Median versus musculocutaneous nerve response with single-injection infraclavicular coracoid block

Local anesthetic injection after elicitation of a distal motor response with a nerve stimulator is believed to produce a more clinically efficient infraclavicular coracoid block than after elicitation of a proximal motor response. The aim of this study was to investigate whether elicitation of a median or of a musculocutaneous-type nerve response influenced the quality of anesthesia.

Randomized, prospective, single-blind study. One hundred thirty patients received a coracoid block with 40 mL plain mepivacaine 1.5% after stimulation of median nerve fibers (group 1) or musculocutaneous nerve fibers (group 2). Patients were assessed for sensory and motor block at 5 and 20 minutes.

Significantly higher rates of complete anesthesia at 20 minutes were found in the cutaneous distributions of the radial and ulnar nerves in group 1. Significantly higher rates of complete paralysis were found for elbow extension, wrist flexion, and finger and thumb movements in group 1 at 20 minutes. Differences in the extent of anesthesia and paralysis were more remarkable at 5 minutes than at 20 minutes.

Elicitation of a median nerve response improved the efficacy of infraclavicular coracoid block when compared with a musculocutaneous nerve response. Complete paralysis and complete anesthesia of the upper limb were low in both groups.