Different sensory blockade of interscalene versus axillary approach of brachial plexus block

We examined results of brachial plexus block in 31 young male patients who underwent upper extremity surgical procedures. Interscalene block was performed using a paresthesia technique in 13 patients and axillary block, using the perivascular technique, in 18 patients. In both groups, 30 ml 1.5% lidocaine with 1:200,000 epinephrine was injected. Sensory blockade was evaluated at 5 min and 15 min after injection, determined by pinprick. Results showed that the interscalene technique preferentially blocked the cephalad nerves while the axillary technique produced similar block of both cephalad and caudal nerves of the brachial plexus. Difference between groups was statistically significant, suggesting that the extent of nerve block depends on the technique of approach per se. The difference in patterns of nerve blocked by either technique could be due to the access of local anesthetic to the different components of plexus in the sheath.