Apnea and unconsciousness after accidental subdural placement of an epidural catheter

Corresponding author: Bon-Nyeo Koo, M.D., Ph.D., Department of Anesthesiology and Pain Medicine, and Anesthesia and Pain Research Institute, Yonsei University College of Medicine, 50, Yonsei-ro, Seodaemun-gu, Seoul 120-752, Korea. Tel: 82-2-2228-2420, Fax: 82-2-312-7185, E-mail: [email protected] This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http:// creativecommons.org/licenses/by-nc/3.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. CC Subdural placement of an epidural catheter is a rare complication that may lead to life-threatening consequences. However, it is difficult to detect due to the variability of symptoms and signs and insufficient diagnostic guidelines. We recently experienced a case of subdural catheter placement that caused delayed emergence with respiratory depression and mental status change. A 56-year-old, 167cm, 68 kg male patient with stomach cancer was scheduled for subtotal gastrectomy with gastrojejunostomy. The patient was recently diagnosed with hypertension and otherwise healthy. Before induction of general anesthesia, a 20-gauge multiorifice epidural catheter was inserted for postoperative analgesia through an 18-gauge Tuohy needle at the T8-9 interspace using the paramedian approach in the sitting position. The epidural space was identified using the loss of resistance technique with saline and the catheter was advanced 6 cm upward. After aspiration for cerebrospinal fluid (CSF) and a bolus injection of a test dose for confirmation that the catheter was not within the subarachnoid or intravenous space, general anesthesia was induced. Before skin incision, a 10 ml epidural bolus of 1.5% lidocaine was administered and 0.15% ropivacaine with 3.6 ug/ml of fentanyl infusion was started at a rate of 4 ml/hr (Automed, Ace Medical Co., Goyang, Korea). A total dose of 15.3 ml of 0.15% ropivacaine and 55 μg of fentanyl had been epidurally administered throughout the uneventful 230 min operation and an additional epidural bolus of 10 ml of 0.225% ropivacaine mixed with 50 μg of fentanyl was given at the end of the operation. The patient was extubated after he could respond to verbal commands and return of neuromuscular function was confirmed. The patient showed normal vital signs. However, several minutes after tracheal extubation, the patient developed hypertension, tachycardia and respiratory depression while he became drowsy and gradually unresponsive to verbal commands and painful stimuli. The patient showed no improvement even after 30 minutes of assisted face mask ventilation with 100% oxygen, and continued to present with unconsciousness, irregular shallow respiration and constricted pupils. Assuming that this may have been caused by the subdural spread of fentanyl, the patient-controlled analgesic device was stopped and naloxone was given intravenously in increments of 200 μg at 2 min intervals. After 10 min, the patient regained consciousness and adequate spontaneous breathing, and 10 min later, he was fully awake and complained of abdominal pain. After transfer to the recovery room, naloxone was continuously infused intravenously and thoracolumbar radiography was performed to identify the location of the epidural catheter with 5 ml of radiocontrast dye (Omnipaque) injected through the catheter. X-ray in the lateral view showed a definite radiopaque feature in the posterior column in the subdural space (Fig. 1) and the catheter was removed. The patient was discharged on postoperative day 9 with full recovery. The incidence of subdural block is estimated to be 0.1% after intended epidural block [1] while some report a higher incidence of 7% [2]. Characteristic presentations are reported to be a negative aspiration test, limited or marked motor block,