Amniotic Fluid Embolism
The most likely diagnosis is amniotic fluid embolism (AFE), given the sudden onset of cyanosis, hypotension, and seizure immediately following precipitous delivery in a previously stable patient. This clinical triad of cardiovascular collapse, hypoxia, and altered mental status/seizure occurring in the immediate postpartum period is pathognomonic for AFE.
Clinical Reasoning
The presentation described—sudden cyanosis, profound hypotension (70/40 mm Hg), severe hypoxia (82% on high-flow oxygen), tachycardia, and tonic-clonic seizure immediately after precipitous delivery—represents the classic biphasic presentation of AFE:
- Phase 1 (cardiopulmonary collapse): The sudden cyanosis and hypotension with inadequate oxygenation despite 15 L/min oxygen indicates acute right heart failure and pulmonary hypertension from amniotic fluid entering maternal circulation
- Phase 2 (coagulopathy and hemorrhage): Often follows within hours, though the seizure and altered mental status can occur during the initial collapse phase
Why Not the Other Diagnoses
Eclampsia is unlikely because:
- Eclamptic seizures typically occur in patients with preceding hypertensive disorders of pregnancy, not sudden hypotension 1
- While postpartum eclampsia can occur (even up to 8 weeks postpartum in rare cases), it presents with hypertension (≥160/110 mmHg), not hypotension 2, 3, 4
- The profound cardiovascular collapse with cyanosis and oxygen saturation of 82% is not characteristic of eclampsia 5, 6
Pulmonary thromboembolism would present with:
- Sudden dyspnea and chest pain, but typically not with immediate seizure activity
- Less dramatic hypotension in most cases
- The timing immediately after precipitous delivery makes AFE more likely
Postpartum cardiomyopathy presents with:
- Gradual onset of heart failure symptoms over days to weeks
- Not sudden collapse immediately postpartum
- Would not explain the immediate seizure
Sepsis from chorioamnionitis would show:
- Fever and signs of infection during labor
- More gradual deterioration rather than sudden collapse
- Typically diagnosed before or during delivery, not suddenly after
Critical Management Considerations
The immediate postpartum timing after precipitous delivery combined with the triad of cardiovascular collapse, respiratory failure, and neurological compromise (seizure with unresponsiveness) makes AFE the diagnosis that must be assumed and treated emergently. AFE has mortality rates of 20-60% and requires immediate resuscitative measures including:
- Aggressive fluid resuscitation and vasopressor support
- Intubation and mechanical ventilation for severe hypoxia
- Preparation for massive transfusion protocol as coagulopathy typically follows
- Transfer to ICU with multidisciplinary team involvement
The key distinguishing feature is the sudden, catastrophic nature of the presentation immediately following delivery in a patient who was previously stable, which is the hallmark of AFE rather than the other differential diagnoses listed.