Intrauterine pressure of the human uterus. Amniotic fluid embolism

Childbirth ( partus) - the process of expulsion of the fetus from the uterus after the fetus reaches viability.

In the Russian Federation, since 2005, childbirth is considered the birth of a child weighing 1000 g or more at 28 weeks of gestation or more. According to the WHO recommendation, childbirth is considered to be the birth of a fetus starting at 22 weeks of gestation (weight 500 g or more). In our country, termination of pregnancy between 22 and 28 weeks is considered an abortion. All the necessary medical and resuscitation measures are taken for those born alive during these gestational periods. If the child goes through the perinatal period (168 hours), then a medical birth certificate is issued and the newborn is registered at the registry office, and the mother receives a certificate of incapacity for work for pregnancy and childbirth.

In addition to spontaneous, induced and programmed childbirth are distinguished. Induced childbirth includes artificial birth according to indications from the mother or fetus.

Programmed labor - artificial birth at a time of day convenient for the doctor.

Reasons for onset of labor

The reasons for the onset of labor have not yet been established. Childbirth is a complex multi-link process that arises and ends as a result of the interaction of the nervous, humoral and fetoplacental systems, which affect the contraction of the muscles of the uterus. Contractions of the muscles of the uterus do not differ from the contraction of smooth muscle muscles in other organs and are regulated by the nervous and humoral systems.

By the end of pregnancy, as a result of fetal maturity and genetically determined processes against this background, both in the mother's body and in the fetal-placental complex, relationships are formed aimed at strengthening the mechanisms that activate the contraction of the uterine muscles.

The activating mechanisms include, first of all, the enhancement of nerve stimuli arising in the ganglia of the peripheral nervous system, the connection of which with the central nervous system is carried out through the sympathetic and parasympathetic nerves. Adrenergic receptors a and b are located in the body of the uterus, and m-cholinergic receptors are located in the circular fibers of the uterus and the lower segment, where serotonin and histamine receptors are simultaneously located. The excitability of the peripheral parts of the nervous system and after this subcortical structures (amygdala nuclei of the limbic part of the hypothalamus, pituitary, pineal gland) increases against the background of inhibition in the cerebral cortex (in the temporal lobes of the cerebral hemispheres). This relationship promotes the automatic reflex contraction of the uterus.

The second variant of the mechanisms that activate uterine contractions, closely related to the first, is humoral. Before childbirth, the content of compounds in the blood of a pregnant woman increases, leading to an increase in the activity of myocytes: estriol, melatonin, prostaglandins, oxytocin, serotonin, norepinephrine, acetylcholine.

The main hormone responsible for preparing the uterus for childbirth is estriol... Cortisol and melatonin, synthesized in the fetus, play a special role in increasing its level. Cortisol serves as a precursor and stimulant of estriol synthesis in the placenta. Estrogens help prepare the uterus and the mother's body as a whole for labor. In this case, the following processes occur in the myometrium:

Increase in blood flow, synthesis of actin and myosin, energy compounds (ATP, glycogen);

Intensification of redox processes;

Increasing the permeability of cell membranes for potassium, sodium, especially calcium ions, which leads to a decrease in the membrane potential and, consequently, an acceleration of the conduction of nerve impulses;

Suppression of oxytocinase activity and preservation of endogenous oxytocin, which reduces cholinesterase activity, which contributes to the accumulation of free acetylcholine;

An increase in the activity of phospholipases and the rate of the "arachidonic cascade" with an increase in the synthesis of PGE in the amniotic and PGF2a in the decidua.

Estrogens increase the energy potential of the uterus, preparing it for long-term contraction. At the same time, estrogens, causing structural changes in the cervix, contribute to its maturation.

Before childbirth, the uterus becomes estrogen-dominant with a predominance of the activity of a-adrenergic receptors and a decrease in b-adrenergic receptors.

An important place in the initiation of labor activity belongs melatonin, the concentration of which increases in the fetus, and decreases in the mother. A decrease in the level of melatonin in the mother's blood promotes the expression of foli- and lutropin, leading to the activation of estrogen synthesis. Melatonin not only enhances estrogen function, but also activates immune responses by suppressing the synthesis of immunosuppressants prolactin and hCG. This, in turn, enhances the transplant immunity and stimulates the rejection of the fetus as an allograft.

For the onset of labor and contraction of the muscles of the uterus are important PGE and PGF 2a - direct labor activators. The first of them to a large extent contributes to the maturation of the cervix and uterine contraction in the latent phase, and PGF2a - in the latent and active phase of the first stage of labor.

