Hemorheological aspects of the pathophysiology of cerebral ischemia.

In summary, these considerations show that the hemodynamic role of blood rheology in cerebrovascular insufficiency or stroke is still not clear. However, the arguments and data presented allow some conclusions that are of practical and theoretical value in the process leading to further clarification: Changes of blood viscosity as determined by coaxial viscometry cannot be used to predict quantitatively the changes of cerebral blood flow occurring. It is likely that characteristic rheological phenomena such as red cell aggregation and deformability, plasma viscosity, and protein composition are more important for the rheological aspects of microcirculatory supply function than is reflected by their contribution to macroscopic viscosity of the blood. Further studies of blood rheology in stroke should therefore certainly include quantification of those rheological properties that are more closely related to the in vivo flow behavior of blood and thus the magnitude and distribution of flow in the cerebral microcirculation.