Anesthesia (12)

A deltoid motor response is a satisfactory endpoint for successful block. (Columbia Presbyterian Medical Center, New York, NY) Reg Anesth Pain Med 2000;25:356–359.This study investigates the notion that a deltoid twitch may be just as effective as one in the biceps for predicting a successful motor block. Patients (N = 160) scheduled for shoulder surgery were studied prospectively. Interscalene blocks (ISBs) were performed using neurostimulation according to our standard technique. Twitches of the deltoid or biceps or both, whichever appeared first, were accepted and used as the endpoint for needle placement and injection of local anesthetic. Motor block success, i.e., patient inability to lift the arm against gravity, and minutes to motor block onset were recorded. Of the 160 ISBs performed, a biceps twitch was elicited in 61 patients. In 54 patients, a deltoid twitch was elicited and in 45 patients, both a biceps and deltoid contraction were elicited simultaneously. The failure rate did not differ widely among the groups; there was 1 failed motor block in the deltoid group and none in the other groups. There was no statistically significant difference in onset times between the 3 muscle twitch groups. Conclude that a deltoid twitch is as effective as a biceps twitch in determining accurate needle placement for ISB and in predicting successful motor block. Acceptance of a deltoid twitch during ISB eliminates the need for further probing and may translate into better patient acceptance and in a smaller risk of needle‐induced nerve damage. Comment by Alan David Kaye, MD, PhD.Interscalene brachial plexus block provides a valuable technique for shoulder surgery. The literature is in agreement with elicitation of paresthesias versus peripheral nerve stimulation. The literature is somewhat unclear regarding deltoid muscle versus biceps twitch as a satisfactory endpoint, prior to injection of local anesthetic. This prospective study involved 160 patients presenting for elective shoulder surgery. A biceps twitch was elicited in 61 patients; 54 had a deltoid twitch, and in 45 patients, both a biceps and deltoid twitch were elicited. There was no statistically different onset time in the 3 groups; however, the failure rate did not differ in the 3 groups either (only 1 patient in the deltoid group had a failed block). The authors conclude that a deltoid twitch is as effective as one in the biceps at ensuring a successful interscalene brachial plexus block and that repositioning is not warranted if either muscle group is elicited. The authors should be applauded for this study because it strongly suggests that essentially any elicitation of deltoid or biceps twitch will result in a highly successful and clinically useful block.