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Amniotic Fluid Embolism — FRCA Final MCQ

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HardObstetric AnaesthesiaAmniotic Fluid EmbolismFRCA Final

A 35-year-old woman at 30 weeks' gestation develops sudden agitation, dyspnoea, cyanosis and profound hypotension immediately after artificial rupture of the membranes. Her SpO2 is 85% and blood pressure is 75/40 mmHg; the fetal heart rate falls to 70 beats min−1. Transthoracic echocardiography shows acute right ventricular dilatation with an underfilled left ventricle. Within minutes, there is persistent bleeding from venepuncture sites, with a fibrinogen concentration of 0.8 g L−1. There is no significant vaginal bleeding, and the uterus is soft and non-tender. What is the most likely diagnosis?

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Correct answer: E — Amniotic fluid embolism

The correct answer is E, amniotic fluid embolism. The characteristic combination is abrupt peripartum hypoxaemia, cardiovascular collapse, fetal compromise and rapidly developing consumptive coagulopathy. Acute pulmonary vasoconstriction and right ventricular failure can produce the echocardiographic appearance of massive pulmonary embolism, but early severe hypofibrinogenaemia and diffuse bleeding strongly favour AFE. Massive thrombotic pulmonary embolism does not usually produce immediate profound DIC. Placental abruption can cause fetal bradycardia and consumptive coagulopathy, but would usually be accompanied by vaginal bleeding, uterine pain or a tense, tender uterus and does not primarily cause abrupt hypoxaemia. Air embolism may cause sudden right-sided obstruction and hypoxaemia but not rapid consumptive coagulopathy. Peripartum cardiomyopathy typically presents with left ventricular systolic dysfunction rather than this acute syndrome. AFE is a clinical diagnosis after considering competing causes.

Reference: Metodiev Y, Ramasamy P, Tuffnell D. Amniotic fluid embolism. BJA Education. 2018;18(8):234–238. https://pubmed.ncbi.nlm.nih.gov/33456838/