Influence of rheological parameters on the velocity of erythrocytes passing nailfold capillaries in humans

Abstract

One thousand two hundred and fifty-six subjects (apparently healthy subjects and patients with cardiovascular diseases) were registered in a prospective study including demographical and clinical data, rheological parameters (hematocrit, plasma viscosity, erythrocyte aggregation, erythrocyte deformability) as well as the erythrocyte velocity in human nailfold capillaries under resting and postischemic conditions.A multivariate regression analysis showed that under resting conditions there was no correlation between rheological parameters and erythrocyte velocity in capillaries. The blood flow regulation seemed to be so effective, that pathological changes of the blood fluidity showed no effect on the velocity of an erythrocyte passing the capillaries.During vessel paralysis in the early phase of the postischemic hyperemia following a stasis of three minutes in the vasculature distal to a pressure cuff at the upper arm a very clear correlation between the plasma viscosity and the maximum postischemic erythrocyte velocity in ipsilateral cutaneous capillaries could be observed (p < 0.0001) while none of the other rheological parameters seemed to play a role. In a subgroup of diabetic patients the erythrocyte aggregation (measured during stasis) also correlated with the erythrocyte velocity (p = 0.0175) besides the plasma viscosity.This shows that a correlation of rheological parameters with the capillary perfusion could only be found during vessel paralysis. In of diabetic patients besides the plasma viscosity also the erythrocyte aggregation correlated with the mean capillary erythrocyte velocity. Theses results are in agreement with the hypothesis from Barras that plasma viscosity determines the perfusion of microvessels. Under certain conditions e.g. diabetic disorder, also the erythrocyte aggregation plays a role.

Endothelial function and hemorheological parameters modulate coronary blood flow in patients without significant coronary artery disease

“…Our data provide support for the importance of blood viscosity as a determinant of flow, and our ROC analyses suggest that there is a "threshold" blood viscosity (in the range of MPV>8.7fL, hematocrit >42.6%) beyond which coronary microvascular perfusion is negatively affected. This concept is in partial agreement with recent findings by Jung et al reporting a correlation between blood viscosity correlates and maximum postischemic (but not resting) capillary erythrocyte velocity in a large cohort study (1256 healthy volunteers and patients) [19]. Beyond their effects on blood flow, hemorheological factors have also been suggested to be involved in the progression of atherosclerosis [20], although findings from our group recently reviewed in [14] appear to contrast this hypothesis.…”

Influence of red blood cell aggregation on perfusion of an artificial microvascular network

“…As the viscosity of the suspending medium is a major determinant of microvascular perfusion, these studies could not separate between the influence of RBC aggregation alone and viscosity of the suspending medium. 26,30,55 Carefully matching viscosity of both aggregating and non-suspending media in our experiments allowed us to draw the conclusion that RBC aggregation induced by dextran 70 per se did not affect AMVN perfusion.…”

“…matter of controversy whether increased RBC aggregation is beneficial and contributes to recovery from a disease, 20,21 whether it is a harmful process and thus perhaps a mediator of disease, [22][23][24] or an irrelevant parameter and only a marker of disease. 25,26 RBC aggregation affects hemorheology by increasing blood viscosity at low shear rates. 27 In tube flow, RBC aggregation occurs in the center axis of the tube, which leads to an increased cell-free layer near the wall.…”

“…Current experimental data are confounded by the fact that a change in RBC aggregation is accompanied by a concomitant change in plasma viscosity, which itself is a major determinant of capillary blood flow. 26,30 In this study we suspended normal human RBCs in two solutions of dextran with equivalent viscosities, but different capacity to cause RBC aggregation, namely, dextran 70 as aggregating medium and dextran 40 as nonaggregating medium. We measured the ability of RBCs suspended in these two different media to perfuse an AMVN.…”

Increased erythrocyte aggregation in patients with primary open angle glaucoma

“…9 It is known that, RBC aggregation affects the fluidity of blood in larger blood vessels, where the shear rate is low enough to allow RBC to aggregate. 10,38 The reports on RBC aggregation parameters in patients with glaucoma are very scarce. In patients with normal tension glaucoma, higher aggregation index values were demonstrated, when compared to those of the healthy controls.…”