Pathophysiology
Clinical meaning
Cyanide (CN-) is a rapidly acting cellular asphyxiant that binds to cytochrome c oxidase (Complex IV) in the mitochondrial electron transport chain, halting aerobic metabolism. Despite adequate oxygen delivery, cells cannot utilize oxygen for ATP production, forcing reliance on anaerobic glycolysis. This produces profound lactic acidosis (type A -- tissue hypoxia despite adequate oxygen delivery) and cellular death within minutes of significant exposure. Sources include: smoke inhalation (combustion of synthetic materials releases hydrogen cyanide -- #1 cause in developed countries), industrial exposure (electroplating, mining, photography), ingestion of cyanogenic compounds (amygdalin in bitter almonds, apricot pits, cassava), and sodium nitroprusside metabolism (prolonged infusion produces cyanide). The classic finding is bright red/cherry-red venous blood (oxygen-rich because tissues cannot extract oxygen).