ABSTRACT
Background: Various adjuvants are being used with local anesthetics for prolongation of intraoperative and post-operativeanalgesia. Among them, clonidine and dexmedetomidine are two α2-agonists which can be used as neuraxial adjuvants.Dexmedetomidine, a highly selective α2- adrenergic agonist, is a newer neuraxial adjuvant gaining popularity.Objectives: The objective of the study was to compare sensory and motor block characteristics, hemodynamic effects and sideeffects of low doses of clonidine or dexmedetomidine as an adjuvant to 12.5 mg hyperbaric bupivacaine in spinal anesthesiain lower-limb surgeries.Materials and Methods: A total of 90 patients of American Society of Anesthesiology I and II posted for lower-limbsurgeries were randomly allocated into three groups of 30 each. Group B received plain 12.5 mg of hyperbaric bupivacainediluted to 3 ml with normal saline. Group C received 30 mcg clonidine added to 12.5 mg hyperbaric bupivacaine anddiluted to 3 ml. Group D received 3 mcg dexmedetomidine added to 12.5 mg hyperbaric bupivacaine and diluted to 3 mlwith normal saline.Results: Patients in Group D and Group C had a significantly shorter onset time of sensory and motor block and significantlylonger duration of sensory and motor block compared to bupivacaine group. The mean time for sensory regression to S1 segmentwas 301.90 ± 31.96 min in Group D, 283.23 ± 13.59 min in Group C, and 181.70 ± 18.55 min in Group B (B vs. D and B vs. C,P < 0.001). There was a statistically significant difference in the two segment regression of sensory block in Group D (140.32± 17.6 min) when compared to Group C (124.5 ± 16.10 min) and Group B (92.13 ± 11.45 min). The regression of motor blockto Bromage 0 was 262 ± 24.40 min in Group D, 261 ± 24.19 min in Group C, and 164.40 ± 15.26 min in Group B (B vs. D andB vs. C, P < 0.0001). The onset and regression times were comparable between Groups D and C. Time for the first request ofrescue analgesia was nearly equal in Groups D and C and prolonged compared to Group B. Patients were hemodynamicallystable in all the groups.Conclusion: Dexmedetomidine and clonidine have a similar onset of sensory and motor block, prolonged duration of analgesia.Dexmedetomidine provides better analgesia than clonidine