The Circulatory Adjustments to Posthemorrhagic Anemia in Dogs

Several measures of cardiovasculitr function were made in nine dogs before, during, and after the production of anemia by daily venesections. Stress is laid on the time sequence of the various changes in the circulation and their relation to each other. From the results obtained it was con-cluded that the elevated cardiac output observed in anemia was not the result of an increase in right atrial pressure or a decrease in tissue oxygen tension, per se. It is suggested that the increased cardiac output may be due to a slowly elaborated or slow-acting humoral agent produced as a result of tissue anoxia. THE various cardiovascular adjustmentswhich occur in anemia are well de-scribed.1 Less is known about the time relationships of these changes during the development of the anemia and during treat-ment. Further, the mechanism responsible for the compensatory elevation in cardiac output has not been clarified. This paper is concerned Avith an investigation of these points in dogs made anemic by daily bleedings. METHOD The following cardiovascular measurements and calculations were made in nine dogs before, during and after the production of anemia by venesections of approximately 100 to 200 cc. per day for six to eight clays. All observations were made with the dogs anesthetized with sodium pentobarbital. An initial dose of 30 mg. per kilogram was given intravenously followed by 60 to 120 mg. intramuscularly every one to two hours, as necessary. The cardiac output was determined by the direct Fick technic. The oxygen content of arterial and mixed venous blood (right ventricle) was determined by the method of Peters and Van Slyke.2 Oxygen consumption was measured with a Benedict-Roth type of spirometer. Mean pressures from the right atrium were measured with a cardiac catheter con-nected to a saline manometer and from a peripheral artery through an inlying needle connected to a mercury manometer. The heart rate was counte