Effect of Midazolam and Dexmedetomidine Sedation on the Onset and Duration of Supraclavicular Brachial Plexus Block: A Randomised Comparative Study

Objective: Prolonging the duration of sensory blockade with bupivacaine following supraclavicular brachial plexus block is desirable for improved postoperative pain management. This study was conducted to assess the effect of intravenous dexmedetomidine on the onset and duration of supraclavicular brachial plexus block using bupivacaine. Methods: Sixty ASA I and II adult patients undergoing upper limb surgery under supraclavicular brachial plexus block were included in this prospective, randomised, double-blind study. They were randomly divided into two groups. The first group was administered midazolam at an initial dose of 0.04 mg kg(-1) in 10 mL of normal saline infused over 10 min, which was followed by maintenance infusion of 0.04 mg kg(-1) h(-1). The second group was administered 0.5 mu g kg(-1) of dexmedetomidine in 10 mL of normal saline infused over 10 min, which was followed by maintenance infusion of 0.5 mu g kg(-1) h(-1). Twenty-five millilitres of bupivacaine (0.5%) was injected for supraclavicular brachial plexus block. Results: The onset of sensory block (16.6 +/- 1.9 vs. 19.8 +/- 1.7 min) and motor block (19.5 +/- 2.7 vs. 23.6 +/- 1.4 min) was significantly faster in the dexmedetomidine group than in the midazolam group (p<0.001). The duration of sensory block (738 +/- 66.3 vs. 307.7 +/- 46.7 min) and motor block (645.0 +/- 106.0 vs. 268.8 +/- 32.7 min) was significantly higher in the dexmedetomidine group than in the midazolam group (p<0.001). Conclusion: Intravenous dexmedetomidine in combination with 25 mL of bupivacaine (0.5%) accelerated the onset of sensory and motor block and prolonged the duration of sensory and motor block when used for brachial plexus block, without resulting in any adverse events.