Embolism with amniotic fluid. Intrauterine Pressure Arterial pressure, the method of its measurement. Blood pressure in normal and pathological conditions
intrauterine pressure (tensio intrauterina)
pressure in the uterine cavity during pregnancy, due to the changing tone of the uterus and the presence of amniotic fluid.
1. Small medical encyclopedia. - M.: Medical Encyclopedia. 1991-96 2. First aid. - M.: Bolshaya Russian Encyclopedia. 1994 3. Encyclopedic dictionary of medical terms. - M.: Soviet Encyclopedia. - 1982-1984.
See what "Intrauterine pressure" is in other dictionaries:
- (tensio intrauterina) pressure in the uterine cavity during pregnancy, due to the changing tone of the uterus and the presence of amniotic fluid ... Big Medical Dictionary
BIRTH- BIRTH. Contents: I. Definition of the concept. Changes in the body during R. Causes of the onset of R ............................ 109 II. Clinical current of physiological R. . 132 Sh. Mechanics R. ................. 152 IV. Leading P .............. 169 V ...
I Childbirth Childbirth (partus) is the physiological process of expulsion from the uterus of the fetus, amniotic fluid and placenta (placenta, membranes, umbilical cord) after the fetus has reached viability. The fetus, as a rule, becomes viable after 28 weeks ... ... Medical Encyclopedia
The style of this article is not encyclopedic or violates the norms of the Russian language. The article should be corrected according to the stylistic rules of Wikipedia ... Wikipedia
PLACENTA- PLACENTA. Contents: I. Comparative anatomy............................55. 1 II. The development of P. in humans ................... 556 III. Placenta of a full-term fetal egg ..... 5E8 IV. Physiology and biology 11............55a V. Pathology P. Pat. forms II........j ... Big Medical Encyclopedia
Hard formations in the region of the mouth in animals and humans, used primarily for the primary mechanical processing of food, but also for the capture of prey, foraging, display of threat, attack, defense, and other purposes. In invertebrates... Collier Encyclopedia
- (CTG) continuous synchronous registration of the heart rate (HR) of the fetus and uterine tone with a graphical representation of the signals on the calibration tape. Heart rate registration is performed by an ultrasonic sensor on ... ... Wikipedia
ROLLS PREMATURE- honey. Premature birth Births occurring between 28 and 38 weeks of gestation. Premature is considered a child born at a gestational age of less than 37 weeks with low birth weight (500 2499 g), physical signs of immaturity and ... ... Disease Handbook
LABOR MANAGEMENT- honey. Rupture of the membranes can occur at any stage of pregnancy Signs Sudden discharge or leakage of clear fluid from the vagina. In full-term pregnancies, delivery usually occurs within 24 hours of rupture of the membranes ... ... Disease Handbook
ANETODERMIA ERYTHEMATOSA JADAS-SOHNI- (Yadasson), spotted idiopathic Figure 9. Richard's anemograph with a clockwork drum. some skin atrophy (atrophia cutis maculosa); sometimes, instead of a spot, the primary element is a papule. Three stages are clinically distinguished: 1) inflammation (red spot) ... Big Medical Encyclopedia
This page is a glossary. # A ... Wikipedia
Embolism amniotic fluid- a condition that occurs during pregnancy in the event of the penetration of elements of the fetal water into the mother's bloodstream and is accompanied by the development of acute cardiac and pulmonary insufficiency or circulatory arrest.
Such a complication is possible with an increase in pressure in the amnion higher than in the blood vessels of the uterus or gaping of the venous vessels of the uterus.
Causes that increase intrauterine pressure:
- - Excessive labor activity;
- - Quick delivery;
- - The use of large doses of oxytocin;
- - Polyhydramnios;
- - Large fruit;
- - Multiple pregnancy;
- - Breech presentation;
- - Dystocia of the cervix;
- - Post-term pregnancy;
- - Belated rupture of the fetal bladder;
- - Rough manipulations during childbirth (Kristellerat's reception).
Causes of gaping of the uterine vessels:
- - Hypovolemia of any origin;
- - Premature placental abruption;
- - Placenta previa;
- - Manual removal of the placenta from the uterine cavity;
- — C-section;
- - Hypotension of the uterus.
Clinical picture of amniotic fluid embolism depends on the volume and composition of the waters that have entered the blood vessels of the mother.
Diagnosis of amniotic fluid embolism is based on the assessment of clinical symptoms, laboratory examination and additional methods research.
Symptoms of amniotic fluid embolism:
- - Chills;
- - Cough;
- - Paleness or cyanosis;
- - in the chest;
- - Shortness of breath;
- - Decreased blood pressure;
- - Tachycardia;
- - Coagulopathic bleeding from the birth canal or other places;
- - Convulsions;
Laboratory signs - signs of hypocoagulation and increased ESR.
Additional research methods:
- ECG - sinus tachycardia, myocardial hypoxia, acute cor pulmonale.
- Radiological changes are detected immediately or several hours after the embolism and are characterized by a picture of interstitial confluent pneumonitis.
