Myocardial Blood Flow and Oxygen Uptake during Acute Red Cell Volume Increments.

• Changes in vascular tone and pressure gradients have been established as important factors in the control of regional blood flow, but the influence of varied physical states of the perfusing blood is less clear. In a hemodynamic evaluation of shock, Seligman indicated that enhanced blood viscosity promoted the onset of irreversibility, presumably through an effect on flow. More recently Richardson assigned a major role to viscosity in the development of a diminished cardiac output during acute normovolemic polycythemia.