Abstract

Lidocaine (or mepivacaine) was infused in rabbits first in the lower part of the aorta to provoke a direct effect on thigh skeletal muscle blood flow and later intravenously to produce a generalized circulatory effect. The effect on thigh muscle blood flow was evaluated by measurements of muscle surface oxygen tension (p_tO₂) with the help of the MDO electrode. Both mean values and types of histograms were studied. Our study shows that both local anesthetic agents tested produced a decreased skeletal muscle blood flow because of a vasocon-striction, when given into the aorta (most likely due to a direct stimulatory effect on the smooth muscles in peripheral vessels). In contrast, an intravenous infusion provoked an increased blood flow that indicated a vasodilation, an effect that could be explained by an increase in cardiac output and a decrease in systemic vascular resistance. Thus, the general circulatory effect of a local anesthetic seems to override a direct vasoconstrictor effect on the peripheral vessels.