[Hemorrheology, microcirculation and oxygenation. Physiopathological and therapeutic aspects].

The oxygen transport chain in mammalians depends on adequate oxygen uptake, oxygen transport and oxygen delivery. In diseases with underlying perfusion disorders, for example chronic occlusive arterial disease, the oxygen uptake by the lungs is not altered and thus the oxygen saturation of arterial blood is normal. In this case however the reduced blood flow does impair the oxygen transport to tissue. Blood flow depends on several factors. In diseases with low flow states, the flow properties of blood play a major role because the viscosity of blood increases in the sense of a vicious circle at low flow rates. Since the hematocrit is one of the determining factors of blood viscosity, one possibility to improve microcirculatory blood flow is to decrease the hematocrit value. The problem is however to reach a hematocrit range whereby the viscosity of blood is markedly improved but without reduction in the oxygen transport capacity. Other methods to increase microcirculatory blood flow at constant hematocrit values are the improvement of red cell deformability and the reduction of erythrocyte aggregation. All these methods are nowadays used in a number of diseases, in which a "hyperviscosity syndrome" is present. In general, an improvement of hemorheological factors like blood and plasma viscosity, erythrocyte deformability and erythrocyte aggregation will improve microcirculatory flow and enhance oxygen supply to tissue.