Differential vascular reactivity of canine mesenteric arteries and veins to sevoflurane

Purpose. The aim of this study was to compare the vascular reactivities of canine mesenteric arteries and veins to sevoflurane and to elucidate the underlying mechanism that is responsible for sevoflurane-induccd hypotension. Methods. Vascular rings of canine mesenteric arteries and veins were suspended in organ baths, and the effect of 2.3% and 4.6% sevoflurane on the contractile responses to transmural electrical stimulation (ES) and to norepinephrine (NE) were determined by recording isometric tension changes. The rings were contracted to a stable tension by the addition of NE and then exposed to increasing concentrations of sevoflurane (0%-5.1%). Results. Sevoflurane attenuated the contractile responses to transmural ES in veins but not in arteries. The concentration responses to NE were not affected by sevoflurane in arteries or in veins. At stable precontraction induced by NE, when sevoflurane was placed in the bathing medium, arteries with intact endothelium had significant contraction at 1.7% and 3.4% sevoflurane, followed by relaxation at 5.1%. On the contrary, sevoflurane produced dose-dependent relaxation in endothelium-denuded arteries and endothelium-intact veins. Conclusion. It is suggested that the relaxation of the veins by sevoflurane may be due to the inhibition of NE release from sympathetic nerve endings and to the direct inhibition of the contractile mechanisms of vascular smooth muscle. In arteries, sevoflurane causes endothelium-dependent vasocontraction, probably by inhibiting the release of basal endothelium-derived relaxing factor (EDRF).