Intrathecal nalbuphine versus intrathecal fentanyl as adjuvant to 0.5% hyperbaric bupivacaine for orthopedic surgery of lower limbs under subarachnoid block: A comparative evaluation

Background: Subarachnoid block (SAB) possesses many benefits with a drawback of short duration of anesthetic action. Intrathecal opioids have been used to enhance the clinical efficiency and duration of action of local anesthetic drugs. The present study was aimed to compare the clinical efficiency of intrathecal fentanyl with nalbuphine as adjuvant to 0.5% hyperbaric bupivacaine for orthopedic surgery of lower limbs. Patients and Methods: Sixty-eight adult patients of American Society of Anesthesiologist physical status I and II of both gender aged 25-65 years were randomized into two groups of 34 each to receive either fentanyl 25 μg (Group I) or nalbuphine 2 mg (Group II) with 3.5 mL 0.5% hyperbaric bupivacaine, making intrathecal drug volume to 4 mL in each group. Sensory and motor block characteristics and time to first rescue analgesic (intravenous tramadol 100 mg) were recorded as the primary end points. Drug-related side effects of pruritus, nausea/vomiting, and respiratory depression were recorded as the secondary outcomes. Results: Both groups were comparable regarding the onset and cephalic extension of block. The time to two dermatome regressions and time for complete motor recovery were significantly prolonged in patients of Group II with statistical significant difference (P < 0.05). Duration of analgesia was also extended in patients of Group II (378.0 ± 35.72 min) as compared to Group I (234.0 ± 24.10 min) with highly significant difference (P < 0.001). No drug-related side effects were observed in either group. Conclusion: Intrathecal nalbuphine 2 mg as adjuvant to 0.5% bupivacaine was clinically more efficient than fentanyl for enhancing the postoperative analgesia.