A Comparative Study of Intrathecal Dexmedetomidine and Fentanyl as Adjuvants to 0.5% Hyperbaric Bupivacaine in Spinal Anaesthesia for Infraumbilical surgeries

Abstract

Introduction: Intrathecal adjuvants are commonly used with hyperbaric bupivacaine to prolong spinal anaesthesia and improve postoperative analgesia. Dexmedetomidine, a selective α2-adrenergic agonist, has shown promising results as an alternative to opioids such as fentanyl in subarachnoid block. The present study aimed to compare the efficacy and safety of intrathecal dexmedetomidine and fentanyl as adjuvants to 0.5% hyperbaric bupivacaine in patients undergoing infraumbilical surgeries. Materials and Methods: This prospective, randomized, double-blind controlled study was conducted in the Department of Anaesthesiology at Adichunchanagiri Institute of Medical Sciences, Adichunchanagiri University, between January 2025 and December 2025. Sixty ASA I and II patients aged 18–60 years undergoing elective infraumbilical surgeries under spinal anaesthesia were randomly allocated into two groups of 30 each. Group D received 12.5 mg of 0.5% hyperbaric bupivacaine with 2.5 µg dexmedetomidine, while Group F received 12.5 mg of 0.5% hyperbaric bupivacaine with 25 µg fentanyl. Sensory and motor block characteristics, postoperative analgesia, hemodynamic parameters, and adverse effects were assessed. Results: Group D demonstrated significantly faster onset of sensory block at T10 (2.84 ± 0.68 min vs 3.62 ± 0.81 min; p<0.001) and prolonged duration of sensory block (521.8 ± 61.7 min vs 336.4 ± 48.2 min; p<0.001) compared to Group F. Time to first rescue analgesia was significantly longer in Group D (468.2 ± 58.4 min vs 284.6 ± 39.5 min; p<0.001), with lower NRS pain scores at 6 hours. Mean heart rate and MAP were lower in Group D during the intraoperative period but remained clinically manageable. Incidence of adverse effects was comparable between groups, with pruritus observed only in the fentanyl group. Conclusion: Intrathecal dexmedetomidine as an adjuvant to hyperbaric bupivacaine provided superior sensory and motor blockade, prolonged postoperative analgesia, and reduced analgesic requirement compared to fentanyl with acceptable hemodynamic stability and minimal adverse effects.