Uterine atony is a complete loss of uterine tone in the subsequent or early postpartum period. Insufficiency of contractile function leads to a violation of hemostasis and massive bleeding. A woman in labor has symptoms of shock, blood pressure decreases, and DIC syndrome may develop. Diagnosis is carried out according to clinical manifestations. Treatment is aimed at eliminating the cause of atony. At an early stage, the uterine cavity is examined to remove the remnants of the afterbirth, conservative methods of restoring tone are used. In case of inefficiency, surgical methods of treatment are resorted to.
O62.2 Other types of weakness of labor activity. Uterine atony
Uterine atony (Greek “a” – negation, “tonos” – tension) in modern obstetrics refers to rare complications of childbirth and the postpartum period. Unlike hypotension, which is the cause of bleeding in 90% of cases, a complete lack of tone is observed in 4-6% of women in labor with complications in the first hours after childbirth. Pathology develops more often in adolescents and very young patients or in women in labor of late reproductive age. The risk of atonia is higher in women who have become more expensive, as well as in patients with gynecological diseases.
A decrease in uterine tone may occur after previous hypotension (secondary atony) or without prior contractility disorders (primary or true atony). With true pathology, its cause is considered to be congenital inferiority of the myometrium, improper mutual influence of neurohumoral mechanisms, a change in the ratio of acetylcholine, cholinesterase and sex steroids. The following factors predispose to the development of atonia on the background of hypotension:
- Overgrowth of the myometrium. With multiple pregnancies, polyhydramnios or the birth of a large fetus, muscle tissues stretch, their ability to contract worsens. In women in labor with a high parity of labor, with a small interval between pregnancies, the probability of atony is higher.
- Delay of parts of the afterbirth. The increment or tight attachment of the placenta, the remnants of the fetal membranes do not allow the uterus to contract in order to stop bleeding. Atonia occurs with a large placental site located in the area of the uterine fundus.
- Violation of labor activity. Rapid childbirth causes overexcitation of the nervous system and quickly depletes it. With prolonged contractions, secondary birth weakness and forced prolonged stimulation with oxytocin, neuromuscular transmission is also disrupted and atony occurs.
- Morphological changes of the myometrium. The ability of the uterus to contract is reduced by scarring after a previous cesarean section or surgical interventions. The risk increases in women in labor with fibroids, endometritis and a large number of abortions in the anamnesis.
- Injury of the uterus. With hypotension, the doctor may resort to external uterine massage, less often in case of violation of the separation of the placenta, it is pulled by the umbilical cord. This damages the myometrium and leads to loss of contractility.
Normally, bleeding after separation of the placenta stops as a result of contraction of the myometrium, which increases the tortuosity of the spiral arteries, narrows their lumen. Activation of blood clotting factors leads to the formation of blood clots. But with prolonged labor, overgrowth of the uterus, ATP reserves are depleted, humoral regulation is disrupted.
First, hypotension occurs, the myometrium can react to external stimuli, the introduction of uterotonics. If blood clots, remnants of the placenta or fetal membranes remain in the uterine cavity, they do not allow the uterus to contract and support bleeding. With blood loss of 500 ml or more, hemostasis disorders develop, the reserves of the blood coagulation system are depleted. This leads to hemorrhagic shock, dysfunction of internal organs, DIC syndrome and death.
Signs of a decrease in uterine tone are diagnosed in the 3rd period of labor or after the release of the afterbirth. Normally, small painful contractions of the myometrium are preserved at this stage, but they are absent with atony. A large amount of blood or clots is released from the vagina. Sometimes the uterine cavity is able to deposit up to 1 liter of blood, while there are no noticeable symptoms of deterioration. Pressing on the bottom of the uterus increases bleeding. Worries about severe chills, tachycardia, shortness of breath.
With atony, continuous and profuse bleeding causes hemorrhagic shock. The skin turns pale, the woman in labor feels an increased heartbeat, dizziness. Symptoms of shock increase, blood pressure drops. In the absence of timely help, the patient loses consciousness.
The risk of severe complications of atonia is higher in women in labor who were diagnosed with gestosis or preeclampsia during pregnancy. In these conditions, a state of hypercoagulation is observed, therefore, with uterine atony, even a small bleeding can lead to a breakdown of compensatory mechanisms and the development of DIC syndrome. In pregnant women with obesity, the increase in CBV during pregnancy is less, minimal blood loss threatens hemorrhagic shock.
