Blood Rheology: Effect of Fibrinogen Deduced by Addition

Viscometric measurements near zero shear stress were made on human blood and on suspensions of red cells in saline solutions of dialysed and nondialysed fibrinogen at 37°C at an hematocrit of 40. The principal viscometric parameter studied was the yield shear stress. The higher the value of yield stress, the greater is the viscosity defined as the ratio of shear stress to shear rate, in the region near zero flow, and the greater is the variation of viscosity with shear rate. The yield stress, zero in suspensions containing no fibrinogen, was found to increase with the fibrinogen concentration. At a given concentration of clottable fibrinogen (up to 1.20 g/100 ml) the yield shear stress was substantially greater in suspensions of red cells in their original plasma than in saline solutions of fractionated fibrinogen. Dialysis of the fractionated fibrinogen had no significant effect on the viscosity characteristics. For a given concentration of fibrinogen added to saline solutions, a higher yield stress was produced in the presence of A+ cells than in the presence of O+cells.