Crush injury rhabdomyolysis — ABEM Board MCQ

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HardTraumaCrush injury rhabdomyolysisABEM Board

A 36-year-old man arrives as ESI 2 after inhaling smoke in an apartment fire. He has headache, confusion, lactate 9 mmol/L, soot around the mouth, and carboxyhemoglobin 18%. SpO2 reads 99%. Which of the following is the most likely diagnosis?

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Correct answer: C — Cyanide poisoning

This is cyanide poisoning from smoke inhalation. In enclosed-structure fires, combustion of nitrogen-containing/synthetic materials can release hydrogen cyanide. Cyanide inhibits mitochondrial cytochrome oxidase, preventing cellular oxygen utilization and causing rapid CNS toxicity with severe lactic acidosis despite apparently adequate oxygenation. The key exam clues are smoke exposure, soot around the mouth, headache/confusion, and lactate 9 mmol/L. A normal SpO2 does not exclude this diagnosis because pulse oximetry may appear normal in cyanide poisoning and is also unreliable with carboxyhemoglobin. The carboxyhemoglobin of 18% indicates concomitant carbon monoxide exposure, but among the listed options the syndrome with severe lactic acidosis after smoke inhalation is cyanide poisoning.

Reference: CDC/ATSDR. Medical Management Guidelines for Hydrogen Cyanide (HCN), Toxic Substance Portal, current online guidance. https://wwwn.cdc.gov/TSP/MMG/MMGDetails.aspx?mmgid=1141&toxid=249