The hemodynamic response to isoflurane is altered in genetically hypertensive (SHR), as compared with normotensive (WKY), rats.

The authors compared the hemodynamic effects of isoflurane anesthesia in normotensive (WKY) and genetically hypertensive (SHR) rats. Eighteen male SHR and 18 WKY rats were subdivided into conscious animals and those anesthetized with isoflurane, 1.2 vol% inspired. During brief isoflurane anesthesia, cannulae were placed in the left cardiac ventricle, the femoral artery, and the femoral vein. Central and regional hemodynamics were determined with 85Sr-labeled microspheres (15 +/- 1 micron) using the reference sample technique in both conscious and anesthetized animals. Isoflurane anesthesia caused similar reductions in mean arterial blood pressure (MAP) in all rats. This was due to a significant decrease in systemic vascular resistance in WKY rats, whereas MAP declined due to a significant decrease in cardiac output in SHR rats. In the anesthetized WKY rat, the decrease in total systemic vascular resistance resulted from significant decreases in vascular resistance of the brain and nonrespiratory skeletal muscles. In the anesthetized SHR rat, both decreases (cerebellum, hepatic artery) and increases (GI tract, skin, diaphragm) in regional vascular resistances occurred, resulting in no net change in total systemic vascular resistance. In both SHR and WKY rats, isoflurane redistributed blood flow in favor of the brain at the expense of blood flow to the GI tract, diaphragm, and skin. Blood flows to the liver, GI tract, and skin were significantly less in the anesthetized SHR as compared with WKY rats. It is concluded that isoflurane influences central and regional hemodynamics differently in hypertensive, as compared with normotensive, rats.