Delayed-onset malignant hyperthermia in the postanesthetic care unit: a case report.

Malignant hyperthermia (MH) is a potentially fatal hypermetabolic syndrome that occurs when susceptible individuals are exposed to triggering agents. Variability in the order and time of occurrence of symptoms often makes clinical diagnosis difficult. A late diagnosis or misdiagnosis of delayed-onset MH may lead to fatal complications. We herein report a case of delayed-onset MH in the postoperative recovery room. A 77-year-old man awoke from anesthesia and was transferred to the recovery room. Ten minutes after his arrival, his mental status became stuporous and he developed masseter muscle rigidity, hyperventilation, and a body temperature of 39.8°C. The patient was suspected to have MH, and 60 mg of dantrolene sodium (1 mg/kg) was administered via intravenous drip with symptomatic treatment. Within 10 minutes of dantrolene administration, the patient's clinical signs subsided. This case report demonstrates that rapid diagnosis and treatment are crucial to ensure a good prognosis for patients with MH. A high level of suspicion based on clinical symptoms and early administration of therapeutic drugs such as dantrolene will also improve the clinical course. Therefore, suspicion and prompt diagnosis are absolutely essential. This case report emphasizes the importance of continuous education in the diagnosis and treatment of MH.