Hemodynamic Consequences of Induced Changes in Blood Volume

Abstract

The effects of transfusion or bleeding on cardiac output and blood pressure have been followed for periods of seven to ten hours in trained, conscious dogs. When blood volume is increased by transfusion of blood, supplemented by dextran to minimize the expected change in hematocrit, cardiac output and blood pressure increase initially. After one and one-half hours the cardiac output returns to the initial level but blood pressure remains elevated and calculated peripheral resistance increases. This state has been maintained for a period of ten hours by repeated transfusion. After bleeding, with replacement of packed cells, again to minimize the change in hematocrit, cardiac output decreases initially and peripheral resistance increases, but after three hours, output returns to its former level, and peripheral resistance falls below the control value. These changes become more prominent when a second hemorrhage is performed two hours after the first one. The reduction of resistance was then maintained for seven hours. These findings demonstrate that the effects of changes in blood volume are not limited to the acute changes in cardiac output and filling pressure. After periods of one to three hours, changes in peripheral resistance also become evident.