Abstract
At the last meeting of the American Physiological Society some experiments were reported on the effects of hemorrhage on the response to a gradual reduction in the percentage of oxygen in the respired air. These experiments were performed on the normal unanesthetized dog connected by means of a mask with a rebreathing apparatus arranged to absorb the carbon dioxide of the expired air as the oxygen was consumed. The purpose of the experiments was to determine the detrimental effects of hemorrhage and the subsequent effects of replacing the lost blood with a gum-saline solution.
We reasoned that if a normal percentage of hemoglobin and a normal flow of blood are essential for a normal gaseous exchange, that the response of an animal to a reduction in the percentage of oxygen in the respired air would be altered by hemorrhage; and further that if the intravenous injection of gum-saline accelerated the volume-flow of blood out of proportion to the accompanying dilution, the reduced tolerance to low pressures of oxygen would be improved.
To our surprise we were unable to detect, with the methods employed, any decrease in tolerance after hemorrhage amounting to 3 per cent. of the body weight. We do not attempt to definitely explain these results as yet, but wish to point out a striking effect of hemorrhage. It invariably produced a quieting effect upon the dogs accompanied by a softness of muscle indicative of a marked reduction in muscular tonus. It is possible that the decreased demand for oxygen on the part of the tissues partly explains our data.
When carbon dioxide was allowed to accumulate in the re-breathing apparatus as the oxygen percentage of the respired air decreased, hemorrhage produced a definite decrease in tolerance to the combined changes in carbon dioxide and oxygen.
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