Regional ischemia and hyperviscosity

Abstract

The correlation between blood hyperviscosity and ischemia is easy to understand if we consider that every condition in which viscosity increases causes a decrease in blood flow and, viceversa, every condition in which viscosity decreases induces an improvement in blood supply to tissues. This finding has been demonstrated “in vivo” in all the diseases where a primary blood abnormality provoked a reduction of blood fluidity. On the contrary there is clear evidence that in other conditions charachterized by reduction of vessel bore, due to obstructions or stenoses, blood fluidity may decrease as a consequence of tissue ischemia. The administration of drugs capable of modifying vessel bore is followed by changes of blood viscosity (decrease after vasodilators and increase after vasoconstrictors). In patients where the vessel obstruction has been successfully removed with surgery, blood viscosity, previously increased, rapidly returned to normal level. These data confirm, in these pathophysiological conditions, the variability of blood fluidity and its dependence on primary vascular hemodynamic changes.