Differential diagnosis of amniotic fluid embolism is carried out with the following pathology:
- Myocardial infarction - pain, radiating to the left arm, rhythm disturbances, ECG changes, not always recorded with a fresh heart attack;
- Thromboembolism of the pulmonary artery: suddenness, suffocation, chest pain. It often happens with compromised veins (varicose veins, thrombophlebitis, phlebitis) right d, on the ECG;
- Air embolism (with a gross violation of the infusion technique);
- Mendelssohn's syndrome (bronchospasm in response to the ingress of acidic stomach contents into the upper respiratory tract) - acid-aspiration hyperergic pneumonitis. It happens, as a rule, on induction anesthesia with an empty stomach, when vomit enters the respiratory tract: anoxia for 5 minutes - death of the cerebral cortex.
Emergency care for amniotic fluid embolism is carried out by a team consisting of an obstetrician-gynecologist and an anesthesiologist. Necessary consultations , vascular .
Management of amniotic fluid embolism:
1. During pregnancy - urgent delivery.
2. Treatment of cardiopulmonary shock or conduction of cardiopulmonary
resuscitation.
3. Correction of coagulopathy.
4. Surgical intervention for bleeding.
Priority actions for:
1. In case of circulatory arrest - CPR.
2. With an increase in signs of respiratory failure - tracheal intubation and mechanical ventilation with 100% oxygen with PEEP + 5 cm of water st.
3. Puncture and catheterization of the subclavian or internal jugular vein with CVP control. Sampling of 5 ml of blood for a coagulogram and examination for the presence of elements of amniotic fluid.
4. Catheterization Bladder indwelling catheter.
Monitoring of vital signs should include:
- Measurement of blood pressure every 15 minutes;
- CVP;
- heart rate;
- BH;
— Pulse oximetry;
-ECG;
-Hourly diuresis and urinalysis;
— Thermometry;
- X-ray of the chest cavity;
- ; platelets;
- Coagulogram;
- Acid-base state and blood gases;
— Biochemical analysis of blood and electrolyte content.
Further treatment tactics:
1.If CVP<8 см вод. ст. — Коррекция гиповолемии путем введения коллоидов и кристаллоидов в соотношении 2:1. В случае возникновения кровотечения в состав инфузионной терапии включают свежезамороженную плазму. Не использовать 5% альбумин.
2. When CVP> 8 cm of water. Art. inotropic support is carried out: dopamine (5-10 mcg/kg/min) or dobutamine (5-25 mcg/kg/min.). Start isotropic therapy with minimal doses, and in the absence of effect - gradually increase them. It is advisable to use the combined administration of dopamine (2-5 µg/kg/min) and dobutamine (10 µg/kg/min).
3. Simultaneously with sympathomimetic therapy, glucocorticoids are used: prednisolone up to 300-400 mg or hydrocortisone -1000-1500 mg.
4. Fight against coagulopathy (according to the protocol for the treatment of DIC).
Criteria for the effectiveness of intensive care for amniotic fluid embolism:
- - Increased cardiac output;
- - Elimination of arterial hypotension;
- — Elimination of signs of peripheral vasoconstriction;
- – Normalization of diuresis> 30 ml / hour;
- — Normalization of hemostasis indicators;
- - Reducing signs of respiratory failure.
Criteria for stopping IVL:
- — Stabilization of the clinical condition of the patient;
- - Respiratory rate less than 30 per minute;
- - Inspiratory effort is less than -15 cm of water. Art.;
- - PaO2 / PiO2> 80 mm Hg. Art. / 0.4 at PEEP 7 cm of water. Art.;
- -. The ability of the patient to independently double the volume of exhaled air per minute.
The blood supply to the uterus comes from two sources: from the uterine artery (a. uterina), originating from the internal iliac artery (a. iliaca interna), the ovarian artery (a. ovarica). The uterine artery goes at the base of the broad ligament, reaches the lateral wall of the uterus and, at the level of the internal os of the cervix, turns upward, giving off the vaginal artery (a. vaginalis), which runs along the anterolateral wall of the vagina, feeds its upper third and connects to the same branches of the opposite side . The upper part of the uterine artery is divided more often into two, sometimes into three branches, of which one goes to the bottom of the uterus, the other to the mesentery of the ovary.
The arterial vessels of the myometrium show independent contractile activity, regardless of the contractile activity of the uterus, especially in the subplacental zone. Spontaneous contractions of the arteries of the human uterus outside of pregnancy are characterized by two vascular rhythms. The first type of rhythmic contractions is 2-3 contractions in 10 minutes (typical for the first phase of the menstrual cycle with high estrogen saturation). The second type is in the second phase of the menstrual cycle, when there is a significant increase in the amplitude of contractions; the main rhythm of contractions of the vascular wall is superimposed by rapid contractions of the arteries with a very low amplitude and high frequency.
Spontaneous contractile activity of the arteries, which causes instantaneous changes in the lumen of the vessels, is a decisive factor in maintaining a continuous and optimal blood supply to the uterus.
The ovaries and fallopian tubes receive blood from the ovarian artery, which originates from the abdominal aorta and descends into the pelvis along with the ureter. Having reached the ligament that suspends the ovary, the ovarian artery approaches the hilum of the ovary and gives off part of the branches. The other part anastomoses with the uterine artery.
Arteries are accompanied by veins of the same name, which form powerful venous plexuses in the parametrium, anastomosing with each other (bladder, uterine, rectal, ovarian). The myometrium contains multiple venous collectors.
