Effects of increasing the dose of ropivacaine on vertical infraclavicular block using neurostimulation

BACKGROUND: Use of an infraclavicular block is appropriate for surgery of the upper limb. However, it does not consistently block the entire brachial plexus. The aim of this study was to investigate whether increasing the dose of ropivacaine could enhance the success rate, onset time, and efficacy of the sensory and motor block during the use of a vertical infraclavicular block using neurostimulation in upper limb surgery. METHODS: Two hundreds and ten patients were prospectively randomized into three groups: Group 1 (30 ml of 0.5% ropivacaine; n = 70), Group 2 (40 ml of 0.5% ropivacaine; n = 70), and Group 3 (40 ml of 0.75% ropivacaine; n = 70). Patients in each group received a vertical infraclavicular block using neurostimulation and obtained a distal motor response of the ulnar or median nerve. Recorded outcome measures included block success rate, onset time, sensory and motor blocks, and adverse events. RESULTS: No differences were found in the block success rate among the three groups (92.8%, 97.1%, and 94.2% for Groups 1, 2, and, 3, respectively; P = 0.346). There were no significant differences in onset time (P = 0.225) among groups, nor was there enhancement in the sensory block, but the motor block was enhanced. Local anesthetic toxicity was observed in five female patients from group 3 (P = 0.006). CONCLUSIONS: Although the efficacy of the motor block was significantly improved, success rate, onset time, and efficacy of sensory block were not enhanced significantly among groups despite differences in volume and volume/concentration of the local anesthetic.