Topical anaesthesia does not affect cutaneous vasomotor or sudomotor responses in human skin

Abstract

(1) The effects of local sensory blockade (topical anaesthesia) on eccrine sweat glands and cutaneous circulation are not well understood. This study aimed to determine whether topical lidocaine/prilocaine alters eccrine sweat gland and cutaneous blood vessel responses. (2) Sweating (capacitance hygrometry) was induced via forearm intradermal microdialysis of five acetylcholine (ACh) doses (1 × 10(-4) to 1 × 10(0) m, 10-fold increments) in control and treated forearm sites in six healthy subjects. Nitric oxide-mediated vasodilatory (sodium nitroprusside) and adrenergic vasoconstrictor (noradrenaline) agonists were iontophoresed in lidocaine/prilocaine-treated and control forearm skin in nine healthy subjects during blood flow assessment (laser Doppler flowmetry, expressed as% from baseline cutaneous vascular conductance; CVC; flux/mean arterial pressure). (3) Non-linear regression curve fitting identified no change in the ED50 of ACh-induced sweating after sensory blockade (-1.42 ± 0.23 logM) compared to control (-1.27 ± 0.23 logM; P > .05) or in Emax (0.43 ± 0.08 with, 0.53 ± 0.16 mg cm(-2) min(-1) without lidocaine/prilocaine; P > .05). Sensory blockade did not alter the vasodilator response to sodium nitroprusside (1280 ± 548% change from baseline CVC with, 1204 ± 247% without lidocaine/prilocaine) or vasoconstrictor response to noradrenaline (-14 ± 4% change from baseline CVC with, -22 ± 14% without lidocaine/prilocaine; P > 0.05). (4) Cutaneous sensory blockade does not appear to alter nitric oxide-mediated vasodilation, adrenergic vasoconstriction, or cholinergic eccrine sweating dose-response sensitivity or responsiveness to maximal dose. Thus, lidocaine/prilocaine treatment should not affect sweat gland function or have blood flow implications for subsequent research protocols or clinical procedures.