MAGNITUDE OF SKIN VASOMOTOR REFLEX REPRESENTS THE INTENSITY OF NOCICEPTION UNDER GENERAL-ANESTHESIA

Because nociceptive stimuli induce the skin vasomotor reflex (SVmR), t he assessment of the SVmR would be a useful indicator to represent noc iception. We examined 39 adult patients for the relationship between t he magnitude of the SVmR and the intensity of nociceptive stimulus tha t induced the SVmR. Under oxygen-nitrous oxide (50%) and sevoflurane a nesthesia, the SVmR was induced by an electrical impulse to the ulnar nerve and detected by a laser Doppler flowmeter. Study 1: under the en d-tidal concentrations of sevoflurane at 1.2% (n = 10), 1.7% (n = 9) o r 2.2% (n = 10), the SVmR was tested by a 2-s, 50-Hz tetanic electrica l impulse with a current intensity changing (40, 50 or 60 mA) in a ran domized order. Study 2: under the end-tidal concentration of sevoflura ne at 1.7% (n = IO), the SVmR testing was performed with a 50-mA, 50-H z tetanic electrical impulse with the current duration changing (2, 3 or 4 s) in a randomized order. The studies demonstrated significant co rrelations of (I) the current intensity which induces the skin vasomot or reflex (SVmR) vs. the magnitude of the SVmR under the three differe nt anesthesia depths, (2) the anesthesia depth vs. the magnitude of th e SVmR (inverse proportion) under the same current intensity and (3) t he duration of electrostimulation vs. the magnitude of the SVmR. Thus, the SVmR could be helpful for the objective assessment of nociception and anti-nociceptive effects in individual cases. (C) 1998 Elsevier S cience B.V. All rights reserved.