Double-injection method using peripheral nerve stimulator is superior to single injection in axillary plexus block

BACKGROUND AND OBJECTIVES: Axillary block using a single-injection method does not always provide effective analgesia. This study examined whether a double axillary block injection technique is superior to a single injection axillary block. METHOD: Fifty patients were randomly allocated to two groups. In group I (single injection), the whole volume of local anesthetic (0.7 mL/kg) was injected after locating only one of the median, radial, or ulnar nerves. In group 2 (double injection), half of the volume was injected after locating one nerve and the other half after locating another peripheral nerve. Bupivacaine 0.5% and prilocaine 1% (1:1 volumes) were used as local anesthetic. A peripheral nerve stimulator was used to identify the nerves. Sensory block of seven nerves and motor block of four nerves were tested after 40 minutes. RESULTS: Complete sensory and motor block (scores 2 or 3 on scale 0-3) in all four main nerves (median, ulnar, radial, musculocutaneous) was achieved in 3 (12%) versus 20 (80%) patients in groups 1 and 2, respectively (P = .000001). Primary success rate (no need for supplemental nerve block) was 52% in group 1 and 92% in group 2 (P = .0016). CONCLUSIONS: A double-injection method in axillary block provides excellent analgesia and motor block compared with a single-injection method. Moreover, the need for supplemental nerve blocks is significantly decreased.