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Amniotic fluid embolus: Dx

Epidemiology: rare (1:20,000 deliveries) but potentially lethal complication (86% mortality rate in some series)

Time Frame: Amniotic fluid embolism can occur during labor, delivery, cesarean section, or postpartum.

Mortality: Exceeds 50% in the first hour.

Etiology: Entry of amniotic fluid into the maternal circulation through any break in the uteroplacental membranes. These breaks may occur during normal delivery or cesarean section or following placental abruption, placenta previa, or uterine rupture. In addition to desquamated fetal debris, amniotic fluid contains various prostaglandin and leukotrienes, which appear to play an important role in the genesis of this syndrome. The alternate term “anaphylactoid syndrome of pregnancy” has been suggested to emphasize the role of chemical mediators in this syndrome.

Symptoms: Typically, patients will present with sudden tachypnea, cyanosis, shock, and generalized bleeding. Three major pathophysiological manifestations are responsible: (1) acute pulmonary embolism, (2) DIC, and (3) uterine atony. Seizures and pulmonary edema may develop; the latter has both cardiogenic and noncardiogenic components. Acute left ventricular dysfunction appears to be a common feature.

Diagnosis: Sudden respiratory distress and circulatory collapse should cause you to strongly consider amniotic fluid embolism. However, it may also initially mimic acute pulmonary thromboembolism, venous air embolism, overwhelming septicemia, or hepatic rupture or cerebral hemorrhage in a patient with toxemia.

The diagnosis can be firmly established only by demonstrating fetal elements in the maternal circulation (usually at autopsy or less commonly by aspirating amniotic fluid from a central venous catheter

Treatment: consists of aggressive cardiopulmonary resuscitation, stabilization, and supportive care. When cardiac arrest occurs prior to delivery of the fetus, the efficacy of closed-chest compressions appears to be marginal at best. Aortocaval compression impairs resuscitation in the supine position, whereas chest compressions are less effective in a lateral tilt position. Moreover, expeditious delivery appears to improve maternal and fetal outcome; immediate (cesarean) delivery should therefore be carried out. Once the patient is resuscitated, stabilization with mechanical ventilation, fluids, and inotropes is best carried out with full invasive hemodynamic monitoring.