An increase in the synthesis of prostaglandins is due to the activation of the "arachidonic cascade" before childbirth as a result of degenerative changes in the decidual, fetal membranes, placenta, as well as the release of fetal cortisol and an increase in estriol.

Prostaglandins are responsible for:

Formation on the muscle membrane of a-adrenergic receptors and receptors for oxytocin, acetylcholine, serotonin;

An increase in the level of oxytocin in the blood due to inhibition of the production of oxytocinase;

Stimulation of the production of catecholamines (adrenaline and norepinephrine);

Providing automatic contraction of the muscles of the uterus;

Deposition of calcium in the sarcoplasmic reticulum, which contributes to prolonged contraction of the uterus during childbirth.

One of the important regulators of the contractile activity of the uterus is oxytocin secreted in the hypothalamus and secreted before childbirth by the pituitary gland of both the mother and the fetus.

The sensitivity of the uterus to oxytocin increases in the last weeks of pregnancy and reaches a maximum in the active phase of the first period, in the second and third stages of labor. By increasing the tone of the uterus, oxytocin stimulates the frequency and amplitude of contractions by:

Excitation of a-adrenergic receptors;

Reducing the resting potential of the cell membrane and thereby the irritability threshold, which increases the excitability of the muscle cell;

Synergistic action on acetylcholine, which increases the rate of its binding to myometrium receptors and release from the bound state;

Inhibition of cholinesterase activity, and, consequently, the accumulation of acetylcholine.

Along with the main uterotonic compounds in the preparation for childbirth, an important role belongs to serotonin, which also inhibits the activity of cholinesterase and enhances the action of acetylcholine, promoting the transfer of excitation from the motor nerve to the muscle fiber.

The change in the ratio of hormones and biologically active substances affecting the excitability and contractile activity of the uterus before childbirth takes place in several stages: the first stage is the maturity of the hormonal regulation of the fetus (cortisol, melatonin); the second stage is the expression of estrogen and metabolic changes in the uterus; third stage -

synthesis of uterotonic compounds, primarily prostaglandins, oxytocin, serotonin, which ensure the development of labor. The processes occurring before childbirth in the central and peripheral nervous system, endocrine system and fetoplacental complex are combined into the concept of "generic dominant".

In childbirth, alternating excitation of the centers of sympathetic and parasympathetic innervation develops. Due to the excitation of the sympathetic nervous system (norepinephrine and adrenaline) and the release of mediators, the longitudinally located muscle bundles in the body of the uterus contract with simultaneous active relaxation of the circularly (transversely) located bundles in the lower segment. In response to the maximum excitation of the center of the sympathetic nervous system and the release of a large amount of norepinephrine, the center of the parasympathetic nervous system is excited, under the action of the mediators of which (acetylcholine) the circular muscles contract while the longitudinal muscles are relaxed; after reaching the maximum contraction of the circular muscles, the maximum relaxation of the longitudinal muscles occurs. After each contraction of the uterus, its complete relaxation occurs (a pause between contractions), when the synthesis of contractile proteins of the myometrium is restored.

For internal fetal cardiotocography, which is an invasive study, for direct recording of the fetal heart rate, the electrode is attached directly to the fetal scalp. Using a catheter inserted into the uterine cavity, the frequency of uterine contractions and intrauterine pressure are measured. Intrauterine registration is carried out only during childbirth after rupture of the membranes and dilatation of the cervix by 3 cm, when the degree of insertion of the fetal head is -2 and only under the condition that external cardiotocography gives inaccurate data. Internal cardiotocography allows you to obtain more accurate information about the condition of the fetus than external, and is especially indicated in cases where it is necessary to find out whether to resort to a caesarean section. The study is associated with minimal risk for the mother (perforation of the uterus and infection of its cavity) and the fetus (formation of hematoma and abscess of the scalp).

Target

• Monitoring fetal heart rate, especially its variability.
• Determination of the frequency and strength of uterine contractions to assess the dynamics of labor.
• Assessment of the condition of the fetus during childbirth.
• Supplementing or replacing external cardiotocography.

Preparation

• It should be explained to the patient that the study will provide reliable information about the state of the fetus and the contractile function of the uterus and that its conduct does not mean that she has serious disturbances in labor or the condition of the fetus. It is necessary to describe the essence of the research and answer the patient's questions.
• The patient should be warned about the possibility of discomfort when the catheter is inserted into the uterine cavity or when the electrode is attached to the fetal scalp.
• It is necessary to ensure that the patient or her family gives written consent to the study.

