COMPARISON OF VASCULAR EFFECTS OF ROPIVACAINE AND LIDOCAINE ON ISOLATED RINGS OF HUMAN ARTERIES

Ropivacaine is a new local anaesthetic agent. Previous animal studies have indicated that vasoconstrictor effects are elicited by ropivacain e in vitro and subcutaneously and that it produces blanching of the sk in if injected subcutaneously in humans. Lidocaine is a widely used lo cal anaesthetic reported to exert a biphasic effect on the microvascul ature with contraction at low concentrations and relaxation at high co ncentrations. There is a need for pharmacologic tools able to countera ct local arterial vasoconstriction. In this study, the contractile eff ect of ropir;acaine and lidocaine were investigated in vitro on isolat ed human arteries. Experiments were performed on 43 internal mammary a rtery (IMA) rings obtained from 22 patients and on 14 radial artery (R A) rings from 7 patients. The rings were mounted in organ baths and is ometric contractile activity was measured. Experiments were conducted by cumulative adding ropivacaine or lidocaine (1.5x10(-5) M; 4.5x10(-5 ) M; 1.5x10(-4) M; 4.5x10(-4) M; 1.5x10(-3) M; 4.5x10(-3) M; 1.5x10(-2 ) M) to the organ baths. The endothelium was mechanically removed in 1 9 IMA rings and in 9 RA rings. Ropivacaine and lidocaine produced a bi phasic response with contraction at low concentrations (1.5x10(-5)-1.5 x10(-3) M) and release of the maximal contraction at higher concentrat ions. No statistically significant differences in contractile or relax ing effects were seen between the two drugs. Removal of the endotheliu m did not significantly affect contractile activity. In this study of human mammary artery preparations, ropivacaine is not a stronger vasoc onstrictor than lidocaine.