Effect of Different Doses of Intrathecal Nalbuphine as Adjuvant to Hyperbaric Bupivacaine on Characteristics of Subarachnoid Block in Pelvic and Lower Limb Orthopaedic Surgeries: A Randomised Clinical Study

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Introduction: Hyperbaric bupivacaine 0.5% is most commonly used amide local anaesthetic drug in spinal anaesthesia. Various additives have been used as an adjuvant to hyperbaric bupivacaine 0.5% to modify its anaesthetic properties. Nalbuphine, a mix opioid with high efficacy kappa receptors agonism has also been used as an adjuvant to hyperbaric bupivacaine 0.5% at different doses. Aim: To compare and discover the effective dose of nalbuphine as adjuvant in subarachnoid block with hyperbaric bupivacaine in pelvic and lower limb orthopaedic surgeries in terms of onset and duration of sensory and motor block along with postoperative analgesia duration. Materials and Methods: This randomised clinical study was conducted in the Department of Anaesthesia, Shrimati Bhikhiben Kanjibhai Shah Medical Institute and Research Centre (SBKS MIRC), Piparia, Vadodara, Gujarat, India over a period of 18 months from February 2023 to August 2024 on 80 patients belonging to 20-60 years of age, American Soceity of Anaesthesiology (ASA) Grade I or II, of either gender undergoing elective pelvic and orthopaedic surgeries. Patients were randomly divided into two groups having 40 patients each. Group A received hyperbaric bupivacaine 12.5 mg+0.4 mg nalbuphine (total 3 mL) and Group B received hyperbaric bupivacaine 12.5 mg + 0.8 mg nalbuphine (total 3 mL). Sensory and motor block characteristics like their onset time, time to achieve highest sensory level, time to achieve bromage 3, time of two segment regression, duration of sensory and motor block, duration of postoperative analgesia and time for requirement of first rescue analgesia dose were observed and assessed. Haemodynamic parameters along with intraoperative and postoperative sideeffects were also observed. Results: Both the study groups had similar demographics and haemodynamic parameters. Time of two segment regression of sensory block was significantly longer in Group B (135.25±11.49 min) than A (120.95±16.98 min) with statistically significant prolonged duration of sensory block in Group B (228.25±21.91 min) than A (206.75±15.21 min) (p<0.0001). Postoperative analgesia was also prolonged in Group B (294.75±19.15 min) than A (226.19±14.78 min) without significant increase the incidence of side-effects (p≥0.05). Conclusion: Study concluded that 0.8 mg nalbuphine as an adjuvant to 0.5% hyperbaric bupivacaine in subarachnoid block is more effective dose as it provides prolonged duration of sensory block and postoperative analgesia with good haemodynamic stability and minimal side-effects.