Comparative Evaluation of Dexmedetomidine versus Fentanyl Added to Hyperbaric Levobupivacaine for Subarachnoid Block: Effects on Sensory-Motor Blockade and Analgesic Duration

Introduction: Adjuvants to local anesthetics enhance the quality and duration of spinal anesthesia while reducing postoperative analgesic requirements. Opioids like fentanyl are effective but associated with significant side effects, whereas dexmedetomidine, an α2-adrenergic agonist, has shown promise as a non-opioid alternative. Objective: To compare the effects of intrathecal dexmedetomidine and fentanyl, when added to levobupivacaine, on sensory and motor block characteristics, duration of analgesia, and complications in patients undergoing elective total abdominal hysterectomy. Methods: In this prospective, double-blind, randomized controlled trial, 60 ASA I–II female patients aged 18–65 years were allocated into two groups (n = 30 each). Group D received 15 mg 0.5% hyperbaric levobupivacaine with 5 μg dexmedetomidine, and Group F received 15 mg 0.5% hyperbaric levobupivacaine with 25 μg fentanyl intrathecally. Block onset, duration of sensory and motor blockade, time to first rescue analgesia, hemodynamic changes, and side effects were recorded. Results: Demographic variables were comparable between groups. The onset of sensory and motor block was significantly faster with fentanyl, while dexmedetomidine prolonged the duration of sensory block (458.83 vs 358.07 min, p < 0.001), motor block (287.33 vs 217.33 min, p < 0.001), and time to rescue analgesia (95.5 vs 55.5 min, p < 0.001). Hypotension was the most common complication in both groups, without significant difference between two groups. Pruritus was observed only in the fentanyl group, while bradycardia was rare and not significant in the dexmedetomidine group. Conclusion: Intrathecal dexmedetomidine, as an adjuvant to levobupivacaine, provides prolonged sensory and motor block and superior postoperative analgesia compared to fentanyl, with fewer side effects. It may be considered a preferable adjuvant for spinal anesthesia in total abdominal hysterectomy.