EFFECTS OF LIDOCAINE AND CALCITONIN-GENE-RELATED PEPTIDE (CGRP) ON ISOLATED HUMAN RADIAL ARTERIES

Vasoconstriction during and after microsurgery may cause hypoperfusion and result in flap necrosis. This study investigated the vascular eff ects of two known vasodilators: lidocaine and the naturally-occurring substance, calcitonin gene-related peptide (CGRP). Experiments were pe rformed in vitro on 47 human radial arterial rings from 18 patients un dergoing reconstruction after head and neck tumor surgery with free ra dial forearm flaps. Lidocaine produced a biphasic dose-response curve, with contraction at low concentrations (1.5 x 10(-5) to 1.5 x 10(-3) M) and relaxation at higher concentrations (4.5 X 10(-3) to 1.5 x 10(- 2) M). It caused significantly stronger contractions in arteries with mechanically removed endothelium, compared with arteries with intact e ndothelium. Prolonged rebound contraction occurred when the lidocaine concentration was decreased. Lidocaine also potentiated noradrenaline- induced contraction. CGRP produced only dose-dependent relaxation of c onstricted radial arteries at low concentrations (3 x 10(-10) to 10(-7 ) M). The contractile effects of lidocaine should be considered when a vasodilative substance is required.