Infraclavicular brachial plexus block: Comparison of posterior cord stimulation with lateral or medial cord stimulation, a prospective double blinded study

BACKGROUND: Infraclavicular approach to the brachial plexus sheath provides anesthesia for surgery on the distal arm, elbow, forearm, wrist, and hand. It has been found that evoked distal motor response or radial nerve-type motor response has influenced the success rate of single-injection infraclavicular brachial plexus block. AIM: We conducted this study to compare the extent and effectiveness of infraclavicular brachial plexus block achieved by injecting a local anesthetic drug after finding specific muscle action due to neural stimulator guided posterior cord stimulation and lateral cord/medial cord stimulation. METHODS: After ethical committee approval, patients were randomly assigned to one of the two study groups of 30 patients each. In group 1, posterior cord stimulation was used and in group 2 lateral/medial cord stimulation was used for infraclavicular brachial plexus block. The extent of motor block and effectiveness of sensory block were assessed. RESULTS: All four motor nerves that were selected for the extent of block were blocked in 23 cases (76.7%) in group 1 and in 15 cases (50.0%) in group 2 (P:0.032). The two groups did not differ significantly in the number of cases in which 0, 1, 2, and 3 nerves were blocked (P>0.05). In group 1, significantly lesser number of patients had pain on surgical manipulation compared with patients of group 2 (P:0.037). CONCLUSION: Stimulating the posterior cord guided by a nerve stimulator before local anesthetic injection is associated with greater extent of block (in the number of motor nerves blocked) and effectiveness of block (in reporting no pain during the surgery) than stimulation of either the lateral or medial cord.