Introduction to the Anesthetic Agents

Abstract

The intravenous administration of most anesthetics, in sufficient dosage to result in a surgical plane of anesthesia, is known to induce peripheral vasodilation and hypotension in mammals. There is increasing in vitro and in vivo evidence that, in the microcirculatory system, these dosages can exert direct depressant and vasodilator effects on vascular smooth muscle. Anesthetic agents appear to be able to; 1) directly inhibit vascular smooth muscle vasomotion, and 2) nonspecifically depress the vascular smooth muscle contractile response to a variety of neurohumoral substances and certain ions. This depressant activity seems to be related to the movement and/or translocation of Ca++ across the vascular membranes and intracellularly. There is some evidence that venous smooth muscle cells are more sensitive to these agents than are arterial smooth muscle cells.¹ Smaller (20 micron diameter) arterioles tend to be more profoundly affected than larger arterioles. Influences on the microvascular beds tend to be both dose-dependent and tissue-specific.²