There are no valves in the veins of the uterus that prevent the backflow of blood. The venous system, which receives a large amount of blood (up to 1 liter), is a kind of hydrodynamic system that regulates the outflow from the myometrial and placental circulation circuits.
During labor, part of the venous blood is deposited in the venous collectors of the uterus, thereby providing an almost constant pressure in the intravillious spaces.
During pregnancy, along with an increase in the mass of myometrium in the wall of the uterus, additional arterial and venous vessels are formed, as a result of which the uterus is a tangle of vessels. A healthy young woman maintains a stable number of vessels in the uterus. However, the vessels of the uterus change greatly during gestation. During pregnancy, the number, length, tortuosity of arterial and venous vessels increase many times over. Numerous arteriovenous and arterio-arterial anastomoses are formed. Between the layers of the myometrium, especially between the inner and middle ones, numerous venous cavities (settlers, collectors) are formed, which are necessary for the deposition of venous blood. The walls of the venous cavities are structurally connected with muscle bundles that separate and unite individual muscle layers of the myometrium. The venous cavities form the basis of the separating layers and are called the separating venous sinus.
The spiral arteries pass through the myometrium and the basal lamina and reach the intervillous space, where they completely lose their muscle and elastic fibers.
During pregnancy, the main spiral arteries eject the blood in them due to characteristic contractions directed towards the center of the intervillous space, from where the blood diverges towards the subvillous plate. After passing through the narrow intervillous space, the blood returns through the venous channels of the placental septa and reaches the spongy layer of the uterus. Up to 1/3 of venous blood passes through the drainage in the marginal sinus every minute.
In the intervillous space of the maternal part of the placenta, arterial circulation is combined with venous circulation.
In the fruiting part of the placenta there is also a network of capillary vessels between the arteries and veins of the umbilical cord. These structures form in the intervillous space, as it were, "cushions" from the capillary vessels of the fetus, which facilitates placental exchange.
The volume of the vascular bed and the blood flow of the uterus during pregnancy increase many times over. Vascular resistance with the onset of pregnancy decreases by 30-40%.
During pregnancy, in terms of blood supply, the uterus is equated to vital organs (heart, brain), outside of pregnancy, the uterus is supplied with blood as peripheral organs.
Spontaneous contractions of the myometrium and the vessels themselves regulate the flow of arterial and outflow of venous blood. Of great importance is the diameter of the vessels. The narrowing of their lumen by 50% leads to a 16-fold increase in vascular resistance, therefore, diseases and complications of pregnancy associated with vasospasm (hypertension, late preeclampsia, the presence of myomatous nodes in the thickness of the myometrium, as well as an increase in the basal tone of the uterus) can cause prolonged ischemia of the uterus, increasing its contractile function and the development of fetoplacental insufficiency (premature termination of pregnancy).
The blood flow in the uterus depends on the content of hormones in the blood (estrogens, progesterone), as well as mediators of the sympathetic and parasympathetic systems.
The vessels of the uterus are innervated by a large number of sympathetic nerves. The postganglionic nerves, arising from the pelvic and para-aortic plexuses, form a perivasal network that runs along the blood vessels. Parasympathetic fibers have a similar course.
At present, a close interdependence of the basal tone and contractile activity of the uterus with the intensity of blood supply and blood flow in the myometrium has been established.
Initially, the blood supply may change, and then the motor function of the uterus is disturbed, which occurs in pregnant women and women in labor with myomatous nodes [Sidorova I. S., 1979, 1985, 1999, 2003]. At the same time, prolonged uterine hypertonicity is accompanied by a decrease in blood flow in the myometrium against the background of unchanged central hemodynamics.
During pregnancy, spontaneous contractile activity of the uterus is irregular. In the first half of pregnancy, these are contractions of low amplitude and high frequency. They play an important role in ensuring the normal blood supply to the myometrium.
In the second half of pregnancy, spontaneous uterine contractions are characterized by a higher amplitude and lower frequency, which turn into prenatal contractions in the last month of pregnancy. Contractions of the myometrium regulate the flow of blood to various parts of the uterus, contributing to sufficient perfusion of the myometrium.
The blood flow fully provides the trophic needs of the myometrium and adequate supply of the fetus, but the blood supply is different, therefore, myometrial and uteroplacental blood flow is isolated. The intercellular substance in the myometrium is connected to its capillary system, and therefore the reaction of the vascular bed significantly affects the metabolism of myometrial cells. A decrease in myometrial blood flow leads to insufficient supply of the uterus with oxygen, glucose, biologically active compounds and hormones.
Violation of hemodynamics as a result of uterine hypertonicity can lead to impaired metabolism of smooth muscle cells and "biochemical injury of the myometrium", which is expressed in a decrease in the elasticity and elasticity of muscle tissue. This can cause a rupture of the uterine wall during difficult childbirth (the so-called Verbov uterine rupture).
The state of blood vessels and blood circulation in the uterus are decisive factors in maintaining metabolic processes in the myometrium at an optimal level.
There are two groups of factors affecting the vascular bed of the myometrium. The first group - factors that reduce blood flow: these are mediators of the sympathetic nervous system(catecholamines), vasoconstrictors, increased uterine basal tone. The second - factors that increase blood flow: mediators of the parasympathetic nervous system (acetylcholine), β-blockers, β-adrenergic agonists, as well as β-adrenergic receptor stimulants (partusisten, ginipral), antispasmodics (no-shpa), estrogens, inhibitors of prostaglandin synthesis (indomethacin) , GABA (phenibut), etc.
