Magnesium Sulfate versus Clonidine As an Adjuvant to Ultrasound-Guided Supraclavicular Brachial Plexus Block in Upper Limb Surgery: A Double-Blind Randomized Controlled Trial

Objective: To compare the efficacy of clonidine and magnesium sulfate (MgSO4) when administered as an adjuvant to supraclavicular brachial plexus block in upper limb surgery. Materials and Methods: Sixty patients belonging to the American Society of Anesthesiologists classification (ASA) 1 and 2 undergoing upper limb surgical procedures were randomized to receive either 30 µg injection clonidine or 200 mg injection MgSO4 added to 18 ml of 0.5% levobupivacaine + 7 ml of 2% lignocaine with adrenaline. The primary objective of the study was to compare the duration of sensory (postoperative analgesia) and motor block between the two groups. The secondary objectives were to compare the onset time of motor and sensory block along with heart rate and mean arterial pressure between the two groups, which was recorded at regular intervals by the blinded anesthesiologist intraoperatively. Unpaired Student’s t-test and repeated-measures analysis of variance were used for the analysis of parameters between the two groups. Results: There was no statistically significant difference between clonidine and MgSO4 groups in terms of primary outcome, i.e., the duration of postoperative analgesia (12.10 ± 3.86 h vs. 10.93 ± 3.68 h, P = 0.236) or duration of motor block (10.67 ± 3.70 h vs. 9.50 ± 2.89 h, P = 0.180). The mean onset time for motor block was relatively faster in clonidine group compared to MgSO4 with a borderline significance (P = 0.049). No clinically significant difference was observed in the mean onset of sensory block or hemodynamics between the two groups. Conclusion: Both, clonidine and MgSO4, as an adjuvant to supraclavicular brachial plexus block were found to have a similar onset time and duration of analgesia and motor block.