Equipment

Sterile electrode for attachment to the fetal scalp and guide tube, catheter for measuring intrauterine pressure, catheter guide, pressure transducer, cardiac monitor.

Procedure and follow-up care

Measuring heart rate

• The patient is positioned as in stone cutting, the perineal area is prepared as for a vaginal examination, and each manipulation performed by a doctor or a specially trained nurse is explained. At the beginning of the study, the patient is asked to breathe through the mouth and relax the abdominal muscles.
• After vaginal examination, the fetal scalp is palpated and a suitable place is selected on it. A plastic tube with a thin electrode is inserted into the cervical canal, pressed against the scalp, and rotated clockwise to attach the electrode. With a slight twitching of the electrode, the firmness of the fixation is confirmed and the tube is removed.
• The plate electrode is moistened with an electrolyte solution and attached to the patient's thigh. An electric cable is attached to the electrode, which is connected to the heart monitor. To check the correct placement of the electrode on the fetal scalp, the cardiac monitor is turned on, and a heart rate signal should appear.

Measuring the frequency and strength of uterine contractions

• Before inserting the uterine catheter, it is filled with sterile 0.9% sodium chloride solution to prevent air embolism. Each step of the procedure should be explained to the patient.
• The patient is asked to breathe through the mouth and relax the abdominal muscles.
• After conducting a vaginal examination and determining the presenting part of the fetus, the catheter together with the guidewire is inserted through the cervical canal 1-2 cm (usually between the head of the fetus and the posterior wall of the cervix). The catheter is then gently advanced into the uterine cavity until the black mark is flush with the vulva (the catheter guide cannot be inserted deep into the uterine cavity). The guidewire is removed and the catheter is connected to a transducer that converts the intrauterine pressure transmitted by the fluid in the catheter into an electrical signal.

In both dimensions

• After removing the electrode from the scalp of the fetus, an antiseptic or antibiotic solution is applied to the electrode site.
• After childbirth, the patient and the baby should be closely monitored due to the possibility of developing endometritis and an abscess of the baby's scalp.

Precautionary measures

• Internal cardiotocography of the fetus is contraindicated if the exact presentation of the fetus is not known, and the application of the electrode to the scalp of the fetus is associated with technical difficulties.
• To avoid artifacts when registering intrauterine pressure, the pressure sensor should be rinsed with 0.9% sodium chloride solution, and to prevent clogging of the catheter, for example, cheese grease, a little 0.9% sodium chloride solution should be poured into it, disconnecting it from the recording system.
• If your heart rate is low, you should make sure that this is the fetal heart rate, not the mother's.
• If the nature of the change in heart rate indicates fetal hypoxia, measures should be taken to eliminate it: turn the mother on her side, preferably the left one, which will slightly increase

BP, inject intravenous fluids to improve placental blood circulation, give oxygen to breathe. If, after these measures, the fetal heart rate is normalized, the birth can be continued, otherwise it is advisable to resort to a cesarean section.

The intrauterine catheter and ECG electrode should be removed before performing a cesarean section.

Normal values

Normally, fetal heart rate ranges from 120 to 160 beats / min with variability from 5 to 25 per minute (see Normal indicators of frequency and strength of uterine contractions).

Deviation from the norm

Bradycardia (heart rate less than 120 beats / min) may be the result of fetal conduction disturbances, its incorrect position in the uterus and hypoxia, as well as the mother's intake of certain drugs, such as propranolol and narcotic analgesics.

Tachycardia (heart rate more than 160 beats / min) can occur as a result of early fetal hypoxia, arrhythmias and infectious complications, prematurity, maternal fever, as well as tachycardia, hyperthyroidism and anticholinergic drugs.

A decrease in rhythm variability (deviation from the basal heart rate by less than 5 beats / min) may be a consequence of arrhythmia and conduction disturbances in the fetus, as well as hypoxia, disorders of the nervous system, infectious complications, as well as the mother's intake of narcotic and anticholinergic drugs. Early decelerations (a decrease in heart rate at the beginning of uterine contraction, followed by a return to the initial level within no more than 15 seconds after the end of the contraction) are associated with compression of the fetal head and usually indicate the well-being of the fetus. Late decelerations (a decrease in heart rate after the onset of uterine contraction, followed by recovery for more than 15 s after a delay period of more than 20 s) are the result of placental insufficiency, fetal hypoxia or acidosis. Recurrent late decelerations with reduced heart rate variability usually indicate serious fetal distress, which may be caused by conduction anesthesia (spinal, caudal, or epidural) or fetal hypoxia.

