S TUDIES on blood viscosity in vitro and in vivo are becoming more and more common. Experience and information continue to accumulate both in the physics of blood and in the correlation of blood viscosity to certain pathologic states.
It appears that an elevation of blood viscosity, either at low or at high rates of shear (or approximately at low or high flow velocities), may provide important information on the patient's state; information which, otherwise, can be obtained only by laborious tests or belatedly deduced from clinical symptoms.
The term "high viscosity syndrome" describes a condition of high blood viscosity. As an elevation of blood viscosity may be due to complex causes and as the elevation may or may not be easily apparent, depending on the method of testing, the term "rheologic syndrome" may be considered more appropriate by the purists.
This review is, by necessity, incomplete. It is not