycolysis by blocking the release of catecholamines from granules (donors of sulfhydryl groups) and the activity of nodal glycolysis enzymes - phosphofructokinase (sodium bicarbonate, unitiol); activating metabolic reactions of the Krebs cycle, pentose phosphate cycle and the respiratory chain (sodium succinate, chlorpromazine, cytochrome C, sodium oxybutyrate); reducing oxygen consumption by tissues (gutimine), normalizing the acid-base state.
3. Means acting on the central mechanisms of regulation of functions. These are stimulants of the respiratory center (etymizole, corazole, etc.), drugs of the deprimating action of chlorpromazine, GHB.
Attempts to increase blood flow in the uterus by introducing substances that change the activity of the cardiovascular system (aminophylline, theophylline) are of interest, but, according to recent years, the use of drugs that selectively affect the uterus and its vessels is preferable. So, one of the estrogenic drugs, sygetin, increases the volumetric blood flow rate in the uterine vessels, the blood filling of the maternal part of the vessels, promotes the transfer of substances from the mother to the fetus, namely exogenous glucose. Sigetin is successfully used during pregnancy and childbirth with initial and pronounced signs of fetal hypoxia. There are also some negative aspects of this drug. Since sygetin causes uterine hyperemia, this can lead to a depletion of blood in other vital organs. This should be especially taken into account in hypoxia caused by blood loss. In addition, prolonged use of sygetin can lead to fetal growth retardation and the development of carcinogenic lesions. It was found that when using sygetin, hemorrhage may occur on the surface of the placenta in the absence of vascularization of its fetal part. Thus, the question of the possibility of using drugs of this class in the treatment of hypoxia is rather controversial, since the protective reactions of the mother, including the contractions of the vessels of the uterus, are very unfavorable for the fetus. With a drop in blood pressure caused by blood loss, the replenishment of the systemic vessels with blood from the uterus can be of great importance in increasing it in the mother and causing fetal aggravation.
Currently, beta-adrenomimetic agents have found widespread use for the treatment of fetal hypoxia, including in preterm labor.
The introduction of terbutaline, partusisten and other drugs favorably affects the indicators of the cardiotocogram, KOS pO2 of the fetus and newborn due to the relaxation of the contractile activity of the uterus, due to the stimulation of beta-adrenergic receptors. Magnesium sulfate has the same effect. It was revealed that the main effect of tocolytics on the fetus is the resulting changes in the cardiovascular system and fetal metabolism.
There has long been an opinion about the advisability of oxygen therapy in hypoxic conditions of the fetus, especially in low birth weight during pregnancy. At the same time, an increase in the intrapartum partial oxygen tension in the fetus normalizes not only its metabolism, but significantly increases the volumetric rate of uteroplacental perfusion. At the same time, therapy for fetal hypoxia, especially during childbirth, remains controversial. There are numerous studies showing that with an increase in pO_ in the mother's blood, this indicator in the fetus increases, the level of lactate decreases, and signs of hypoxia disappear. The positive effect of oxygen in fetal hypoxia caused by the entanglement of the umbilical cord, especially against the background of the use of vasodilators, is reported in their studies by G.F.Bykova et al. (1985). Along with this, there is information about a decrease in transplacental diffusion of oxygen, no change in blood oxygen saturation in the umbilical cord vessels, and even about the detection of acidosis and hypoxemia in the fetus with a high pO2 in the mother's blood. Long-term inhalation of oxygen can lead to hemodynamic disturbances - a decrease in blood flow through the ductus arteriosus, an increase in the resistance of the pulmonary vessels, to which the fetus responds by narrowing the vessels of the umbilical cord, the capillaries of the chorionic villi, and a decrease in the level of pO2 in the brain. Thus, when oxygen was inhaled by the mother, an increase in pO_ was found in the fetus from 12 to 23 mm Hg. Art., after 30 minutes with continued inhalation - a decrease in this indicator to 12 mm Hg. Art. Excessive hyperoxia can cause a change in the transport of amino acids, glucose, the mother may develop hyperoxic hypoventilation, which can lead to an increase in pCO2 in her blood and in the blood of the fetus. Thus, inhalation of hyperoxic mixtures by pregnant animals in 42% of cases did not cause changes in pO_ in the fetal brain, while in other cases it led to a reliably reversible decrease in pO_ and to respiratory failure associated with an increase in microvascular permeability. Moreover, the degree of decrease in pO_ depended on the severity of hypoxia in the mother's body.
