Regional circulatory responses to alcohol and its congeners

The circulatory responses to ethyl alcohol are quantitatively related to the route and rate of administration as well as to the dose and the time of physiological measurements. A variety of acute regional blood flow responses have been described in the basal state in animals without prior exposure to ethanol. Gastric mucosal blood flow is substantially increased by ethanol. Pancreatic blood flow, on the other hand, has been found to undergo a dose-dependent reduction. Hepatic blood flow has been found to increase in baboons without evidence of ischemia. Renal arteries appear to be unresponsive up to 3 g/kg. Similarly, the cerebral vasculature does not seem to be affected by ethanol except at high dose levels where increased flow occurs. Animal studies, however, have suggested that ethanol may interfere with autoregulation. In terms of limb blood flow, oral administration has been found to enhance flow to the skin but to diminish skeletal muscle blood flow. Vasodilatation of the coronary vasculature has been consistently reported to be significantly greater in animals than in humans. The major metabolite of ethanol, acetaldehyde, has significant effects on circulation. At blood levels achieved after feeding ethanol, there was a 60% rise of coronary blood flow but myocardial oxygen consumption was reduced, presumably representing a shunting effect in myocardium.