The effect of polycythemia on blood flow in working and non-working skeletal muscle

The effect of acutely induced polycythemia on blood flow and viscosity in the vasodilated vascular bed of working and non-working skeletal muscle was studied. In 12 mongrel dogs anesthetized with thiopental sodium the calf muscle of one hind limb was isolated. Vasodilation was induced either by sciatic stimulation setting the muscle at maximal work or by i.a. infusion of papaverine. Blood flow was measured at different perfusion pressure before and after infusion of 300 ml packed homologous red cells. Blood viscosity in vitro was determined in a coneplate viscometer. Apparent viscosity in vivo was analyzed by comparing pressure-flow relationships for blood and a reference solution. Polycythemia decreased blood flow by 35% in the non-working muscle but less than 10% in the working muscle at comparable perfusion pressures. Blood viscosity in vitro increased by 35% at low shear rates. Apparent viscosity in vivo increased by 35% in the non-working muscle but less than 10% in the working muscle. The flow impairment induced by polycythemia was far more pronounced in the non-working skeletal muscle indicating a flow facilitation by the rhythmic muscle contractions. Erythrocyte flow in fact increased in the working muscle after induced polycythemia while decreased in the non-working muscle.