Respiratory arrest following diazepam administration during spinal anesthesia in a patient with myotonic dystrophy

A 43 year old female with previously undiagnosed myotonic dystrophy received abdominal hysterectomy under spinal anesthesia. Respiratory arrest occurred when diazepam 5 mg was slowly administered intravenously during operation. Mask ventilation was continued during operation with nitrous oxide and pentazocine 30 mg i.v. After the operation ventilatory failure continued. Arterial blood gas analysis revealed pH; 7.21, Pao2; 57 mmHg, Paco2; 82 mmHg in spite of oxygen therapy by a face mask. For 5 days after the operation, oxygen therapy was necessary. The patient was diagnosed as myotonic dystrophy by further examination after the operation. In a patient with myotonic dystrophy, we should be very careful in administering a drug which may cause respiratory depression to prevent respiratory complication.