Hemodynamic effects of normovolemic polycythemia in dogs at rest and during exercise

Abstract

The hemodynamic effects of acutely induced normovolemic polycythemia were studied in 4 anesthetized and 7 un-anesthetized dogs at rest and, in 3 of the latter, during treadmill exercise. Control observations were made in 4 other animals. Volume of packed red cells values of 60-79% were produced by exchange transfusion with washed centrifuged red cells. Normovolemic polycythemia in both anesthetized and unanesthetized resting animals was associated with a decrease in cardiac output and oxygen transport; little change in pulmonary artery, carotid artery, right atrium, and pulmonary artery wedge pressures; and increases in calculated total systemic and pulmonary vascular resistances. Mixed venous oxygen saturation was not necessarily reduced. The relative increase in cardiac output and oxygen transport in response to exercise was similar before and after normovolemic polycythemia, but the absolute increments were significantly less after normovolemic polycythemia. Results obtained are consistent with the concept that cardiac output reduction with normovolemic polycythemia is mediated by increased peripheral resistance.