Malignant hyperthermia is a life-threatening condition resulting from a genetic sensitivity of skeletal muscles to volatile anaesthetics and depolarizing neuromuscular blocking drugs that occurs during or after anaesthesia.

The incidence has been reported to be between 1:4,500 to 1:60,000 procedures involving general anaesthesia. This disorder occurs worldwide and affects all racial groups. Most cases however occur in children and young adults. There is a strong family association for this condition, which is inherited in an autosomal dominant pattern. Halothane, an obsolete volatile anaesthetic, has been linked to a large proportion of cases.

The phenomenon presents with muscular rigidity, followed by a hypermetabolic state showing increased oxygen consumption, increased carbon dioxide production, and increased temperature (hyperthermia), proceeding to rhabdomyolysis with rapid rising of myoglobin, creatine kinase (CK/CPK) and potassium.

After the widespread introduction of treatment with dantrolene the mortality of malignant hyperthermia fell from 80% in the 1960s to less than 10%.