The vessels of the uterus, like the cells of the myometrium, have two types of adrenergic reception. Agents that excite adrenoreceptors cause vasoconstriction, while agents that excite β-adrenergic receptors lead to their relaxation.
Under normal conditions, the sympathetic and parasympathetic subsystems are in a state of dynamic equilibrium, which ensures normal contractile activity of the uterus both during pregnancy and outside of non-pregnancy, as well as its optimal blood supply.
Violation of this balance leads either to the functional dominance of the sympathetic system, which causes uterine ischemia (increase in its tone, hyperexcitability), or to the predominance of the tone of the parasympathetic nervous system, in which dilation of the blood vessels of the uterus and venous congestion are observed. Both of these disrupt the biochemical processes and energy of uterine contractions.
Hemodynamics in the uterus is a complex process and is closely related to its contractile function.
The myometrial circuit includes arteries, arterioles, capillaries, venules, veins and venous depot, venous outlet collectors (venous sinuses). Before delivery, the myometrial circuit contains 800-1000 ml of blood, of which 80-85% flows through the utero-placental circuit and only 15-20% remains in the uterus.
The uteroplacental circuit includes 100 to 200 spiral arteries that empty into the intravilli spaces. Their total capacity is 400-500 ml. The spaces are drained by short venous trunks that flow into the venous depots of the uterus. It should be emphasized that the drainage system in both vascular circuits is the same - it is the venous sinus of the uterus, which combines both circuits into a single hydrodynamic system.
Although both circuits, myometrial and uteroplacental, function independently of each other, they are closely related to the contractile activity of the uterus. During a contraction, endoamniotic and intramyometrial pressure increases, as a result of which myometrial blood flow increases and placental blood flow decreases. By the end of the contraction, all indicators characterizing the blood flow in both vascular circuits are fully restored. The period of relaxation of the uterus passes against the background of hemodynamics restored to the initial level.
The increase in blood supply to the myometrium during the pause between contractions is due to the inclusion of deposited blood from the vascular reservoirs of the uterus (250-300 ml of blood), which is necessary for biochemical reactions.
The coordinated nature of labor activity is supported by compensatory-adaptive mechanisms that allow maintaining uteroplacental blood flow at the required level.
By modern ideas, intrauterine pressure and basal tone of the myometrium are the main regulators of blood flow in the vessels of the uterus, intravilli and in the placenta. With too long and strong contractions, an excessively high basal tone of the uterus, the blood flow through the placenta is significantly reduced (up to complete cessation), which can cause intrapartum fetal death.
It has been established that the critical pressure in the amnion cavity, at which the blood flow in the intravillous space completely stops and fetal asphyxia occurs, is a pressure above 30 mm Hg. Art. (35-50 mm Hg). In this case, the vessels are pinched by the contracted myometrium, the blood volume decreases until it stops.
Intramyometrial pressure over 30 mm Hg. Art. possible with severe discoordination of labor, as well as with prolonged attempts.
In most cases, in the process of physiological childbirth, oxygen and metabolic reserves are sufficient, and due to this, there are no significant disturbances in the blood circulation of the fetus. A decrease in uterine blood flow by 20% from the initial level cannot but affect the condition of the fetus, and a decrease by 25% causes fetal hypoxia.
Frequent (over 5 in 10 minutes) and prolonged contractions, especially against the background of increased basal uterine tone, already after 20-30 minutes lead to impaired uteroplacental circulation and a decrease in fetal heart rate. If the contractile activity of the uterus is not normalized, there is a danger of progression of asphyxia or hemorrhage in the brain.
The degree of passage of oxygen through the placental barrier is important. The amount of oxygen depends on the volume of the flowing blood, the content of hemoglobin and the partial oxygen tension of the blood.
With discoordinated contractions (long, frequent against the background of high basal uterine tone), too little blood (less than 300 ml) enters the intervillous space, resulting in increased pressure in the venous system of the uterus (danger of premature detachment of the placenta during childbirth).
Under normal conditions, the placenta is as if pressed by the pressure of the amniotic fluid and a certain intrauterine pressure. If the pressure in the venous system exceeds the allowable pressure of the intervillous space, premature detachment of the placenta may occur. This complication often accompanies discoordinated labor activity.
The oxygen consumption of a full-term fetus weighing 3500 g is 15 ml/min. Under normal conditions, there is a certain safety margin between the fetus's need for oxygen and its availability. The content of hemoglobin in the blood and the degree of oxygen saturation play an important role in the normal oxygenation of the fetus. A decrease in hemoglobin levels to 50 g / l and a decrease in blood oxygen saturation to 30% are critical (the fetus dies).
Common causes of impaired oxygenation of the fetus are uterine ischemia, circulatory failure, low cardiac output in the mother, impaired uteroplacental circulation, and a decrease in the functioning surface of the placenta.
The blood flow in the uterus decreases with a high basal tone, with excessively frequent and prolonged contractions and attempts. It depends entirely on the amplitude, frequency and duration of uterine contractions.
With excessive excitation of the adrenergic receptor system of the myometrium, a prolonged spasm of the uterine and peripheral vessels develops, vascular resistance increases, and uterine blood flow decreases.
