Shear-dependency of the predicted ideal hematocrit

Abstract

The ideal hematocrit is the hematocrit (Hct) value resulting in the highest value of Hct/viscosity (h/η) ratio and can thus be predicted from viscometric measurements with the use of equations such as Quemada's one which yield the determination of the bell-shaped curve of h/η as a function of Hct. In a series of recent papers we applied this approach to various populations, using viscometry at high shear rate (1000 s -1 ). However the shape of this curve has been reported to be dependent on the shear rate, resulting in a right-shift in this top value when Hct increase. We present here in 11 young recreative athletes the evolution of the predicted top of the h/η curve and optimal theoretical Hct and the discrepancy between theoretical and optimal values over the range of shear rates 1 to 6000 s -1 . Results show that the predicted optimal value of both h/η and Hct increases when shear rate increases and that the discrepancy between predicted «optimal» and actual values decreases and becomes almost asymptotic at very high shear (500 s -1 ). It is minimal at 2720 s -1 . The correlation between predicted «optimal» and actual values of both parameters describes the same evolution. Therefore, it is better for assessing h/η and its agreement with theoretical values, and for determining the theoretical ideal hematocrit, to measure blood viscosity at shear rates equal or superior to 500 s -1 .

Anterior inferior cerebellar artery occlusion accompanied by hemorheology-documented increased blood viscosity: a case report

“…13 Notably, two Asian studies have reported that blood viscosity at admission is higher in patients with stroke secondary to smallartery occlusion than in those with stroke associated with cardioembolism and largeartery atherosclerosis. 14,15 Hematocrit, the mechanical properties of erythrocytes, and plasma viscosity are the primary determinants of whole blood viscosity; 16,17 of these, hematocrit plays a key role. 18 Many previous studies have reported that hematocrit elevation increases stroke risk after adjusting for several variables.…”

“…Hematocrit, the mechanical properties of erythrocytes, and plasma viscosity are the primary determinants of whole blood viscosity; 16 , 17 of these, hematocrit plays a key role. 18 Many previous studies have reported that hematocrit elevation increases stroke risk after adjusting for several variables.…”