Glucose is of great importance in the therapy of fetal hypoxia. Glucose is a valuable energetic, easily assimilated substance.
With the introduction of glucose, redox processes are enhanced, the deposition of glycogen in the liver is activated, the excretion of toxins from the body and metabolic processes are enhanced. Glucose has a stimulating effect on the uteroplacental circulation. Intravenous administration of glucose in the first and second half of pregnancy has a beneficial effect on the cardiac activity of the fetus, its motor activity, and increases the fetal's resistance to anoxia. However, in recent years, attention has been drawn to the high osmosis of glucose solutions, which can lead to hypernatremia. Hypernatremia can cause intracranial hemorrhage. Plasma hyperosmolality is especially dangerous in premature infants, which is due to insufficient development of the basement membrane of the brain capillary endothelial cells, which function as the blood-brain barrier. These changes can lead to the "opening" of the blood-brain barrier, which facilitates the development of intracerebral hemorrhages.
It was also revealed that an excess of glucose in the body of the fetus may not always be useful in its hypoxia. Thus, in the experiment it was shown that when a 40% glucose solution was administered to pregnant animals in combination with inhalation of oxygen under conditions of artificially created hypoxia, the desired positive effect was not achieved. An increase in lactate and pyruvate was found in the brain tissue of these fetuses. A decrease in respiratory movements was noted, which is a sign of fetal distress. With the introduction of glucose in childbirth, a number of authors note the appearance of jaundice in newborns, hypoglycemia and hyponatremia.
In addition, when glucose is administered with cardiotonic drugs against the background of oxygen inhalation, a short-term effect is noted, followed by an increase in lactate in the umbilical cord blood to 5.8 (1.1 mmol / l), a decrease in oxygen tension to 28.9 (1.6 mm Hg). Art.), an increase in metabolic acidosis - the pH of the blood from the fetal head to 7.15 (0.003) - and the accumulation of LPO products without significant changes in the activity of hormones of the pituitary-adrenal system. There is also a short-term stimulation of oxygen metabolism with practically unchanged oxygen delivery to the tissues. The complete depletion of oxygen reserves occurs 1.5 times faster than under conditions of narcotic action, with a subsequent deterioration of these indicators.
Based on the above data, the introduction of a 40% glucose solution with cardiotonic drugs against the background of oxygen inhalation in the presence of chronic or acute fetal hypoxia should be carried out with caution, taking into account the possibility of metabolic disturbances in the fetus.
The introduction of promedol (20-40 ml), sibazon (5-10 ml), as an anesthesia of labor, leads to inhibition of tissue respiration in the mother with impaired respiratory enzymes, an increase in the oxygen delivery time to 12.6 (1.7 s), a critical constant up to 12.4 (1.1 s), an increase in anaerobic processes of glycolysis, lactacidemia with a simultaneous activation of LPO processes in the umbilical cord blood, which indicates the possible occurrence of violations of the vital functions of the fetus and newborn, especially in the presence of a small fetus. Therefore, the method of choice for pain relief in labor in women with low birth weight, with hypoxia is the use of pharmacological protection of the fetus (electroanalgesia in combination with reduction for the mother with doses of GHBa - 28.4 mg / kg of body weight, sibazon - 0.07 mg / kg, droperidol - 0 , 03 mg / kg).
Pharmacological protection of the fetus helps to reduce the degree of acidosis: an increase in pH to 7.22 (0.01), lactate level from 6.2 (0.2) to 3.4 mmol / L, normalization of hormones of the pituitary-adrenal and thyroid systems of the fetus, indicators glycolysis, positive dynamics of CTG of a full-term fetus in 90.4%.
