Uterine atony

Uterine atony is a loss of uterine muscle tone. Normal uterine muscle contractions compress blood vessels and reduce the flow of advancing the clot and prevent bleeding.Uterine muscle failure leads to acute uterine bleeding. Clinical 80% of postpartum hemorrhage due to uterine atoniei.
Postpartum haemorrhage is the leading cause of maternal mortality. All women who carry a pregnancy over 20 weeks gestation are at risk of postpartum hemorrhage.Although maternal mortality has decreased more in developed countries, postpartum haemorrhage remains the leading cause of maternal mortality in the world.
Postpartum hemorrhage is defined as blood loss exceeding 500 ml after vaginal delivery or 1000 ml after cesarean. The loss of these amounts within 24 hours after birth is called primary or early postpartum hemorrhage, while bleeding after 24 hours of birth are secondary or delayed.
Side effects of hemorrhage depend postopartum individual capacities of the individual to compensate for the loss of blood. A healthy woman has a 30-50% increase in the volume of blood in a normal pregnancy, unique, and is more tolerant than a woman with anemia, bleeding, or dehydration cardiac pathological conditions, pre-eclampsia.
Atoniei diagnosis is usually reserved for uterine pregnancies have progressed over 20 weeks gestation. Births under 20 weeks are spontaneous abortions. Bleeding associated with spontaneous abortions may have common etiologies and therapies to those for uterine atony.
Frequency control is related atonii this stage three of labor. This is the period from birth until the child complete the removal of the placenta. Prevalence of postpartum hemorrhage of 500 ml is 5-13% and 1000 ml of about 1%.Increased frequency of bleeding in developing countries is reflected by the lack of availability of specific drugs and therapies. Lack of experience of doctors is also a risk factor. agents lack transfusion, anesthesia services and surgical interventional capabilities also play a role. Comorbidities mentioned above are mostly seen in developing countries and women combined led to decreased tolerance to hemorrhage.
Causes and risk factors:Postpartum hemorrhage has many possible causes, but the most common is uterine atony, the failure of the uterus to contract and retract after birth. Bleeding from a history of birth is a major risk factor. Other risk factors associated with uterine atoniei include birth weight, labor induction, chorioamnionitis, use of magnesium sulfate.
Uterine tone:Uterine atony and failure myometrium muscle contraction can lead to severe and rapid bleeding and hypovolemic shock. Supradistensia uterus, absolute or relative is a major risk factor for inertia. Supradistensia multifetala may be caused by pregnancy, fetal macrosomia, or fetal anomalies polihidraminos (hidrocefalus severe).
Myometrium contractions can result from fatigue due to weak labor intensive or rapid labor intensive, particularly if it stimulated. It can also be caused by inhibition of contractions by drugs such as halogenated anesthetic agents, nitrates, nonsteroidal anti-inflammatory, magnesium sulfate, nifedipine and beta-agonists.Other causes include placental implantation in the uterine lower segment, bacterial toxins (chorioamnionita, endomiometrita, septicemia), hypoxia due to rupture hipoperfuziei placenta or uterus Couvelaire resuscitation and hypothermia due to massive or prolonged uterine exteriorizarii. Recent studies show that multiparity is not an independent risk factor for postpartum hemorrhage.
Placental tissue:Uterine contractions and lead to detachment and retraction of the expelled placenta.And complete detachment of the placenta allows optimal retraction and occlusion of blood vessels.
Retention of a portion of the placenta is more common if the placenta has developed an accessory lobe. After elimination of the placenta and is present when minimal bleeding, the placenta should be inspected to emphasize that fetal vessels suggesting a lobe intrerupbrusc remember.The placenta is retained in an extreme burden pretermen (under 24 weeks), with massive bleeding. Recent studies show that use of misoprostol for pregnancy termination in second trimester of pregnancy leads to a low rate of retention of placenta compared with the technique that uses instilatiile uterine prostaglandin or hypertonic saline.
