Comparison of dexmedetomidine and clonidine (alpha 2 agonist drugs) as an adjuvant to local anaesthesia in supraclavicular brachial plexus block: A randomised double-blind prospective study

Background and Objectives: Alpha-2 agonists are mixed with local anaesthetic agents to extend the duration of spinal, extradural and peripheral nerve blocks. We compared clonidine and dexmedetomidine as an adjuvant to local anaesthetic agent in supraclavicular brachial plexus block with respect to onset and duration of sensory and motor block and duration of analgesia. Methods: Sixty ASA I and II patients scheduled for elective upper limb surgeries under supraclavicular brachial plexus block were divided into two equal groups in a randomized, double-blinded fashion. Group C received clonidine 1 mu g/kg and Group D received dexmedetomidine 1 mu g/kg added to bupivacaine 0.25% (35 cc). Onset and recovery time of sensory and motor block, duration of analgesia and quality of block were studied in both the groups. Results: Duration of sensory block and motor block was 227.00 +/- 48.36 and 292.67 +/- 59.13 min, respectively, in group C, while it was 413.97 +/- 87.13 and 472.24 +/- 90.06 min, respectively, in group D. There was no statistically significant difference in onset of sensory and motor block between the two groups. The duration of analgesia (time to requirement of rescue analgesia) in group D was 456 +/- 97 min, while in group C, it was 289 +/- 62 min. Statistically, this difference was significant (P=0.001). The number of patients achieving grade IV quality (excellent) of block was higher in group D (80%) as compared with group C (40%) (P<0.05). Conclusion: Dexmedetomidine when added to local anaesthetic in supraclavicular brachial plexus block enhanced the duration of sensory and motor block and also the duration of analgesia. The time for rescue analgesia was prolonged in patients receiving dexmedetomidine. It also enhanced the quality of block as compared with clonidine.