Optimal hematocrit for canine gastric oxygenation.

To determine whether an optimal hematocrit exists at which gastric tissue is maximally oxygenated, chambered segments of resting canine stomach were perfused at a constant pressure while hematocrit was decreased in steps from 60 to 10%. The two groups of animals used were a control group and a second group given pentagastrin to elevate metabolic activity. Total blood flow was inversely related to hematocrit in both the control and pentagastrin-treated animals, and arteriovenous oxygen difference was directly related to hematocrit. Consequently, the relationship between gastric oxygen consumption and hematocrit was parabolic in both groups. Therefore, the oxygen uptake vs. hematocrit data from each experiment were fit to a quadratic equation that was used to calculate the maximal oxygen uptake and the optimal hematocrit for each preparation. Both the maximum oxygen uptake and the optimal hematocrit in the pentagastrin-treated group (2.1 +/- 0.4 ml.min-1.100 g-1 and 45.7 +/- 1.4%, respectively) were significantly greater than in the control group (1.5 +/- 0.4 ml.min-1.100 g-1 and 38.2 +/- 0.7%, respectively). We conclude that an optimal hematocrit exists for the oxygenation of gastric tissue and that it is within the normal hematocrit range under resting conditions. However, the optimal hematocrit is slightly higher than normal during periods of increased metabolic activity.