A prospective, double-blind dose-ranging study of intrathecal nalbuphine in the lower abdominal and lower limb surgeries

Abstract

Background: Nalbuphine is a synthetic opioid with mixed agonist-antagonist action, used as an adjuvant with intrathecal bupivacaine to prolong postoperative analgesia. However, only a few studies so far have quantified the optimal intrathecal nalbuphine dose. Our aim was to compare the relative effectiveness of three doses of intrathecal nalbuphine to determine the optimum dose which prolonged analgesia with minimal side effects. Settings and Design: This was a prospective, randomized, double-blind study. Subjects and Methods: Eighty American Society of Anesthesiologists I and II patients undergoing elective lower abdominal and lower limb surgeries under subarachnoid block were randomly allocated to four groups (A, B, C, and D of twenty patients each) to receive 0.5 ml normal saline or 0.8, 1.2, and 1.6 mg nalbuphine added to 0.5% hyperbaric bupivacaine 15 mg. The onset of sensory and motor blockade, two-segment regression time of sensory blockade, duration of motor blockade, duration of analgesia, visual analog scale pain score, and side effects were compared between these groups. Results: Two-segment regression time of sensory blockade and duration of effective analgesia were prolonged in both Group C (1.2 mg nalbuphine) and Group D (1.6 mg nalbuphine) compared to Groups A and B (P < 0.05), but the incidence of side effects was significantly higher in Group D (P < 0.05). Conclusion: Nalbuphine 1.2 mg is the optimum intrathecal dose which prolongs postoperative analgesia without increased side effects.