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STUDIES ON BLOOD VISCOSITY AT LOW SHEAR RATES
Annual rept. 1 Jan-31 Dec 1965
COLUMBIA UNIV NEW YORK COLL OF PHYSICIANS AND SURGEONS
Pagination or Media Count:
Blood viscosity was measured at low shear rates in a modified G.D.M. viscometer. At a shear rate of 0.01sec, the time required to reach the maximum torque reading was dependent on hematocrit and plasma protein concentration. When hematocrit and other plasma proteins were held constant, the rise time was inversely related to the fibrinogen concentration. The shear-rate dependence of blood viscosity was attributed to two factors, namely the interactions between cells and plasma protein which predominated at low hematocrits and the direct cell-cell interactions which became more important at high hematocrits. The addition of albumin to cell suspensions caused a proportionate increase in viscosity at all shear rates, whereas the addition of fibrinogen raised the viscosity preferentially at low shear rates. Suspensions of hardened erythrocytes showed much higher viscosity than normal cell suspensions at the same concentration. Furthermore, filters with 5 micron pores allowed the passage of normal cells but not the hardened cells. The early hemodynamic changes in endotoxin shock in dogs consisted primarily of a marked constriction of small hepatic veins and venules, causing reductions of venous return, cardiac output and arterial pressure. The hepatic venoconstriction was not dependent on sympathetic activity. Following a partial recovery, the cardiac output and arterial pressure decreased again at 40 minutes postendotoxin.
APPROVED FOR PUBLIC RELEASE