Recrudescence of Opioid Effects After Intraoperative Remifentanil Infusion Complicated by Infiltration of the Intravenous Catheter

Abstract

To the Editor: We describe a case in which recrudescence of opioid effects occurred shortly after the emergence. A 77-yr-old woman (5[prime]6[prime], 65 kg) underwent microscopic direct laryngoscopy and laser excision of a supraglottic cyst. General anesthesia was induced with a remifentanil infusion of 0.5 [micro sign]g [center dot] kg-1 [center dot] min-1 and a propofol bolus of 1.0 mg/kg; succinylcholine 1.5 mg/kg was given to facilitate laryngoscopy and endotracheal intubation. Anesthesia was maintained with remifentanil, nitrous oxide 70% in oxygen, and isoflurane 0.2%. The remifentanil infusion rate was decreased to 0.25 [micro sign]g [center dot] kg-1 [center dot] min-1 1 min after intubation and to 0.125 [micro sign]g [center dot] kg (-1) [center dot] min-1 10 min thereafter. The succinylcholine infusion was titrated using a nerve stimulator. Thirty minutes into the procedure, the antecubital IV line had infiltrated. Approximately 162.5 [micro sign]g (0.125 [micro sign]g [center dot] kg-1 [center dot] min-1 x 65 kg x 20 min) of remifentanil had been infused. A second IV catheter was promptly inserted, and the succinylcholine and remifentanil infusions were restarted within 6 min. Fifteen minutes later, the succinylcholine infusion was stopped. Five minutes later, the surgery ended, and the nitrous oxide, isoflurane, and remifentanil were discontinued simultaneously. The IV tubing was flushed. Within 10 min, the patient was breathing regularly at a rate of 12 breaths/min; she seemed appropriate, responded to verbal commands, and demonstrated a 5-s head lift. She was tracheally extubated and transported to the recovery room. One minute after her arrival in the postanesthesia care unit, the patient's respiratory rate was 4 breaths/min, her heart rate was 40-45 bpm, and her SpO2 was 88%-92%. She did not respond to a vigorous painful stimulus (jaw thrust). We unsuccessfully attempted to ventilate the patient using a bag-valve-mask apparatus. After the administration of naloxone 40 [micro sign]g IV, her respiratory rate was 12 breaths/min, and her SpO2 improved. A repeat naloxone dose was given, and the patient responded appropriately to verbal stimuli. The patient's subsequent postoperative recovery was uneventful. Why did opioid effects recrudesce in this patient? We postulate that the interstitial remifentanil accumulation provided a sequestered repository from which remifentanil gradually diffused back into the circulation. We caution that remifentanil may have prolonged opioid effects when infused interstitially rather than directly into the circulation. Giovanni Cucchiaro, MD Richard A. Beers, MD Department of Anesthesiology; SUNY Health Science Center; Syracuse, NY 13210