| Summary: | Background: Alpha-2‑adrenergic agonists have synergistic action with local anesthetics and may prolong the duration of sensory and motor blockade and postoperative analgesia obtained with spinal anesthesia. The primary objective of this study was to compare the duration of analgesia, and the secondary objectives were to evaluate onset of sensory and motor blockade, perioperative sedation, hemodynamic changes, and adverse effects after intravenous (IV) infusion of clonidine and dexmedetomidine on spinal block characteristics as premedication to intrathecal 0.5% bupivacaine. Patients and Methods: This prospective, randomized, double blind study was conducted on a total of 100 patients belonging to the American Society of Anaesthesiologist class I and II undergoing lower limb and lower abdominal surgeries and were randomly allocated into two groups: Group CN (n = 50) received 1.5 µg/kg clonidine infusion and Group DM (n = 50) received 0.75 µg/kg dexmedetomidine infusion in 100 mL NS over 15 min before spinal anesthesia. Results: The duration of analgesia was statistically significantly prolonged in Group DM (251.70 ± 6.264 min) when compared with Group CN (213.02±10.374 min) (P < 0.001). The onset of sensory and motor blockade was faster in Group DM when compared with Group CN (P < 0.001). Recovery of sensory block was prolonged in Group DM when compared with Group CN (P < 0.001), but recovery of motor block was comparable in both the groups. The hemodynamic parameters were comparable in both the groups without any significant adverse effects. Conclusion: Premedication with IV dexmedetomidine infusion is better than that with IV clonidine infusion to provide intraoperative sedation and postoperative analgesia as premedication with hyperbaric bupivacaine 0.5% spinal anesthesia.
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