The high calcium concentration affects the muscles by stimulating contraction and a hypermetabolic state which presents as rigidity and fever. Malignant hyperthermia can be suspected if less than normal muscle relaxation occurs during induction of anesthesia or when muscle fasciculations become apparent when succinylcholine is given. High fever is the result of muscle contraction, tachycardia or cardiac arrhythmia, high blood pressure or vasoconstriction may also occur. Early laboratory tests show respiratory and metabolic acidosis and hypermagnesemia as well as elevation in blood lactate and pyruvate. Later there may be massive skeletal muscle swelling, pulmonary edema, disseminated intravascular coagulation and acute renal failure.
Malignant hyperthermia is a medical emergency.
Treatment includes interruption of surgery and cooling the patient with ice. Oxygen should be given and sodium bicarbonate can be used to combat metabolic acidosis. Intravenous treatment with dantrolene sodium can halt the process by inhibiting the release of calcium. Malignant hyperthermia can be prevented by monitoring the temperature of all patients under general anesthesia and by taking a thorough history before surgery to detect familial tendency to have the disease. Examining patients preoperatively is not necessarily helpful because many people are normal between attacks.