In the event of acute fetal hypoxia caused by abnormalities of labor, impaired uteroplacental blood flow, pharmacological protection of the fetus is performed by intravenous administration of sub-drug doses of drugs such as GHB. at the rate of 14.2-28.4 mg / kg of body weight of a woman, sibazon 0.07 mg / kg or droperidol 0.03 mg / kg. In the presence of a small fetus, a combination of GHB with sibazone is necessary (14.2 and 0.035 mg / kg, respectively). In case of positive dynamics on CTG, a repeated dose is administered after 45 minutes - 1 hour. If there is no effect, it is necessary to consultatively resolve the issue of early surgical delivery. Thus, in order to pharmacological protection of the fetal central nervous system from hypoxic damage in a woman in labor by fetal hypoxia and their low weight, to reduce the side effects of drugs on the fetus and newborn in the dynamics of childbirth, it is necessary to use drugs with antihypoxic action in doses reduced for the mother.
A person consists of two parts: the fruiting (chorion itself) and the maternal (the endometrium of the uterus - decidua basalis).
The fruit part from the side of the amniotic cavity is covered with amnion, which is represented by a single-layer prismatic epithelium and a thin connective tissue plate. V chorionic plate there are large blood vessels that came here along the umbilical cord. They are located in a special connective tissue - mucous tissue... Mucous tissue is normally found only before birth - in the umbilical cord and chorionic plate. It is rich in glycosaminoglycans, which determine its high turgor, so the vessels in the umbilical cord and in the chorionic plate are never pinched.
The chorionic plate is delimited from the intervillous space and maternal blood flow by a layer cytotrophoblast and fibrinoid(Mittabuha). Fibrinoid performs an immuno-biological barrier function. This is a “patch” at the site of damage to the cytotrophoblast, which prevents the contact of maternal blood with the blood and tissues of the fetus; it interferes with immune conflict.
In the intervillous space, villi of different diameters are determined. First, it is primary (main) villi... They can reach the deep layers of the endometrium and grow into it, then they are called anchor. Others may not come into contact with the maternal part of the placenta. Branching from the main villi of the first order secondary villi from which branch tertiary villi(usually final; only under unfavorable conditions of pregnancy or with a post-term pregnancy can further branching of the villi occur).
In the trophism of the fetus, it is mainly the tertiary villi that take part. Let's consider their structure. The central part of the villi is occupied by blood vessels, and connective tissue is located around them. At the first stages, the villus is delimited by a layer of cytotrophoblast, but then its cells merge and form a thick syncytiotrophoblast... Areas of cytotrophoblast remain only around the anchor plates.
Thus, a placental barrier is formed between the maternal and fetal blood. It is presented:
The endothelium of the capillaries of the villi,
Basement membrane of capillaries,
Connective tissue plate,
The basement membrane of the cytotrophoblast,
Cytotrophoblast or syncytiotrophoblast.
If the syncytiotrophoblast is destroyed, then a fibrinoid (Langhansa) is also formed in this area, which also acts as a barrier.
Thus, in the placental barrier, the main role is played by syncytium, which is rich in various enzymatic systems that ensure the implementation of the respiratory, trophic and partially protein synthesizing functions. Through the placental barrier, amino acids, simple sugars, lipids, electrolytes, vitamins, hormones, antibodies, as well as drugs, alcohol, drugs, etc. enter the mother's blood. The fetus gives off carbon dioxide and various nitrogenous toxins, and, in addition, fetal hormones, which often leads to a change in the appearance of the expectant mother.
The maternal part of the placenta is represented by an altered endometrium, into which the chorionic villi have grown (i.e., the main detached membrane). It is represented by fibrous structures and a large number of very large decidual cells, which are also related to barrier, trophic, regulatory functions. These cells partially remain in the endometrium after childbirth, preventing secondary implantation in this area. The decidual cells are surrounded by a fibrinoid (Rora), which generally fences off the maternal part of the placenta from the intervillous space. Rohr's fibrinoid also performs a barrier immunobiological function.