Restricted infraclavicular distribution of the local anesthetic solution after infraclavicular brachial plexus block

Background and Objectives: The distribution of local anesthetic after different approaches for brachial plexus anesthesia could be responsible for the varying rates of side effects, such as phrenic block, hoarseness, and Horner's syndrome associated with each approach. We compared the distribution of local anesthetic within the neurovascular space in infraclavicular block with that of interscalene and supraclavicular block. Methods: In a prospective analysis using fluoroscopy, we studied the distribution of a solution of local anesthetic containing radiologic contrast medium in 18 patients. Six patients received an interscalene block, another 6 patients received a perpendicular supraclavicular block, and another 6 patients, a perpendicular coracoid block. Results: Distribution of the anesthetic solution in the interscalene and supraclavicular groups extended to both supraclavicular and infraclavicular spaces in all patients. This distribution was significantly different (P < .05) compared with that of the infraclavicular group. In this group, the solution remained below the clavicle in every patient. Conclusions: Spread of the local anesthetic from the infraclavicular space after infraclavicular coracoid block appears to be limited to below the level of the clavicle. Conversely, local anesthetic solution passes below the clavicle in all patients given interscalene or supraclavicular blocks.