Ratio of red cell velocities near the vessel wall to velocities at the vessel center in cerebral microcirculation, and an apparent effect of blood viscosity on this ratio

High speed microcinephotography of selected vessels on the cerebral surface revealed that, in normal mice, erythrocyte velocity at the center of the vessel (V_c) was about 30% greater than velocity near the vessel wall (V_w). The difference between V_w and V_c significantly decreased when blood viscosity was raised by high molecular weight dextran and increased significantly in anemia, as well as in anemic macroglobulinemic mice. These data suggest an in vivo relationship between rheologic factors, such as hematocrit, plasma viscosity and whole blood viscosity on the one hand, and the shape of the velocity profile on the other.