Regional vascular changes during hypotensive anesthesia

Abstract

The regional vascular effects of three different hypotensive drug treatments were compared in enflurane anesthetized rats. Controlled hypotension was induced with sodium nitroprusside (SNP), nitroglycerin (NTG),and deep enflurane anesthesia. Regional blood flow was measured during each hypotensive treatment using radioactive microspheres. All hypotensive treatments were compared with control rats, anesthetized with 2% inspired enflurane anesthesia. Results indicate that when the mean blood pressure was decreased from 124 to 70 torr with all three hypotensive treatments regionally specific blood flow changes occurred. These ranged from approximately 50% decreases seen in skin blood flow with all hypotensive drugs to 50-90% increases in flow in muscle and spleen tissues. When regional vascular resistance changes were compared between hypotensive drug treatments, SNP produced significantly less cerebrovasodilation than either NTG or deep enflurane. Deep enflurane induced hypotension resulted in significantly greater decreases in intestinal vascular resistance than either SNP or NTG. These results indicate that hypotensive anesthesia with SNP, NTG, or deep enflurane shift blood flow away from skin and toward skeletal muscle and spleen tissues. Blood flow in other tissues is relatively well maintained.