Systemic oxygen transport in induced normovolemic anemia and polycythemia

Abstract

The hemodynamic effects of normovolemic anemia and polycythemia were studied in 14 dogs. Anemia (5 dogs) and polycythemia (5 dogs) were induced by bleeding and simultaneously infusing dextran or packed erythrocytes. Measurements included cardiac output, arterial oxygen saturation, peripheral vascular resistance, and systemic oxygen transport (cardiac output X arterial oxygen content). Cardiac output had a significant negative linear relationship to hematocrit (r = –0.74, P < 0.01) over the range studied (13–74%). Peripheral resistance fell 46% in anemic animals and increased 152% in four of five polycythemic animals. Arterial saturation was significantly correlated to changes in hematocrit (r = 0.62, P < 0.01) and cardiac output (r = –0.55, P < 0.01); these values were due primarily to the linearity encountered in the anemia experiments and a reversal in these relationships tended to occur at high hematocrits. Systemic oxygen transport was maximum at normal hematocrits and decreased in anemia and polycythemia. The data indicate that hemodynamic adjustments in normovolemic anemia and polycythemia are insufficient to maintain normal oxygen delivery.