The effects of arm position on central spread of local anesthetics and on quality of the block with axillary brachial plexus block.

ABSTRACT

BACKGROUND AND OBJECTIVES: Spread of local anesthetic solution in axillary brachial plexus block is thought to be influenced by the position of the arm and the use of compression maneuvers. We investigated how these two factors affected central local anesthetic spread and block quality. METHODS: Radiographic spread of local anesthetic was studied in 80 adult patients. They received mepivacaine mixed with contrast agent through an indwelling catheter with the arm abducted to either 0 or 90 degrees , and with or without local digital compression. Central and peripheral spread of the contrast agent was evaluated with anteroposterior radiographs of the axilla. Block quality was studied in a separate series of 70 adult patients. They received mepivacaine with the arm abducted 0 degrees or 90 degrees . The degree of sensory and motor block was assessed 20 minutes after the injection. RESULTS: Arm position at 0 degrees abduction promoted central spread of the contrast agent. Although digital compression suppressed peripheral spread effectively, it did not improve the central spread of the solution. Sensory block was comparable in all terminal nerves of the arm in both arm positions, whereas motor block of the radial nerve was promoted with no abduction. CONCLUSIONS: The central spread of local anesthetics is facilitated by injection without abduction of the arm but not by the use of compression at the injection site. This, however, did not alter the quality of the block.