Vascular responses to anaesthetic agents.

Data have been presented showing that certain general anaesthetic agents such as halothane decrease the spontaneous activity of the rabbit anterior mesenteric portal vein and decrease the response of venous and aortic strips to exogenous noradrenaline. If these observations can be extrapolated to the intact animal they may indicate that the hypotension occurring with use of such agents may be due not only to cardiac effects but also to peripheral vasodilatation and muting of reflex sympathetic vasoconstriction. Although the response to noradrenaline is antagonized, this appears to be nonspecific effect and no evidence was found for interference with noradrenaline release nor for direct actions on beta-adrenegic receptors. While the thiobarbiturates increased spontaneous activity and tone of the rabbit anterior portal vein no evidence was obtained that this occurred through release of noradrenaline from tissue stores.