Antagonism of Postoperative Opioid-Induced Respiratory Depression

Abstract

The authors compared naloxone and nalbuphine as antagonists of opioid-induced respiratory depression to determine the relative efficacies and safety of the two agents. In a double-blind, randomized fashion, 90 anesthetized patients received a mean dose of 25 μg/kg fentanyl during surgery. Inadequate spontaneous respirations at the end of anesthesia were treated with either naloxone 0.08 mg or nalbuphine 2.5 mg IV every 2 min while heart rate (HR), systolic and diastolic blood pressures (SBP, DBP), respiratory rate (RR), and tidal volume (TV) were measured at 2-min intervals. Arterial blood samples for analysis of Paco2, Pao2, and pH were drawn when spontaneous ventilation resumed, and 30 and 60 min later. Narcotic antagonism and respiration were deemed adequate when TV was ≥ 4 ml/kg and RR ≥ 8 breaths/min. Heart rate, SBP, DBP, TV and RR were recorded, as were the occurrence of renarcotization (RR < 8) and analgesic requirements every 5 min during the recovery room stay. Sixty of 90 patients required narcotic antagonism at the end of surgery. No patient required more than three doses (0.24 mg) of naloxone or four doses (10 mg) of nalbuphine. Both antagonists produced similar and moderate increases in SBP and HR while restoring adequate spontaneous ventilation. There were no significant differences in TV, RR, or arterial blood gases (ABGS) between the two groups after narcotic reversal. Five patients in whom respiratory depression was antagonized with naloxone and two receiving nalbuphine became renarcotized 30--90 min after entering the recovery room (not statistcally different), but patients given naloxone required analgesics for pain significantly more often than those reversed with nalbuphine (12 vs 5). With the exception of providing better immediate postoperative analgesia, small doses of nalbuphine and naloxone are equally effective and safe antagonists of opioid respiratory depression after operation.