Intensive care in obstetrics: An evidence-based review Parte II
Anaphylactoid syndrome of pregnancy (amniotic fluid embolus)
Amniotic fluid embolism is a rare but devastating complication of pregnancy that is characterized by acute onset of hypoxia, hypotension or cardiac arrest, and coagulopathy that occur during labor and delivery or within 30 minutes after delivery.113,114 This same constellation of findings may be caused by other causes such as hemorrhage, uterine rupture, or sepsis, each of which should be excluded before assignment of a diagnosis of amniotic fluid embolism. The combination of sudden cardiovascular and respiratory collapse with a coagulopathy is quite similar to that observed in patients with anaphylactic or septic shock. In each of these settings, a foreign substance (eg, endotoxin) is introduced into the circulation. This incites a cascade of events that result in the activation and release of mediators such as histamines, thromboxane and prostaglandins, which lead to disseminated coagulation, hypotension, and hypoxia. In this scenario, the inciting factor is presumed to be present in amniotic fluid that is introduced into the maternal circulation, yet the precise factors that initiate the sequence have yet to be identified. It is a commonly held misconception that the presence of fetal debris in the pulmonary circulation is diagnostic of an amniotic fluid embolus. In fact, fetal debris can be found in the pulmonary circulation in a predominance of normal laboring patients and is only identified in 78% of those patients who meet the criteria for the diagnosis of amniotic fluid embolism.113,114
Management of amniotic fluid embolism is entirely supportive. Replacement of blood and clotting factors, adequate hydration and blood pressure support, ventilatory support, and invasive cardiac monitoring in addition to resuscitation efforts are all generally required for these patients. Recent data suggest mortality rates approach >=61%. Most patients do not survive the initial course and die within 5 days. Of those patients who survive, neurologic impairment is common.113
Summary
Pregnant women may require intensive care because of complications of the pregnancy itself or as a result of nonobstetric conditions. In either setting, care of the critically ill pregnant woman requires knowledge of the primary disease process and its treatment in nonpregnant patients and a thorough understanding of maternal physiologic adaptations to pregnancy. Because there are frequently no data or literature that could guide intensive care of the pregnant patient, knowledge of maternal physiologic condition must be used to interpret and implement therapies that are studied only in nonpregnant patients. Thus, care should be provided by or in consultation with a maternal fetal medicine specialist or obstetrician who is thoroughly familiar with the management of high-risk pregnancies.
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