A similar situation is often observed in the second stage of labor, so prolonged attempts not only have an adverse effect on the fetus, but are also a risk factor for the development of hypotonic uterine bleeding.
The blood pressure in the intervillous space during the relaxation of the uterus is equal to the difference in pressure between the arterial and venous blood at rest. In the intervals between contractions, it averages 10 mm Hg. Art., which corresponds to the average endoamniotic pressure.
During the peak of the contraction, the inflow of arterial blood into the intervillous space and the outflow of venous blood decrease, but in the pause between contractions it quickly recovers. Endoamniotic and intramyometrial pressure during contraction also increases, but the pressure difference in the intravillious spaces remains constant.
In the process of coordinated labor contractions, the oxygen and metabolic reserves of the blood located in the intravilli spaces support the vital activity of the fetus for at least 3 minutes with a complete cessation of blood circulation. In the case of chronic placental insufficiency, the energy reserves of the fetus are significantly reduced and this reserve time is absent.
An increase in endoamniotic and myometrial pressure during a prolonged contraction is accompanied by a decrease in blood supply to the uterus and a decrease in blood flow to the fetus, which is reflected in the fetal heart rate (decrease).
Thus, the vascular plexus of the uterus is functionally associated with its contraction and relaxation (systole - diastole contractions). Mechanical vibrations of the myometrium are transmitted to the walls of the vessels, causing the mass of blood to move either to the lower segment and the cervix, or back. This increases pressure on the internal os and cervix. Peristaltic blood waves propagate in the middle layer of the myometrium, and it is not possible to determine (feel) them with a hand. The role of a discrete blood wave that opens the cervix during childbirth is recognized by many researchers.
Recognition of the initial symptoms of violations of the motor function of the uterus during childbirth, a comparative assessment of the effectiveness of the treatment of anomalies of labor activity on the basis of clinical observations alone are very difficult, therefore, methods of monitoring monitoring during pregnancy, even at home, during childbirth - external and internal hysterography, cardiotocography.
Per last years Widespread in obstetric practice are the methods of recording the contractile activity of the uterus by external multichannel hysterography, as well as internal hysterography (tocography) using the radiotelemetric device of the Capsule system, the transcervical method of recording intrauterine pressure using the technique of an open polyethylene catheter, the method of transabdominal study of intrauterine pressure. Steer et al. developed a more advanced catheter for recording intrauterine pressure in the form of a transducer, which does not have the disadvantages of an open catheter. In 1986, Svenningsen and Jensen developed a fiber optic catheter for measuring intrauterine pressure. Utah Medical Systems has now developed the Intran 2 catheter.
Much attention to this problem, its solution is due to the serious importance of studying the contractile activity of the uterus for the diagnosis and prognosis of childbirth in their complicated course.
The first who tried to measure the force of uterine contractions during childbirth was the domestic scientist N. F. Tolochinov (1870), who proposed a spring manometer mounted in a cylindrical vaginal mirror. The manometer was brought to the fetal bladder and measured the strength of its pressure. In 1913-1914. The French obstetrician Fabre was the first to conduct a parallel recording of the contractile activity of the uterus using external and internal hysterography and came to the conclusion that the curves obtained when registering contractions by both methods correspond to each other. In 1872, Schatz applied internal hysterography, which is still widely used today.
At the same time, it is important to note that the data obtained during the simultaneous recording of amniotic pressure with a catheter inserted through the abdominal wall and transcervically showed complete identity of the obtained curves. According to Mosler, the basal tone is 15 mm Hg. Art., the value of intrauterine pressure in the first stage of labor - 60 mm Hg. Art., in the II period - 105 mm Hg. Art. Filed by Alvarez, Caldeyro-Barcia, these figures were respectively 8 mm, 35-100 mm Hg. Art. and 100-180 mm Hg. Art. According to Williams, Stallwoithy, indicators of contractile activity of the uterus were respectively 8 mm Hg, 40-90 mm Hg. Art., 120-180 mm Hg. Art. Williams, Stallworty point out that internal hysterography has the advantage of reflecting pressure in the hydrostatic cavity, so readings based on hydrodynamic calculations reflect the true activity of uterine contractile function.
Some authors use closed polyethylene tubes with one sensor and a pressure sensor that is located between the wall of the uterus and the fetal head along the largest circumference of the fetal head to measure intrauterine pressure. However, in obstetric practice, there are many examples showing that quite often there is no correspondence between the clinical course of childbirth and hysterography indicators.
Over the past 50 years, a large number of factors (hormones) and various pharmacological substances on the uterus have been studied. Mechanical factors also have a fairly long history. Back in 1872, Schatz showed that a sudden increase in the volume of the uterus leads to the occurrence of uterine contractions. Reynolds in 1936 proposed the theory of uterine tension ("a uterine distention theory"), in 1963 Csapo - the theory of the "progesterone block", considered by the author as a mechanical factor in pregnancy.
