Effect of arm position on the effectiveness of perivascular axillary nerve block.

The influence of arm position on the effectiveness of perivascular axillary nerve block with a catheter was assessed prospectively in two groups of patients. Ninety patients were allocated randomly to receive 1% mepivacaine with adrenaline 40 ml with the arm either adducted or abducted. Radiographs were taken in 12 additional patients; six in each group immediately after injection of 2% mepivacaine 20 ml mixed with contrast agent 20 ml. There were no statistically significant differences in onset time, spread of analgesia, motor block or success rate between the two groups. Proximal flow of the local anaesthetic-contrast agent mixture was neither facilitated by arm adduction nor was it necessary for the development of a successful block.