A fatal outcome can occur with massive or small bleeding, the probability depends on the compensatory abilities of the body. A marked decrease in CBV leads to a decrease in venous return to the heart, a decrease in minute and stroke volume, blood pressure and death.
With uterine atony, the speed of diagnosis of the condition and determination of the degree of blood loss is crucial. This allows you to start treatment as early as possible and improve the prognosis. An anesthesiologist-resuscitator is connected to the examination of the woman in labor. The following methods and techniques are used:
- External inspection. With hypotension, a flabby, soft uterus is palpated. After the development of atony, palpation through the abdominal wall is difficult, sometimes the bottom of the uterus is felt under the xiphoid process.
- Examination of the birth canal. When the hand is inserted into the uterine cavity, the doctor does not feel its contraction in response to irritation. Sometimes it is possible to separate blood clots or remnants of placental tissue that caused hypotension.
- Assessment of blood loss. The volume of blood released into the tray after childbirth is measured, the severity of bleeding is determined by hematocrit, hemoglobin level or Algover index.
In the postpartum period, a woman remains in the delivery room, but in severe cases, when surgical care is needed, she is transferred to the operating room. Emergency medical care is provided by an obstetrician-gynecologist together with an anesthesiologist and a transfusiologist. Treatment is carried out from the simplest methods to the most complex, if the chosen method of treatment is ineffective, it is dangerous to reuse it.
When the first signs of a decrease in uterine tone appear, methods are used to quickly cause a contraction of the myometrium and vascular spasm. But with pronounced atony, which developed without previous hypotension, some stages are skipped and move on to more active actions. The main methods of treatment are as follows:
- Cooling. Immediately after the appearance of the afterbirth, a heating pad with ice is placed on the lower abdomen. This helps to reduce blood flow to the uterus, increase myometrial spasm and stop bleeding.
- Introduction of uterotonics. The method is effective in the case of atony, if during childbirth the drugs were not administered in excess and did not cause hyperstimulation of the uterus. After the birth of the afterbirth, oxytocin or methylergometrine is prescribed in a jet.
- Manual separation of the placenta. If the cause of atony is the delay of parts of the afterbirth, the patient is given anesthesia and the uterine cavity is examined with simultaneous removal of parts of the placenta and fetal membranes.
- Massage of the uterus. It can be carried out through the anterior abdominal wall, the uterine floor is bent forward and anteriorly. At this stage, blood loss may stop. If the impact through the abdomen is ineffective, an external-internal massage is performed.
- Prostaglandin injections. A solution of prostaglandins is injected into the uterine wall, which stimulate uterine contraction. The method is used with a volume of blood loss of no more than 1500 ml.
- Correction of hemostasis. Plasma preparations are administered to compensate for blood clotting disorders and prevent severe complications. Aminocaproic acid preparations, water-salt and colloidal solutions are also used.
- Tamponade of the uterus. A hemostatic intrauterine balloon is inserted into the cavity. It is filled with 300-400 ml of sodium chloride solution. Outside there is a tank, the filling of which is judged on the tone.
If conservative treatment of uterine atony is ineffective, surgical care is provided. The obstetrician-gynecologist chooses the method of treatment individually, based on the condition of the woman in labor and the amount of blood loss. Sometimes balloon tamponade is performed as a preliminary stage before surgical treatment of atonia, which allows you to delay the start of the operation and carefully prepare. The following techniques are effective:
- Hemostatic sutures. Laparotomy is performed, compression of the uterus is achieved using a B-Linch, Hayman, Cho or Pereiro suture. Absorbable suture material is used, which does not need to be removed.
- Ligation of the internal iliac arteries. After opening the abdominal cavity, the iliac arteries are squeezed, but if there is no access to them, the uterine arteries can be ligated. In the presence of equipment, obese patients are shown embolization of blood vessels.
- Hysterectomy. The operation is performed while maintaining atony and continuing bleeding. Appendages are not removed at the same time.
Prognosis and prevention
The prognosis for a woman in labor with uterine atony depends on the accuracy of diagnosis and the start time of treatment. With insufficient compensatory capabilities of the body, a fatal outcome is possible with a little bleeding. Prevention consists in the proper management of the second period of labor, careful separation of the placenta and moderate use of uterotonics.
To reduce the risk of atonia, patients planning to conceive and pregnant women need to control their weight and blood pressure in order to prevent the development of gestosis. Between childbirth, it is necessary to take a break for at least 2 years, refuse abortions and treat inflammatory diseases of the pelvic organs in a timely manner. If you have a cesarean section, it is not recommended to get pregnant for 2.5-3 years, before conception you should undergo an examination.