Malignant hyperthermia is a hypermetabolic disorder of skeletal muscle characterized by catabolism and contracture, usually secondary to inhalant anesthetic agents and stress. It is seen most frequently in heavily muscled dogs. Abnormal calcium regulation, glycogenolysis, and contractile protein activity result in production of heat, CO2, and lactic acid.
Clinical signs include tachycardia, tachypnea, fever, muscle rigidity, and cardiopulmonary failure. Signs develop 5–30 minutes after exposure to the anesthetic agent. Treatment consists of immediate cessation of anesthesia and hyperventilation with oxygen. IV fluid therapy, corticosteroids, and ice packs are also used. Dantrolene, a muscle relaxant, may be given at 2–5 mg/kg, IV. Prognosis is poor in severe cases. Urinary output, serum potassium levels, and cardiac function should be monitored.