Disturbed blood flow structuring as critical factor of hemorheological disorders in microcirculation.

Blood flow structuring is a phenomenon of co-ordinated self-organization of RBCs in the normal flow in microvessels which actually defines the blood rheological properties in their lumina. Under conditions of undisturbed macrocirculation and normal conductance of microvessels the blood flow structuring is a determining factor of the fluidity of the driven blood. The dynamic structuring of blood flow prevails in advancing of the driven RBCs with plasma in the shear field induced in microvessels. Term "blood flow structuring" was introduced to describe the self-organised behavior of the RBCs and plasma advancing in the arterio-venular direction in the rapidly perfused microvessels. It implies primarily the availability of parietal plasma layer and of RBCs driven in the axial core, the tank treading, deformation and orientation of the red cells, i.e., of their self-optimizing adaptive behavior which minimizes energy dissipation. Many local hemorheological disturbances in the microvessels are related to intensified RBC aggregation and to the subsequent local accumulation in the microvascular lumina, thus entailing disorders of the blood flow structuring. This, in turn, results in the decrease of flow velocity, to full blood stasis, despite a preserved local arterio-venous driving pressure gradient. Elevated blood plasma viscosity and considerably curtailed RBC deformability might also entail retardation and even stoppage of the RBC flow in microvessels. The transition of blood flow to blood stasis and again to blood flow represents a synergetic process in the critically underperfused microvascular networks. As to the WBCs and thrombocytes, they are not involved in the normal blood flow structuring in microvessels, but they can largely affect both the blood flow normal structuring and the flow velocity under various pathological conditions. The presented theoretical concept accounts for a wide variety of transition patterns from the normal to the pathological hemorheological phenomena in the microcirculation.