At the same time, the physical laws of hydrodynamics can and should undoubtedly be applied to the study of the contractile activity of the uterus. For the first time in 1913 Sellheim in the monograph "Childbirth in Man" made a number of calculations on a hydrodynamic basis, these studies are reflected in many textbooks of domestic and foreign obstetricians. The monograph by Reynolds (1965), devoted to the physiology of the uterus, provides detailed calculations showing the role of physical factors in uterine activity with a hydrodynamic substantiation according to the laws of Laplace, Hooke. Referring to research by Haughton, conducted back in 1873, he showed that the proportion of the bending radius in the fundus of the uterus and the lower segment of the uterus is equal to 7:4, i.e., the difference in tension of the uterus in its upper and lower sections has a ratio of 2: 1 and therefore, in the process of normal childbirth, there is a clear difference in the tension of muscle fibers in the fundus and lower segment of the uterus, this equally applies to the thickness of the myometrium in these sections, which correlates as 2:1. Therefore, the force is proportional to the thickness of the Haughton uterine tissue. Based on the calculations and ideas of Haughton and his own data based on the method of three-channel external hysterography developed by Reynolds in 1948, the author believes that cervical dilatation is observed only when rhythmic activity in the uterine fundus predominates over the rest of its areas. At the same time, in the middle zone of the uterus (body) in relation to its bottom, contractions are less intense and they are usually shorter in duration and their frequency decreases as labor progresses. The lower segment of the uterus remains inactive throughout the entire first stage of labor. Thus, the dilatation of the cervix during childbirth is the result of decrease in the gradient of physiological activity from the bottom to the lower segment of the uterus. The functional components of this activity are the intensity and duration of uterine contractions. At the same time, contractions of the uterus in the fundus are longer by 30 s than in the body of the uterus, i.e., the so-called "triple downward gradient" is observed. These judgments of the author were confirmed by the works of Alvarez, Caldeyro-Barcia (19S0), who measured and evaluated intrauterine and intramuscular pressure in the uterus at various stages of pregnancy and childbirth using a complex microballoon technique. Using this method, it was possible to confirm the concept of a "triple downward gradient", characteristic of the normal course of childbirth. In addition, it was shown that the wave of contractions began in one of the tubal angles of the uterus, and the theory of the dominant role of the uterine fundus and the presence of a triple downward gradient was also confirmed.
Similar judgments about the application of the laws of hydrodynamics in the study of uterine dynamics are also given in the monograph Mosier (1968). According to the author's concept, two opposing forces control and complete the generic process: tension force and elasticity. However, the author emphasizes that it is impossible to transfer the results of the study of uterine contractions to animals and to the human uterus without reservations, as described in the work of Csapo et al. (1964), since animals have a bicornuate uterus, and humans have a simplex. Therefore, both studies on the human uterus are needed, as well as taking into account some discrepancies between the laws of hydrodynamics and clinical observations. So, at the maximum tension of the walls of the uterus, a decrease in the resistance of the walls of the cervix is simultaneously observed. At the same time, the contractile activity of the uterus during childbirth does not occur due to an increase in intrauterine pressure, but by an increased tension of the walls of the uterus, which occurs as a reaction to an increase in the total volume (diameter) of the uterine cavity. It should be noted here that the increase in the volume of the uterus that occurs during pregnancy occurs without a noticeable increase in pressure in the uterus, where the pressure varies from 0 to 20 mm Hg. Art. and an increase in pressure is planned only at the end of pregnancy. Bengtson (1962) registered average values of intrauterine pressure at rest, during pregnancy, equal to 6-10 mm Hg. Art. The nature of this "resting pressure" - residual or basal pressure according to Mosler is not entirely clear in detail, but, obviously, it is causally partially connected with the intrauterine pressure itself and intra-abdominal pressure, as Sellheim pointed out back in 1913.
Mosler emphasizes that the measurement of intrauterine pressure is an indirect determination of the tension of the uterine wall due to contractions of the uterine muscles and also depends on the radius of the uterine cavity. The tension of the uterine wall can be described by the Laplace equation. At the same time, one cannot but pay attention to the fact that when using the microballoon technique (from 1 to 15 mm in volume), the rubber balloon, during long registration, gives relatively inaccurate pressure data based on changes in elasticity.
An important point for obtaining identical data is, from our point of view, the exact determination of the depth of the catheter insertion into the uterine cavity, which, unfortunately, is not taken into account when performing internal hysterography, since the authors proceed from the misconception about the same pressure in the uterine cavity in the process of childbirth, based on Pascal's law. Only in the work of Hartmann, when studying intrauterine pressure outside of pregnancy, it is indicated that all catheters have a mounted ring at a distance of 5 cm, showing the depth at which the catheter is located in the uterine cavity. However, as will be shown later, when determining intrauterine pressure indicators, it is necessary to take into account the height of the hydrodynamic column - the height of the uterus and the angle of the uterus in relation to the horizontal line, and depending on the angle of the uterus in the lower sections of the uterus, the pressure will be higher than in the overlying sections of the uterus (bottom).
The study of the contractile activity of the uterus using five-channel external hysterography during normal labor, even accompanied by painful contractions, revealed the absence of discoordination of labor activity. Those insignificant differences in the duration and intensity of contractions of both halves of the uterus at the same level (in one segment) do not matter, because its contractions remain coordinated and the amplitude of contractions reaches its highest point simultaneously in all recorded segments of the uterus, which allowed us to move on to a three-channel external hysterography, placing the sensors, respectively, the area of the bottom, body and lower segment of the uterus.
