Sonographic Guidance for Supraclavicular Brachial Plexus Blocks: Single vs. Double Injection Cluster Approach.

BACKGROUND The cluster approach for supraclavicular brachial plexus block (SC-BPB) can be easily performed but may result in asymmetric local anesthetic (LA) spread. The authors hypothesized that the use of a cluster approach in each of the 2 planes would achieve better 3-dimensional LA distribution than the traditional single cluster approach. OBJECTIVES The purpose of the present study was to compare a double injection (DI) in 2 planes (one injection in each plane) with the traditional single injection (SI) cluster approach for ultrasound-guided SC-BPB. STUDY DESIGN A randomized, controlled trial. SETTING Department of Anesthesiology and Pain Medicine, Gachon University Gil Medical Center. METHODS In the SI group (n = 18), 30 mL of LA was injected into the main neural cluster after penetrating the brachial plexus sheath laterally. In the DI group (n = 18), the needle penetrated the sheath in a downward direction at the first skin puncture, and 15 mL of LA was injected, and at the second skin puncture (behind the initial puncture site), the needle penetrated the sheath in an upward direction, and 15 mL was again injected. Ultrasound-guided SC-BPB was evaluated from immediately after the block every 5 minutes to 30 minutes by sensory and motor testing. The main outcome variables were procedural time; onset time (time for complete sensory and motor block of the median, radial, ulnar, and musculocutaneous nerves); and rate of blockage of all 4 nerves. RESULTS Procedure times (medians [interquartile range]) were similar in the DI and SI groups (5.5 [4.75 - 8] vs. 5 [4 - 7] minutes, respectively; P = 0.137). Block onset time in the DI group was not significantly different from that in the SI group (10 [5 - 17.5] vs. 20 [6.25 - 30] minutes, P = 0.142). However, the rate of blockage of all 4 nerves was significantly higher in the DI group (94% vs. 67%, P = 0.035). LIMITATIONS Although the results of this study indicate LA distribution in the DI group was more evenly spread within brachial plexus sheaths than in the SI group, this was not confirmed by ultrasonography or contrast radiography. CONCLUSION The DI approach can be performed easily as single cluster approach and increases the consistency of ultrasound-guided SC-BPB over the SI approach in terms of the rate of blocking of all 4 nerves. Key words: Brachial plexus block, corner pocket approach, cluster approach, multiple injection, supraclavicular block, ultrasound.