Kinetics of elimination of glucose from the blood during and after a continuous intravenous injection

The glucose tolerance tests in routine clinical use are predominantly of the oral type, in which the sugar is administered by mouth. Such tests, however, suffer from the disadvantage that the rate of intestinal absorption has an effect on the results, and its variations may entirely overshadow any possible changes in carbohydrate metabolism. This difficulty may, of course, be obviated by ad-ministering the sugar by vein, and intravenous tolerance tests have actually been used by many workers (1-8).2 In these tests the sugar has gen-erally been given as a single rapid injection. While such a method undoubtedly gives useful informa-tion, it can hardly be regarded as a quite physio-logical one. A more natural procedure would be to inject glucose slowly over a long period of time, thus imitating the normal process of absorp-tion. So far, tolerance tests of this type have ap-parently received scant attention. As it seemed that this method might provide additional informa-tion not easily obtainable from the tests based on a single rapid injection, we decided to carry out the following experiments, in which glucose was administered as a continuous injection of constant rate and of relatively long duration. METHODS Our subjects were hospitalized patients. During the experiments they were in the postabsorptive state. Ap-proximately isotonic (5 to 6 per cent) glucose solutions in distilled water were used, and their glucose content was determined by polarimetry. The sterilized glucose solution was run by gravity from the infusion apparatus into the cubital vein. The rate of infusion was kept as nearly constant as possible. It was checked at frequent intervals by means of a drop-counting device and readjusted if necessary. The infu