8: A Tale of Triple Trouble Hypoxia

Background: Methemoglobinemia is a dyshemoglobinemia in which hemoglobin is unable to bind oxygen, resulting in impaired oxygen delivery and tissue hypoxia. Acetanilide exposure is a known but uncommon cause. This case highlights a rare and complex presentation involving multiple simultaneous mechanisms of hypoxia, compounded by airway injury requiring extracorporeal life support. Case Presentation: A 37-year-old female with alleged exposure to acetanilide presented with severe respiratory distress and loss of consciousness. She was initially managed at a local hospital and referred for advanced care. Co-oximetry revealed severe methemoglobinemia at 43.9%. Chest radiography demonstrated right mainstem bronchial intubation with left lung collapse. The patient was treated with intravenous methylene blue at a dose of 2 mg per kg and endotracheal tube repositioning. Despite correction, hypoxia persisted with failure of left lung aeration. Bedside bronchoscopy revealed a transmural tracheal tear at the level of the carina extending into the left main bronchus. The patient experienced recurrent episodes of hypoxia with bradycardia and hypotension, necessitating vasopressor support. Due to unavailability of extracorporeal membrane oxygenation (ECMO) circuits, emergent peripheral venoarterial bypass via femoral cannulation was initiated. Following stabilization, surgical tracheal repair with a pericardial patch was successfully performed. The patient recovered and was discharged in stable condition on day 18. Conclusion: This case illustrates the coexistence of multiple hypoxic mechanisms, including methemoglobinemia, shunt physiology from lung collapse, ventilation perfusion mismatch, and airway disruption. Rapid diagnosis, methylene blue therapy, bronchoscopy, and timely extracorporeal support were critical to survival. In resource-limited settings, short-term peripheral venoarterial bypass may serve as an effective alternative to ECMO.