The changeable nature of deceleration (a sudden sharp decrease in heart rate, not associated with uterine contractions) is usually caused by compression of the umbilical cord. A pronounced decrease in heart rate (less than 70 beats / min for more than 60 s) with a decrease in variability indicates that the fetus is not well and a greater likelihood of various disorders in the newborn. Insufficiently expressed variability without periodicity is an unfavorable sign and requires additional research, in particular, studies of fetal blood gases.

Reduced intrauterine pressure during childbirth, which does not continue to decrease further, requires stimulation of labor with oxytocin. Increased intrauterine pressure indicates placental abruption or oxytocin overdose, which can cause impaired placental circulation and cause fetal hypoxia.

Factors influencing the research result

Drugs acting on the parasympathetic and sympathetic nervous system.

B.H. Titova

"Internal cardiotocography of the fetus" and other articles from the section

Subject table of contents "Registration of uterine contractile activity. Hysterography. Cardiotocography (CTG).":
1. Registration of uterine contractile activity. External hysterography. Multichannel external hysterography. Hasin's formula.
2. Internal hysterography (tocography). Registration (measurement) of intrauterine pressure. Units of Montevideo.
3. Radio telemetry. Cardiotocographs.
4. Intranatal cardiotocography. Indications for intrapartum cardiotocography (CTG).
5. Evaluation of data of cardiotocography (CTG). Basal rhythm. Normal basal rhythm. Basal rate. Fetal heart rate variability.
6. Oscillations. Normal oscillation amplitude. Undulating curve type. Oscillation variability.
7. Acceleration. Sportive, periodic acceleration. Deceleration. Sportive, periodic deceleration.
8. Classification of decelerations. Early, late and variable decelerations.
9. Atypical variable deceleration. Deceleration amplitude. Assessment of uterine activity.
10. Decoding of cardiotocography (CTG). Clinical evaluation of cardiotocography data (CTG). Saltatory rhythm of fetal heart contractions.
11. Sinusoidal rhythm of fetal heart contractions. Krebs scale. Krebs estimate. Krebs points. Zaling's test.
12. Algorithm of labor management in violation of fetal cardiac activity.

Internal hysterography (tocography). Registration (measurement) of intrauterine pressure. Units of Montevideo.

With internal tocography(the sensor is in the uterine cavity) register intrauterine pressure outside and during the fight, which indirectly, but quite accurately allows you to judge the features of the contractile activity of the uterus.

The first intrauterine tocography applied in 1871 by F. Schatz, which introduced a gutta-percha balloon with a diameter of 3 cm into the uterine cavity and recorded. Subsequently, many studies appeared aimed at improving internal hpsterography.

For registration of intrauterine pressure the most widespread is the iptraamnial introduction of an open catheter through the cervical canal. Less often, balloons of various diameters were introduced into the uterine cavity for tocography. Extraamnial placement of an open catheter and balloons due to the lack of accuracy and danger of the method is currently practically not used.

Rice. 6. Multichannel internal hysterography (diagram).

The fundamental research of R. Caldeyro-Barciaefal deserves special attention. (1960), who, in order to study the contractile activity of the uterus in a transabdominal way, introduced an open catheter into the uterine cavity and micro balloons with a capacity of 0.02 ml into the myometrium of various parts of the uterus (fundus, body, lower segment). This allowed the authors to study in detail the appearance and propagation of the contraction wave, the tone of the uterus, the amplitude and duration of contractions, the interval between contractions, etc. They were able to scientifically confirm the concepts " triple downward gradient" and " fundus dominant"(Fig. 6), to identify various forms of discoordination of labor, to propose a method for assessing uterine activity in units of Montevideo.

Due to the danger and non-physiological this registration method is not widespread in practical obstetrics, although its scientific value is enormous.

All modern foreign cardiotocographs, in addition to the external sensor, have devices for recording intrauterine pressure.

Intrauterine (amniotic) pressure is the result of the contractile activity of various parts of the uterus; registration of its value will make it possible to judge the activity of the organ as a whole. The presence of good coordination between different parts of the uterus is proved by the fact that during uterine contractions, the amniotic pressure recording curve has a regular sinusoidal shape. Synchronous relaxation of all parts of the uterus during normal childbirth leads to a smooth decrease in amniotic pressure to the level of normal tone outside the contraction.

