AJP - Heart and Circulatory Physiology, Vol 256, Issue 2 472-H477, Copyright © 1989 by American Physiological Society
Optimal hematocrit for canine gastric oxygenation
J. W. Kiel and A. P. Shepherd
Department of Physiology, University of Texas Health Science Center, San Antonio 78284.
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.
