Topical anesthetic before microneurography decreases pain without affecting sympathetic traffic

Pain associated with the microneurography procedure varies among human research volunteers, and may influence baseline sympathetic neural activity. The purpose of this study was to evaluate the efficacy and effects of applying a topical anesthetic prior to microneurography. Ten volunteers underwent microneurography twice, separated by a minimum of 4 weeks. Using a single-blind, randomized cross-over design, EMLA cream (2.5% lidocaine and 2.5% prilocaine in oil emulsion) or an aqueous placebo cream was applied 2 h prior to each session. Subjects rated pain on a scale from 0 (no pain) to 4 (extreme pain). The electrocardiogram, and efferent sympathetic nerve traffic from peroneal nerve muscle fascicles at the popliteal fossa were recorded during a 10-min supine rest period. EMLA cream significantly reduced perception of pain (P < 0.05), but did not affect burst reflex latencies from preceding R-waves or total muscle sympathetic nerve traffic (P > 0.05). These data show that use of EMLA cream prior to microneurography is innocuous, and do not support the hypothesis that baseline sympathetic traffic is increased by pain or discomfort associated with microneurography.