Patients' perception of pain during axillary and humeral blocks using multiple nerve stimulations

Axillary or humeral blocks by multiple nerve stimulation (MNS) are used for ambulatory hand surgery. This double-blind study identified which of the three main components of the procedure (repeated needle passes, local anesthetic injections, or electrical stimulations) is most painful, quantified its intensity, and recorded patients' preferences for a future anesthetic.

Eighty unsedated ambulatory patients were randomized to 2 equal groups: axillary (A) and humeral (H). In each patient, 4 terminal motor nerves (musculocutaneous, median, ulnar, and radial) were electrolocated by use of an initial current of 2 mA, 0.1 ms and a target current of 0.1 to 0.5 mA. After block placement and before the start of surgery, patients were requested to identify which of the 3 main components of the block was most unpleasant and to quantify its intensity on a visual analog scale (VAS) of 0 to 100. Twenty minutes after completion of the block, the unblocked nerves were electrolocated at the elbow and supplemented. Patients were declared ready for surgery when they had complete analgesia of the hand and forearm. Before discharge from the hospital, patients indicated which anesthetic method (block alone, block plus sedation, or general anesthesia) they would choose for future hand surgery.

Twenty-seven patients in group A vs. 17 patients in group H reported electrical stimulations as the most unpleasant block component (P =.03). No significant differences occurred in any of the VAS scores. Patients' request for the same anesthetic, 35 in group A and 37 in group H, were similar. Group A patients were ready for surgery sooner than group H patients (mean 26 minutes vs. mean 30 minutes for group H patients; P =.04). No serious complications were observed.

This study found that more axillary-block patients compared with humeral-block patients reported electrical stimulation as the most unpleasant part of the block but failed to detect significant differences in the intensity of the 3 block components (repeated needle passes, local anesthetic injections, and electrical stimulations). Most patients in both groups would accept the same block for future hand operations. Patients were ready for surgery sooner after axillary block, but the clinical importance of this finding is doubtful.