A 48-year-old man is brought to the emergency department 20 minutes after being rescued from a house fire. He reports headache, metallic taste, abdominal pain, and nausea. He appears confused and agitated. His pulse is 125/min, respirations are 33/min, and blood pressure is 100/65 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 98%. Physical examination shows a bright red color of the skin. His breath smells of bitter almonds. Hyperbaric oxygen therapy and appropriate pharmacotherapy are initiated. The expected beneficial effect of this drug is most likely due to which of the following mechanisms?

Question

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Eductional Objective: Cyanide impairs the mitochondrial enzyme cytochrome c oxidase, leading to histotoxic hypoxia. Clinically, this manifests as headache, altered mental status, tachycardia, flushed skin, and almond-scented breath. Nitrites oxidize hemoglobin into methemoglobin, which binds cyanide, thereby allowing oxidative phosphorylation to resume and symptoms to improve. Other important treatments include hydroxocobalamin (which binds cyanide to form the harmless compound cyanocobalamin) and sodium thiosulfate (converts cyanide to thiocyanide, which is then safely excreted).

A 48-Year-Old Man Is Brought to the Emergency Department 20