Amniotic fluid embolism

Pathophysiology - The Perfect Storm

• Trigger: Breach of the maternal-fetal barrier, allowing amniotic fluid, fetal cells, and debris to enter maternal circulation.
• Mechanism: Anaphylactoid-like reaction, not a true embolism. Fetal antigens trigger massive maternal inflammatory response.

⭐ Key Insight: AFE is primarily an immunological reaction, not a mechanical obstruction. The resulting DIC is often the most challenging aspect to manage, characterized by massive hemorrhage with simultaneous thrombosis.

Clinical Presentation - Sudden, Swift, Scary

• Sudden Onset: Abrupt cardiorespiratory collapse during labor, delivery, or within 30 minutes postpartum.
• Phase 1: Cardiopulmonary Collapse
  • Rapid-onset dyspnea, cyanosis, and severe hypotension.
  • Pulmonary edema & ARDS picture.
  • Neurological signs: Seizures, confusion, coma.
• Phase 2: Coagulopathy & Hemorrhage
  • Develops in survivors of the initial phase.
  • Massive hemorrhage with uterine atony.
  • Signs of Disseminated Intravascular Coagulation (DIC): bleeding from venipuncture sites, petechiae.

⭐ The most common initial signs are cardiac arrest, followed by hypotension and fetal distress.

Diagnosis & Differentials - Rule-Out Rodeo

• Clinical Diagnosis: AFE is a diagnosis of exclusion; no single test is confirmatory. Diagnosis is based on the classic triad of sudden hypoxia, hypotension, and coagulopathy.
• Initial Workup: Focuses on stabilization and ruling out other causes.
  • Labs: ABG, CBC, coagulation panel (↑PT/PTT, ↓fibrinogen, ↑D-dimer).
  • Imaging: Chest X-ray (may show pulmonary edema), ECG (to rule out MI), Echo (to assess for right heart failure).

⭐ While historically taught, finding fetal squamous cells or lanugo in the maternal pulmonary circulation at autopsy is neither sensitive nor specific for AFE.

Management - All Hands on Deck

• Immediate Multidisciplinary Response: Activate code team (ICU, Anesthesia, OB, Hematology).
• Cardiopulmonary Support (A-B-C):
  • Airway/Breathing: Intubation and 100% O₂ to maintain SpO₂ >90%.
  • Circulation: Large-bore IVs, vasopressors (norepinephrine), and inotropes (dobutamine) for shock.
• Hemorrhage & Coagulopathy Control:
  • Activate Massive Transfusion Protocol (1:1:1 ratio of pRBCs:FFP:Platelets).
  • Administer cryoprecipitate to maintain fibrinogen >150-200 mg/dL.
• Delivery:
  • Crucial for maternal stabilization; proceed with immediate C-section.

⭐ Initiate perimortem C-section within 4-5 minutes of maternal cardiac arrest to relieve aortocaval compression, improving resuscitation success for both mother and baby.

High‑Yield Points - ⚡ Biggest Takeaways

• A rare, catastrophic complication causing sudden cardiorespiratory collapse during labor or immediately postpartum.
• Characterized by the classic triad of acute hypoxia, severe hypotension, and disseminated intravascular coagulopathy (DIC).
• Pathophysiology involves an anaphylactoid-like reaction to fetal antigens entering maternal circulation.
• Presents with abrupt respiratory distress, seizures, and massive hemorrhage.
• Diagnosis is clinical and remains a diagnosis of exclusion.
• Management is purely supportive: intubation, vasopressors, and massive transfusion protocol.