A 28-year old woman in DM (Ed note: Define DM) and chronic renal failure underwent an uneventful open reduction and internal fixation for an ankle fracture under spinal anesthesia. PCA with fentanyl and tramadol was started in the operating room with a background infusion of 2 ml/hr (10 µg/h of fentanyl and 6 mg/h of tramadol), a bolus dose of 2 ml and a lockout interval of fifteen minutes. Approximately eight hours after initiating PCA the patient was found unresponsive in the ward with respiratory failure. Resuscitation was started with endotracheal intubation and cardiac massage with an injection of epinephrine and atropine. The patient made a full and immediate recovery two hours later.