The data obtained were analyzed by quantitative processing of hysterograms every 10 min. The main parameters of the contractile activity of the uterus were studied (duration and intensity of contractions, frequency and duration of pauses between them, coordination of various parts of the uterus among themselves, etc.). Currently, electronic integrators are used for this purpose when the area of active pressure under the intrauterine pressure curve is measured, especially when using internal hysterography.
Some authors consider the uterus to be a pronounced organ of movement, which manifests itself both in its continuous contraction (tonus) and in periodic contractions (contractions) observed in pregnant women, women in labor and puerperas. The completion of the physiological role of the uterus, as a fetus-place and organ of movement, is the process of childbirth - the development of fruit-expelling forces.
The process of childbirth differs from the actual uterine contractions in the extra-pregnant state and during pregnancy. The fructifying forces are a complex of contractions of the uterus (contractions) and contractions of the abdominal press (pulls) that join them in the second stage of labor. Some role is also played by contractions of the muscles of the vagina.
Contractions are regular, periodically repeated contractions of the smooth muscles of the body of the uterus (hollow muscle), which do not obey the will of the woman. A woman in labor can only strengthen or weaken to a certain extent. Attempts are observed during the second and third periods of the birth act.
According to Ya. F. Verbov, Bumma and others, labor pains are peristaltic in nature towards the exit of the birth canal. However, peristalsis in the human uterus is difficult to observe, since the wave of contraction spreads too quickly throughout the organ.
According to Ya. F. Verbov (1912), the muscle fibers in the uterus are mutually perpendicular; they are antagonistic and cannot contract at the same time. The onset of childbirth is characterized by the fact that the bottom of the uterus gradually begins to descend and by the end of the period of disclosure is 3-4 fingers below the obvious process. The uterus shortens due to the opening of the cervix and at the same time noticeably increases in width and in the anteroposterior direction. All this happens under the influence of contraction of the longitudinal fibers of the uterus in the first stage of labor. At the very end of the opening period, the contractions are more sensitive precisely because at this time the contractions of the longitudinal muscles are most energetic.
Figure: The size and shape of the uterus at the beginning (a) and at the end (b) of the period of disclosure (Ya. F. Verbov).
After the opening of the fetal bladder, the shape of the uterus changes dramatically, becoming narrow and long, the bottom of the uterus rises. At the beginning of the second period, the bottom of the uterus is one transverse finger below the xiphoid process; when the fetal head cuts and erupts, the bottom of the uterus goes under the edge of the ribs, its width decreases (20-18 cm). During this period, the circular muscle fibers of the uterus are reduced.
Figure: The size and shape of the uterus at the beginning of the period of exile (Ya. F. Verbov).
Figure: The size and shape of the uterus at the end of the period of exile; the uterus arches anteriorly (Ya. F. Verbov).
In the first stage of labor, the longitudinal muscles are supported at the site of attachment of the round ligaments and in the fascia pelvis; the abdominal press is not involved in contractions. In the second period, the uterus arches anteriorly, stretches the fascia of the abdominal wall, as a result of which the muscles of the latter are strongly contracted. The muscles of the abdominal wall put pressure on the uterus, flatten it, and the uterus, resting its bottom against the overlying organs and the anterior abdominal wall, acquires a great expelling force. In this alternation of the work of the longitudinal and circular muscles, Ya. F. Verbov sees the "law of the peristaltic movement of the uterus", since "peristalsis is the movement carried out by the alternating work of the longitudinal and transverse muscles."
Regarding this theory, it must be said that the clinic of childbirth is presented by the author correctly, but the definition of peristalsis and its “law” is incorrect, since peristaltic movement is a rapidly alternating contraction of both longitudinal and transverse muscles, and not a contraction according to the periods of childbirth, as described by I F. Verbov.
In the first stage of labor, a phenomenon called retraction occurs in the muscles of the uterus. It consists in the following: with each contraction of the hollow muscle, the arrangement of the muscle fibers mutually changes, and the fibers that lie one after the other before the contraction now lie in parallel; part of the fiber, rising higher, wedged among other fibers. The fibers retain their new position even after the contraction. A new fight leads to a new, even more significant displacement of muscle fibers. Ultimately, with increased labor activity, retraction leads to thickening and shortening of the hollow muscles of the uterus. Simultaneously with retraction, another process occurs - distraction, that is, stretching of the muscle fibers of the neck. Distraction occurs due to the fact that during retraction, the longitudinal muscle fibers of the hollow muscle pull up the circular fibers of the neck, which gradually stretch. Due to the retraction of the fibers of the hollow muscle and the distraction of the neck, the border between the hollow muscle and the lower segment is indicated as a muscle roller or retraction ring.
Figure: Retraction of muscle fibers in the uterine wall during childbirth.
a - stretched muscle; b - contracted muscle.
A - artery; B is a vein.
The next feature of uterine contractions during childbirth is their segmental nature. We can assume that the uterus consists of two functional sections - the body and the cervix. A possible boundary between them lies at the internal pharynx. The synergistic action of the sympathetic and parasympathetic nervous system in childbirth leads to the excitation of contractions of the body and the simultaneous relaxation of its neck.
The segmental nature of contractions can sometimes be observed in the lateral sections (horns) of the uterus. And, indeed, during childbirth, one can sometimes notice that contractions of the uterus are observed only on one side of it, while the other almost does not contract at all. From the point of view of the laws of development, this phenomenon is explained by a return to the type of functions usual for a bicornuate uterus. From a physiological point of view, the more developed the uterus, i.e., the more complete the fusion of the Mullerian ducts, the more coordinated the movements of the entire organ during labor.
