Malignant hyperthermia (MH) is a hypermetabolic response to certain inhaled anesthetic drugs with sudden, intense temperature elevation (hyperthermia) and muscle rigidity. Sustained contraction of skeletal muscles generates more heat than the body can dissipate. Other signs include hyperkalemia, tachycardia, tachypnea, acidosis, elevated carbon dioxide, increased oxygen consumption, and rhabdomyolysis. MH crisis constitutes a medical emergency. Incidence in the general population is estimated at 1:100 000 anesthetics administered.

Monitoring core temperature during surgical use of inhaled anesthetics can identify early MH.

MH crisis can be treated by immediately stopping the triggering anesthetic, administering dantrolene, treating hyperkalemia (hyperventilating), and lowering body temperature. Failure to treat MH crisis immediately leads to severe organ damage and death.

A predisposition to MH crisis is associated with an autosomal dominant pattern of inheritance caused by mutations in RYR1 and CACNA1S genes. Genetic skeletal muscle receptor abnormalities allow excessive calcium accumulation in response to anesthetic agents. Central core disease, King-Denborough syndrome, and central nuclear myopathy are also conditions that predispose patients to MH crisis.