Postnatal hemostasis is a complex process that provides many factors: muscle, hemocoagulation, vascular and tissue, which contribute to the acceleration of thrombus formation due to the influence of amniotic fluid, placental extracts and other elements of the fetal egg on this process. From the point of view of the obstetric clinic, postpartum haemostasis provides two main factors: retraction of the myometrium, which leads to compression, twisting and involvement of the spiral uterine arteries (myogenic factor) and thrombus formation in the vessels of the placental site, promoted by clotting factors and accelerating tissue activators (hemocoagulation factor). Reliable hemostasis is achieved in 2-3 hours, when dense fibrinous thrombi associated with the wall of the vessels are formed. The formation of such thrombi significantly reduces the risk of bleeding with a decrease in the tone of the myometrium. In the first hours of thrombosis convolutions are soft, weakly associated with blood vessels, easily detached from the wall and washed away by blood flow during the development of hypotension.
Uterine bleeding in the early postpartum period is due to a violation of the contractile activity of the uterus, found in 2-2.5% of the total number of births.
Hypotonia of the uterus is the inadequate ability of the uterine wall to contract.
Atony of the uterus is a complete loss of the contractile activity of the uterus.
The causes of hypotension and atony are:
- Insufficiency of the neuromuscular apparatus of the uterus, which is associated with genetic factors, infantilism, ovarian hypofunction, insufficiency of hormones of the fetoplacental complex;
- Congenital diseases of the blood (thrombocytopenic purpura, etc )
- Morphological inferiority of the uterus (dystrophic cicatricial and inflammatory changes in myometrium associated with abortions, pathological births, tumors, surgical interventions)
- Overgrowth of the uterus (large fetus, polyhydramnios, multiple fetuses, narrow pelvis);
- Severe extragenital pathology, leading to disruption of homeostasis, vascular tone, endocrine balance;
- Hemostasis disorders associated with complications of pregnancy (fetal antenatal death and delay in the uterus, late gestosis, hemorrhagic shock, embolism with amniotic fluid);
- Placenta previa, premature detachment of the normally located placenta, tight attachment and increment of the placenta, retention in the uterus cavity afterparty or parts thereof;
- Weakness of labor or its discoordination, uncontrolled introduction of drugs (uterotonics), excessive pain, fatigue or arousal of a woman;
- Retention of the placenta or its parts in the uterine cavity.
The most favorable is the placement of the placenta in the body of the uterus. With its localization in the days and the lower segment, there is increased bleeding in labor. More frequent development of bleeding when placing the placenta in the uterus, due mainly to a violation of the myogenic factor of hemostasis. When the placenta is localized in the lower part of the uterus, hypercoagulation with increased consumption of internal factors of blood coagulation is observed, which leads to a violation of microcirculation, hemodynamics, development of "coagulopathy of consumption" and may cause increased blood loss.
With pathoanatomical and histological examination of the uterus removed in connection with hypotonic bleeding, significant leukocyte infiltration, foci of necrosis and dystrophy of muscle tissue, hemorrhage into the uterus are determined. Edema of the muscle fibers, swelling and loosening of connective tissue - are some of the characteristic changes that disrupt the contractile activity of the uterus. These changes can be a consequence of obstetric, extragenital pathology, prolonged and uncontrolled stimulation of uterotonics, which leads to blockade of the neuromuscular apparatus of the uterus, contributes to its atony and further aversion of drugs that stimulate uterine contractions.
The clinical picture of hypotonic bleeding consists of the following symptoms: bleeding from the uterus is impermanent, moderate or significant, with convolutions of blood. Uterus soft, shrinking very poorly, its dimensions increase due to the accumulation of convolutions of blood in its cavity. The spontaneous excitability of the uterus and its reaction to all kinds of irritations (pharmacological, chemical, thermal and mechanical) decrease.
In contrast to hypotonic bleeding, with injuries of the birth canal the uterus is dense. When examining the birth canal, ruptures of the cervix, vagina or perineum are diagnosed.
When atony, the uterus completely loses its spontaneous excitability and pharmacological reactivity. There comes the inhibitory phase of parabiosis in the nervous apparatus of the uterus.
The reasons for the transition of hypotension of the uterus into atony: irrational management of labor, gross manipulation, overdose of uterotonic drugs, continued hypoxemia, prolongation of the effect of hypotension of the uterus.
If untimely and inadequate treatment of the initial period of hypotension of the uterus, violation of its contractile function, the amount of blood loss increases. There are changes in the hemocoagulation system that indicate a significant use of coagulation factors, which leads to a decrease in the number of platelets and a decrease in the concentration of fibrinogen, the activity of factor VIII, prothrombin and thrombin time, while increasing fibrinolytic activity and the appearance of degradation products of fibrin and fibrinogen. All this contributes to the rapid progression of DIC syndrome.
The condition of the parturient woman depends on the intensity and volume of bleeding, the ascending state of the body, the stability of hemodynamics, the timeliness of the provision of qualified care. If untimely use of radical measures to stop bleeding, irreversible changes in vital organs quickly develop and the mothers die from acute hemorrhage and hemorrhagic shock.