Such segmentation of uterine muscle contractions, both vertically and horizontally, will be understandable if we take into account that the muscle fibers in the uterus are perpendicular or oblique to each other.
Recently, the significance of the tone of the uterus and the amplitude of its contractions for the course of labor has been clarified. With uterine contractions of the hollow muscle, some of the fibers move upward from the isthmus and cervix. At the same time, if the general resting tone of the uterus is low, then before contraction occurs, the walls of the uterus should gradually come into a state of tension. If the resting tone is high, then the slightest contraction of the motor part of the uterus will be reflected in the neck, the fibers of which, in a state of tension, will come quickly and cause it to open. Thus, the significance of the initial high tone of the uterus is the rapid transfer of the force of contractions of the motor part of the uterus to the pharynx, and the opening of the latter occurs quickly. Another meaning of a good uterine tone is to maintain the cervical dilatation at the achieved level. Thus, we consider a moderately high tone as a favorable phenomenon for the rapid opening of the cervix and the rapid course of labor. On the other hand, excessively high uterine tone can cause significant pain in the absence of contractions and spastic weakness of labor.
There is a complete relationship between the resting tone and the amplitude of contractions: with an increase in the resting tone, the amplitude of contractions decreases. A small amplitude of contractions does not affect the course of labor if the tone is good.
The following information is available about intrauterine pressure. Intrauterine pressure before delivery is 20 mm Hg. Art. During childbirth, intrauterine pressure fluctuates: outside of contractions, it averages 50 mm, at the height of the contraction it is about 80 mm, and with contraction of the abdominal press, it is about 95 mm Hg. Art. Distribution of intrauterine pressure during dilatation. The high blood pressure of the blanket (measured during caesarean section through the umbilical cord), reaching 160-180 mm, explains the relative harmlessness to the fetus of high intrauterine pressure during contractions and attempts. The relationship between intrauterine and arterial pressure during childbirth is such that an increase in intrauterine pressure during labor is accompanied by an increase in maternal blood pressure by 10-20 mm.
Figure: Distribution of intrauterine pressure during deployment (scheme).
During the contraction, there is a decrease in blood pressure in the vessels of the placenta, and the latter is partly bled. The ischemia of the uterus that develops during contractions threatens the fetus with asphyxia, therefore, at the time of penetration and eruption of the head, when the intrauterine pressure is especially high, the risk of fetal asphyxia increases.
An objective study of the contractions of a woman's uterus, especially during childbirth, presents significant difficulties.
Winkel's method - a study with a hand laid flat on the stomach at the bottom of the uterus, counting the duration of each contraction and pause in the second hand of the clock - primitive and inaccurate.
The applied methods of instrumental study of uterine contractions can be divided into two groups:
1) internal hysterography - the study of uterine contractions using a balloon inserted into its cavity; and 2) external hysterography - the study of uterine movements using devices placed on the woman's abdominal wall.
For internal hysterography, a current-dynamometer apparatus was proposed, which consists of a small rubber canister connected by a rubber tube to a T-shaped glass tube, to both ends of which two mercury manometers are attached. A float is placed in one of the manometers, ending with a pen for recording the curve of uterine contractions on a kymograph. The balloon is inserted into the uterus from the breast of the fetus and filled with water; the rest of the apparatus contains air. This instrument was used to study uterine contractions under the action of quinine, chloral hydrate, ether, and pituitrin. Methods of internal hysterography are now rarely used because of the risk of infection in the uterus.
Figure: Scheme of the apparatus for internal hysterography.
1 - uterine balloon filled with water; 2 - writing apparatus; 3 - water pumping device; 4 - kymograph.
External hysterography, which does not violate asepsis, has become widespread. Devices for external hysterography were originally based on the principle of air transmission using a rubber membrane acting on the Murray's tympanum. Uterine contractions were recorded on a kymograph. More advanced are devices without air transmission - hysterographs with direct recording; in them, the pressure of a spring applied to the abdominal wall is transferred to a writing stylet or pencil, and the recording is made on a long paper tape moving mechanically under the stylet.
Figure: Apparatus for external hysterography.
a - with air transmission; b - with direct recording.
SA Yagunov (1936) used external hysterography in the following way. On the stomach of the woman in labor, at the level of the navel, a cloth belt was superimposed, under which there is a rubber pad (6X20 cm). The latter is pneumatically connected by a rubber tube to the Murray drum. The recording of the curve can be made with the pen of Murray's drum or photographically using the Myasishchev apparatus. At the same time, contractions and attempts are transmitted pneumatically to the Murray drum, the vibration of which causes the movements of the mirror associated with it. A light beam from a mirror falls on a moving strip of photographic paper, on which an image of a curve is obtained. II Yakovlev used the method of recording its bioelectric currents to study uterine contractions. All such devices need improvement.
- What honey products. Beekeeping products. Royal jelly, beeswax, bee pollen. The power of nature on guard of health
- What does it really mean if a man says he's bored?
- Online fortune-telling on coffee grounds with the interpretation of signs Fortune-telling on desire on coffee grounds
- Sofia Kalcheva - about Nikolai Baskov: He dressed me in a mini, and I burned with shame Sofia Kalcheva now