Malignant hyperthermia. Current concepts.

At least three myopathies have been associated with malignant hyperthemia (MH). The clinical manifestations of MH are variable and depend on the nature of the underlying myopathy and the anesthetic agents administered. Unless muscle relaxants are used, fever and muscle rigidity may be delayed at onset. Tachycardia and tachypnea are often the earliest manifestations and can occur immediately or several hours into a surgical procedure. Life-threatening cardiac arrhythmias may result from hyperkalemia and acidosis. A hyperthermic reaction developed in an 8-year-old boy with a family history of Duchenne's muscular dystrophy one hour after induction of anesthesia. Temperature elevation and muscle rigidity were minor components of the condition. Determination of arterial blood gas concentrations and the serum potassium level established the diagnosis and enabled the start of lifesaving therapy.