Dose‐related effects of isoflurane on superior mesenteric vasoconstriction induced by endotoxemia in the rat

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Abstract
To investigate the interplay between endotoxin‐induced circulatory shock and the cardiovascular effects of different doses of isoflurane, mean aortic pressure (MAP), central venous pressure (CVP), mean pulmonary arterial pressure (MPAP), heart rate (HR), cardiac output and superior mesenteric artery flow (SMAF), were monitored in rats anesthetized with either 1.4% or 2.0% isoflurane in oxygen. Cardiac index (CI), total peripheral vascular resistance (TPR) and superior mesenteric vascular resistance (SMVR) were derived. During continuous administration of isoflurane, endotoxin (LDW90, 40 mg·kg‐1iv) was given after a 30‐min baseline period, and data were collected for an additional 2‐h period. Sham‐challenged (saline) animals served as controls. The response to endotoxin in the systemic circulation showed a decrease in CI and MAP, while HR and TPR increased. MAP and CVP were essentially unchanged. There were no significant differences in thesystemiccirculation variables between endotoxin groups, apart from a more pronounced HR increase during 1.4% isoflurane.Regionally, however, SMAF was lower and SMVR was higher in the 2.0% versus the 1.4% isoflurane group following endotoxin. To conclude, the degree of mesenteric vasoconstriction during endotoxemia was dependent on the dose of isoflurane. This dose‐related effect seems to be mediated through interaction with intrinsic vascular control, a higher dose allowing a more pronounced local blood flow reduction.