Distribution volume of ethanol as a measure of body water

We compared the volumes of distribution of intravenous and intragastric ethanol, in a dose of either 7.7 or 11 mmol/kg, to the 3H2O space in anesthetized dogs. The intravenous ethanol space agreed closely with the 3H2O space (y = 0.197 + 0.974x; x axis 3H2O space, r = 0.967, n = 37). After acute saline infusion, changes in both intravenous ethanol and 3H2O spaces reflected accurately the volumes of infused isotonic saline. The determination of intravenous ethanol space could be repeated within 5 h. The intragastric ethanol space overestimated both the 3H2O space and the intravenous ethanol space. Incomplete absorption of ethanol from the gastrointestinal tract was the cause of this observation. In dogs, the intravenous ethanol space provides an accurate measure of body water and of its short changes (a few hours). The intragastric ethanol space overestimates body water in anesthetized dogs because of delayed gastrointestinal absorption.