[Prolonged respiratory depression following general anesthesia in a patient with dystrophia myotonica]

A case of general anesthesia for a 52 year old female with previously undiagnosed dystrophia myotonica was reported. The patient was diagnosed as flaccid paralysis of the bilateral lower extremities but myotonic symptoms were not found preoperatively. The patient underwent duodenal resection to have a benign tumor removed. Anesthesia was induced with thiamylal 250 mg and pancuronium bromide 4 mg intravenously to facilitate tracheal intubation. Anesthesia was maintained with enflurane (0.6-1.0%) in nitrous oxide (50%) and oxygen (50%). The course of anesthesia was uneventful except for a transient hypotension of 80 mmHg systolic for about 10 minutes. The patient did not recover smoothly from anesthesia and prolonged apnea was observed. 90 minutes after the end of surgical procedure, spontaneous ventilation appeared. Then the tidal volume increased gradually but it still remained around 100-150 ml even 3 hours after the end of the operation. She was on ventilator and observed carefully. The endotracheal tube was removed four days after the operation. The patient was examined again by a neurologist and a final diagnosis of dystrophia myotonica was made. Prolonged recovery from anesthesia and postoperative respiratory depression observed in this patient was due to preoperatively undiagnosed dystrophia myotonica. A careful preoperative examination should be made to minimize possible complication related to anesthesia in the disease.