Drug overdose due to malfunction of a patient-controlled analgesia machine -A case report-
A 71-year-old woman (height, 154 cm; weight, 57 kg) underwent vaginal total hysterectomy and anterior-posterior vaginal wall repair for uterine prolapse. Her medical history was unremarkable. Findings of routine preoperative laboratory tests, chest radiography, and electrocardiography were within normal limits.\nThe patient received general anesthesia for the procedure. The duration of anesthesia was 150 minutes. Estimated blood loss was 200 ml, and the infused fluid was Hartmann solution (1,500 ml). There were no adverse events or complications during anesthesia and surgery. The patient was transferred to the post-anesthesia care unit. An intravenous PCA machine (AutoMed3400®Ace Medical, Seoul, Korea) was connected, and the nurse pushed the button once. The PCA solution contained 1,000 µg fentanyl (Fentanyl citrate® HanLim Pharm, Korea), 120 mg tarasyn (Ketorolac Tromethamine® Roche Pharm, Korea), and 32 mg ondant (Ondansetron® Hanmi Pharm, Korea) mixed with 100 ml normal saline in a total volume of 140 ml. The bolus dose was 2 ml. The PCA was set at a basal rate of 2 ml/hr, with a lock-out time of 12 minutes. The patient complained of being cold, so an air warmer was applied. No difficulties were observed. The patient's mental functions were intact, and her vital signs were stable. Blood pressure (BP) was 120/75 mmHg; heart rate (HR), 65 bpm; and oxygen saturation (SpO2), 99%.\nAfter 30 minutes, the nurse was alerted by an alarm from the pulse oximeter indicating an SpO2 of 80%. The patient was unresponsive and had a very low respiratory rate. Her BP had decreased to 65/48 mmHg. Immediate resuscitative measures were performed. Ephedrine (30 mg) was administered intravenously. The patient was intubated and manually resuscitated for 10 minutes. The PCA machine indicator showed a total infused volume of 31 ml, indicating that the patient had received 221 µg fentanyl and 26 mg tarasyn. The patient was immediately disconnected from the PCA machine. Fortunately, the patient showed rapid improvement in consciousness and ventilation. In 20 minutes, she was fully alert, and her vital signs had stabilized. Her BP was 130/80 mmHg; HR, 80 bpm; and SpO2, 100%. Extubation was performed, and close observation was maintained. The patient was sent to the ward and discharged from the hospital 1 week later, without further complications.