Topical anesthetic before microneurography decreases pain without affecting sympathetic traffic

Pain associated with the microneurography procedure varies among human rese arch volunteers, and may influence baseline sympathetic neural activity. Th e purpose of this study was to evaluate the efficacy and effects of applyin g a topical anesthetic prior to microneurography. Ten volunteers underwent microneurography twice, separated by a minimum of 4 weeks. Using a single-b lind, randomized cross-over design, EMLA cream (2.5% lidocaine and 2.5% pri locaine 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 (extr eme pain). The electrocardiogram, and efferent sympathetic nerve traffic fr om peroneal nerve muscle fascicles at the popliteal fossa were recorded dur ing a 10-min supine rest period. EMLA cream significantly reduced perceptio n of pain (P<0.05), but did not affect burst reflex latencies from precedin g R-waves or total muscle sympathetic nerve traffic (P>0.05). These data sh ow that use of EMLA cream prior to microneurography is innocuous, and do no t support the hypothesis that baseline sympathetic traffic is increased by pain or discomfort associated with microneurography. (C) 2000 Elsevier Scie nce B.V. All rights reserved.