Amniotic Fluid Embolism
Last updated: 09/27/2023
- Amniotic fluid embolism (AFE) is a rare but potentially life-threatening complication of pregnancy.
- AFE classically presents as acute respiratory distress, hypotension/hemodynamic instability, and coagulopathy.
- AFE occurs most often during labor and in the immediate postpartum period.
- Early recognition and aggressive resuscitation are crucial to improve maternal and fetal outcomes.
- Amniotic fluid embolism is a potentially catastrophic obstetric complication.
- The true incidence of AFE is unknown because of significant variability in the diagnostic criteria and reporting methodology used.1
- The mortality rate varies widely depending on the source, but may be as high as 60%.1
- There is no definitive test used to diagnose AFE, and the signs and symptoms are nonspecific.
• Emboli of fetal material alone are insufficient to trigger an AFE.
• The presence of fetal antigens leads to a cascade of inappropriately released inflammatory mediators (thromboxane, leukotrienes, prostaglandins, endothelins)1-3 (Figure 1).
- The previously used term “anaphylactoid syndrome of pregnancy” may then be inaccurate as the cascade likely causes mast cell degranulation, as opposed to the other way around.2
- Risk factors for AFE are listed in Table 1.
- AFE is a clinical diagnosis and there is no definitive test used to diagnose AFE.
- Commonly used clinical criteria have been established including:
- Acute hypotension, cardiac arrest/collapse
- Acute respiratory compromise
- Onset during labor, cesarean delivery, dilation and evacuation or within 30 minutes postpartum
- Absence of another clear cause or diagnosis
- Of note, AFE may also occur up to 48 hours postdelivery and after abdominal trauma, first trimester abortion, in the second trimester, and during an amnioinfusion.2
- The differential diagnosis is broad as many of the signs and symptoms are nonspecific (Table 2).
- Common signs and symptoms of AFE are listed in Table 3.
- There is a biphasic cardiovascular response during AFE.2
1. Within the first 30 minutes (Figure 2):
2. If the patient survives the first phase, left ventricular failure and pulmonary edema may result (Figure 3).
- With survival to the second phase, patients also concomitantly experience disseminated intravascular coagulation (DIC) and hemorrhage.
- However, AFE may present atypically with DIC and hemorrhage without preceding cardiovascular collapse.2
- The treatment of AFE is largely supportive.1
- Aggressive clinical management should focus on cardiovascular support, treatment of hypoxemia, and management of hemorrhage and coagulation abnormalities for the optimization of maternal and fetal well-being.
- Patients often present with cardiac arrest (Table 4).
- If there is evidence or high suspicion of acute RV failure, management includes:
- Vasopressors (i.e., norepinephrine)
- Inotropes (i.e., milrinone or dobutamine)
- Pulmonary vasodilators (i.e., inhaled nitric oxide or epoprostenol)
- Avoidance of excessive fluid administration
- If the patient remains hemodynamically unstable or requires prolonged CPR despite interventions, consider extracorporeal membrane oxygenation (ECMO).3
Disseminated Intravascular Coagulation
- Amniotic fluid contains tissue factor, which binds to factor VII and activates the coagulation cascade.3
- The coagulopathy is related to both consumption and hyperfibrinolysis.2,3
- Sultan P, Seligman K, Carvalho B. Amniotic fluid embolism: update and review. Curr Opin Anaesthesiol. 2016;29(3):288-96. PubMed
- Toledo P. Embolic disorders. In: Chestnut D, Wong CA, Tsen LC, Ngan Kee W, Beilin Y, Mhyre JM, Bateman B, eds. Chestnut’s Obstetric Anesthesia: Principles and Practice. 6th ed. Philadelphia: Elsevier; 2020: 943-48.
- Pacheco LD, Clark SL, Klassen M, et al. Amniotic fluid embolism: principles of early clinical management. Am J Obstet Gynecol. 2020;222(1):48-52. PubMed
- Stafford IA, Moaddab A, Dildy GA, et al. Amniotic fluid embolism syndrome: analysis of the Unites States International Registry. Am J Obstet Gynecol MFM. 2020;2(2):100083. PubMed
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