Malignant hyperthermia (MH) is a life-threatening pharmacogenetic disorder of skeletal muscle that presents as a hypermetabolic crisis during or after general anesthesia. The mortality rate has decreased dramatically with early recognition and dantrolene availability, but delayed diagnosis remains the primary risk factor for poor outcomes. Every anesthesia provider must be prepared to recognize and treat MH without delay.
Hypermetabolic crisis triggered by volatile agents and succinylcholine in genetically susceptible patients
Earliest sign is unexplained rise in end-tidal CO2; tachycardia, rigidity, and hyperthermia follow
Dantrolene 2.5 mg/kg IV initial dose, repeated every 5 minutes up to 10 mg/kg or until symptoms resolve
Incidence approximately 1:5,000–1:50,000 general anesthetics depending on population
RYR1 gene mutation is the most common genetic basis; caffeine-halothane contracture test remains the gold standard diagnostic
Do not wait for temperature elevation to suspect MH. Unexplained ETCO2 rise, masseter muscle rigidity after succinylcholine, and unexplained tachycardia should trigger immediate workup. Call the MHAUS hotline at 1-800-644-9737 during any suspected episode.
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