At discoordination of labor hysterographic curve takes on an irregular shape during the increase in pressure or its decrease, or throughout all the contractions. With weakness of labor, contractions are rare, of low intensity and duration,

Internal tocography methods favorably differ from methods of external hysterography, since they can be used to obtain reliable data during and outside contractions in certain units of measurement (mmHg), as well as a more accurate description of the duration of contractions in time. However, these methods have some disadvantages (forced position of the woman in labor, the risk of infection and premature opening of the fetal bladder).

Embolism with amniotic fluid is a condition that occurs during pregnancy when elements of fetal fluid enter the mother's bloodstream and is accompanied by the development of acute heart and lung failure or circulatory arrest.

Such a complication is possible when the pressure in the amnion rises higher than in the blood vessels of the uterus or the gaping of the venous vessels of the uterus.

Reasons that increase intrauterine pressure:

• - Excessive labor activity;
• - Fast delivery;
• - The use of large doses of oxytocin;
• - Polyhydramnios;
• - Large fruit;
• - Multiple pregnancy;
• - Breech presentation;
• - Dystocia of the cervix;
• - Postterm pregnancy;
• - Delayed rupture of the fetal bladder;
• - Rough manipulations during childbirth (Kristellerat's reception).

The reasons causing the 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.

The clinical picture of amniotic fluid embolism depends on the volume and composition of the waters that have entered the mother's blood vessels.

Diagnosis of amniotic fluid embolism is based on the assessment of clinical symptoms, laboratory examination and additional research methods.

Amniotic fluid embolism symptoms:

• - Chills;
• - Cough;
• - Pallor or cyanosis;
• - in the chest;
• - Shortness of breath;
• - Decrease in 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.

- X-ray changes are detected immediately or several hours after embolism and are characterized by a picture of interstitial drainage pneumonitis.

Differential diagnosis of amniotic fluid embolism is carried out with the following pathology:

- Myocardial infarction - pain, radiating to the left arm, rhythm disturbances, changes on the ECG, are 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) the right g, on the ECG;

- Air embolism (in case of gross violation of the infusion technique);

- Mendelssohn's syndrome (bronchospasm in response to acidic stomach contents entering the upper respiratory tract) - acid-aspiration hyperergic pneumonitis. It happens, as a rule, on induction of 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 advice, vascular.

Therapeutic tactics for amniotic fluid embolism:

1.During pregnancy - urgent delivery.

2.Treatment of cardiopulmonary shock or cardiopulmonary
resuscitation.

3.Correction of coagulopathy.

4. Surgical intervention for bleeding.

Priority measures for:

1. In case of circulatory arrest - CPR.

2. With increasing signs of respiratory failure - intubation of the trachea and mechanical ventilation with 100% oxygen with PEEP + 5 cm of water Art.

3.Puncture and catheterization of the subclavian or internal jugular vein with CVP control. Taking 5 ml of blood for coagulogram and examination for the presence of elements of amniotic fluid.

4. Catheterization of the bladder with an indwelling catheter.

Vital signs monitoring should include:

- Measurement of blood pressure every 15 minutes;
-CVD;
- heart rate;
-BH;
- Pulse oximetry;
-ECG;
-Hourly diuresis and general urine analysis;
- Thermometry;
- X-ray of the chest cavity organs;
-; platelets;
- Coagulogram;
- Acid-base state and blood gases;
- Biochemical blood test 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 H2O Art. inotropic support is carried out: dopamine (5-10 μg / kg / min) or dobutamine (5-25 μg / kg / min.). Isotropic therapy is started with minimal doses, and if there is no effect, they are gradually increased. It is desirable 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. Fighting coagulopathy (according to the protocol for the treatment of disseminated intravascular coagulation).

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 urine output> 30 ml / hour;
• - Normalization of hemostasis indicators;
• - Reduction of signs of respiratory distress.

Criteria for stopping mechanical ventilation:

• - Stabilization of the patient's clinical condition;
• - Respiratory rate less than 30 per minute;
• - Inspiratory effort less than -15 cm of water. Art .;
• - PaO2 / PiO2> 80 mm Hg. Art. / 0.4 at PEEP 7 cm of water. Art .;
• -. The patient's ability to independently double the volume of exhaled air per minute.

The article was prepared and edited by: surgeon