Chapter 8: Amniotic Fluid Embolism

BACKGROUND

Amniotic fluid embolism (AFE) incidence is very rare (<1:8000 deliveries) but carries 40% to 80% mortality with at least 50% permanent neurological damage in survivors.¹ Up to 50% of victims will die in the first hour of diagnosis. Approximately 70% occur during labor, 17% during cesarean section, and 11% during postpartum, but can also occur during pregnancy termination or amniocentesis.

The precise etiology of AFE is elusive, with no laboratory tests to confirm diagnosis.^1,2 Clinical pathophysiology stems from maternal infusions of fetal debris (amniotic fluid, meconium, fetal squamous cells, vernix) which causes an abnormal cellular response and anaphylactoid presentation. Systemic immune activation and thrombosis result from the exposure to the numerous immunologically active and prothrombotic substances found in amniotic fluid including platelet-activating factor, interleukins, complement factors, and tumor necrosis factor-alpha. Treatment is supportive.

RISK FACTORS

• Operative vaginal delivery

• Cesarean delivery

• Placenta previa

• Placental abruption

• Meconium

• Induction of labor

• Cervical lacerations

• Induction/augmentation of labor

• Difficult labor or very rapid labor

• Uterine rupture

• Eclampsia

• Polyhydramnios

• Multiple gestation

• Male fetus

DIAGNOSIS

Diagnosis^3,4

AFE is a clinical diagnosis. Clinical symptoms and signs of AFE often occur suddenly and profoundly, usually with altered mental status, followed by hypotension and fetal distress in nearly all severe cases (see Table 8-1). May progress rapidly to sudden cardiovascular collapse, cardiac arrest, severe respiratory difficulty and hypoxia, seizures, and disseminated intravascular coagulopathy (DIC). Dysrhythmias are common. Presenting signs and symptoms may occur in any order with variable persistence or severity. In many cases it is a diagnosis of exclusion, relying on autopsy for evidence, or ruling out other disorders (see Table 8-2). Clinical manifestations of AFE are easily remembered as a syndrome of 3Hs: hypoxia, hemodynamic instability, and hemorrhage.

PATHOPHYSIOLOGY AND RESPONSE

Clinical response in AFE is conceptualized better when described in phases.

• Phase 1: Entry of fetal material into the maternal ...