Although an ultrasound-guided brachial plexus block has become the standard, conventional brachial plexus blocks with a paresthesia or muscle twitch are still performed. However despite eliciting a paresthesia or muscle twitch, there are some cases in whom the brachial plexus block fails. This has been attributed to the difference between the proximal response (PR) and distal response (DR). Therefore, this study compared a supraclavicular block showing a PR with that showing a DR. In addition, clinical data such as success rate, onset time, and complications were examined.

Eighty three patients received a supraclavicular block with a nerve stimulator. All blocks were performed with 1% mepivacaine 40 ml. The subjects were divided into two groups-Group PR (n = 20, contraction of triceps or biceps) and Group DR (n = 63, flexion or extension of wrist or fingers) according to the types of muscle twitch. The success rate, onset time, and complications were measured and evaluated.

The success rate of Group DR (93.7%) was higher than that of Group PR (75.0%) (P < 0.05). The onset times of Group PR and DR were 15.3 ± 6.7 min and 14.4 ± 6.0 min, respectively.

The elicitation of a DR was more effective in increasing the success rate and reducing the onset time than the elicitation of a PR in a single-injection supraclavicular block.