Chapter 197 Amniotic Fluid Embolism
INTRODUCTION
Description: Amniotic fluid embolism is a rare but frequently fatal complication of labor in which amniotic fluid containing fetal squamous cells and hair enters the maternal vascular system and becomes lodged in the pulmonary vascular bed. Mechanical obstruction and anaphylaxis combine to produce an often-fatal clinical course. The term “anaphylactoid syndrome of pregnancy” has been suggested but has not received wide acceptance.
ETIOLOGY AND PATHOGENESIS
DIAGNOSTIC APPROACH
Workup and Evaluation
Laboratory: Coagulation studies, blood gas measurements, renal function studies, all on an ongoing basis.
Imaging: May help in managing pulmonary complications but generally not helpful in establishing the diagnosis.
MANAGEMENT AND THERAPY
Nonpharmacologic
General Measures: Aggressive airway control and cardiovascular resuscitation (including myocardial support, inotropic agents and fluids, high-concentration oxygen therapy). The use of vasopressors has been reported to be successful. Correction and support for clotting defects (blood and platelets, fresh-frozen plasma, and cryoprecipitate as indicated).
FOLLOW-UP
Patient Monitoring: Intensive hemodynamic monitoring required. Laboratory testing in anticipation of coagulopathy.
Possible Complications: Acute mortality rates with amniotic fluid embolism approximate 50%. Of women who survive, 50% have a life-threatening bleeding diathesis. Renal failure is common, as are pulmonary edema and adult respiratory distress syndrome. Of women who suffer cardiac arrest during the initial phase, only 8% survive neurologically intact. Overall maternal mortality approaches 80%. More than half of the neonates that survive have neurologic impairment.
MISCELLANEOUS
Other Notes: The most devastating effects of amniotic fluid embolism appear to be mediated through the anaphylactic reaction induced. Experimental studies indicate that pretreatment with inhibitors of leukotriene synthesis can prevent the development of symptoms in experimental settings.
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