Failure to complete separation of the placenta occurs in the placenta accreta and its variants. In this condition the placenta has invaded over the cleavage plane and is normal in an abnormal adhesion. Significant bleeding occurred in the area where normal detachment may suggest placenta accreta. Placenta accreta may not lead to complete initial bleeding, but may develop if intensive efforts are made to remove the placenta. This condition should be considered when the placenta is implanted on the uterine scar, especially if associated with placenta previa.
Uterine Trauma:Genital tract lesions may occur spontaneously or by manipulation used to release the child. Caesarean birth cause a loss of blood two times higher than the vagina. Incisions in the lower uterine segment contractions weak heal well and are safer to suture, and hemostasis vasospasm.
Uterine rupture is common in patients with a history of cesarean birth. Routine transvaginal palpation of uterine scar is not recommended. Any uterus with a partial or total rupture of the wall should be considered a risk factor in future pregnancies.Interventions that increase the risk of bleeding include: fibroidectomia, uteroplastia congenital anomalies, ectopic cervical resection and uterine perforation with dilatation, curettage, biopsy, hysteroscopy or placement of intrauterine contraceptive devices.
Trauma can occur after a painstaking labor, especially if the patient had uterus stimulated with oxytocin or prostaglandins. The use of fetal monitoring may reduce the risk-loaded. Trauma can occur after handling enter or ectopic fetus. Risk associated with internal version and extraction of the second twin. Finally, secondary trauma can result in attempts to remove a retained placenta or manual instrumentation. The uterus should always be controlled with hands on abdomen during any such proceedings.
Cervical laceration associated with forceps application, and the cervix should be inspected after any such births. Vaginal delivery system (forceps or vacuum) should not be attempted without the cervix is ​​fully dilated. Cervical laceration can occur spontaneously. In these cases mothers were not able to withstand up to complete dilatation. Rare manual or instrumental exploration of the uterus can cause cervical lesions. Very rarely the cervix is ​​incised to facilitate delivrenta a fetal head blocked.Vaginal laceration is also very commonly associated with vaginal delivrenta interventional, but it may occur spontaneously, especially if hands are presented with fetal head. Lacerations can occur during handling in order to resolve a shoulder dystocia.
Thrombosis:In the immediate postpartum period, clotting disorders obizei not cause the excessive bleeding, uterine contractions and show the effectiveness of the retraction to prevent bleeding. Placental site storage and fibrin clots in blood vessels play an important role in the hours and days following birth.Abnormalities of this process can be gained or defects. Thrombocytopenia may be associated with preexisting disease such as idiopathic thrombocytopenic purpura and HELLP syndrome secondary. Rarely platelet functional abnormalities may occur. Many of these are legacy, although sometimes they are undiagnosed.
Preexisting abnormalities of the coagulation system, such as family and hypofibrinogenemia Willebrand disease may occur. A bleeding disorder should be suspected in a woman with bruises without known trauma, gastrointestinal tract bleeding without obvious injury or epistaxis than 10 minutes duration.
Risk factors and conditions associated with atonic uterus may be missing in many women. Different etiologies may have risk factors, which is especially true in uterine atony or trauma. Postpartum hemorrhage is usually a single cause, but more than one case is also possible, especially after a prolonged labor ending by assisted vaginal delivery.
The mechanism of bleeding:During pregnancy maternal blood volume increases by 50% (from 4 to 6 L). plasma volume increases above the concentration of figurative elements, leading to loss of hemoglobin and hematocrit values. Increased blood serves to ensure strong demand for infusion of uteroplacental unit and to bring the amount of blood that will be lost at birth.The estimated blood flow within the uterus is 500-800 ml / min accounted for 10-15% of cardiac output. Most of this flow passes through the low resistance placental bed.Uterine blood vessels that provide fiber intake crosses placental myometrium. As these fibers contract retraction occurs after birth. Retraction is the only feature of the uterine muscle to maintain its normal length after each contraction. Blood vessels are compressed and blood flow stopped. This phenomenon is called "physiological sutures.