Comparison of a Single- or Double-Injection Technique for Ultrasound-Guided Supraclavicular Block A Prospective, Randomized, Blinded Controlled Study

Background: Despite good success rates reported with ultrasound-guided supraclavicular block using 1 or multiple injections, no consensus exists on the best technique to use. We designed this study to test the hypothesis that a double-injection technique would hasten the onset of sensory block. Methods: Adult patients undergoing hand, wrist, or elbow surgery were enrolled in this prospective double-blind randomized study. Blocks were performed under ultrasound guidance. In group S (single injection), 30 mL of mepivacaine 1.5% was injected at the junction of the subclavian artery and the first rib. In group D (double injection), 15 mL of the same solution was injected at the site described above, then 15 mL was injected in the most superficial portion of the lateral aspect of the cluster formed by the brachial plexus trunks and divisions. The primary end point was the rate of complete sensory block at 15 mins. Secondary end points were the rates of sensory, motor, and surgical blocks and procedure time. Results: Fifty-one patients were randomized to each group. The rate of complete sensory block was similar at 15 mins (group S: 49% [95% confidence interval, 36%-62%], group D: 53% [95% confidence interval, 40%-66%]; P = 0.80) and at each time interval. The rates of complete motor block and surgical block success were similar between groups. The procedure time was shorter in group S (179 +/- 104 vs 275 +/- 137 secs; P < 0.01). Conclusions: The double-injection technique offers no benefit over a single injection for the performance of an ultrasound-guided supraclavicular block.