Fåhraeus Award Lecture: The dangerous red cell

Abstract

The human red cell may be dangerous because of individual abnormalities or collectively because of a high concentration. The normal range of red cell concentration is probably not optimal and between 1% and 4% of the population are at a significantly increased risk of cardiovascular complications because of a high red cell concentration, albeit within the normal range. There is evidence that it may act as both a primary and a secondary risk factor. A number of mechanisms may mediate this pathological effect, including a direct effect on blood viscosity and bulk blood flow, an effect on platelet aggregation and haemodynamic effects predisposing to thrombogenesis. The true optimal red cell concentration depends on larger number of variables than is usually accepted and may vary from individual to individual. The therapeutic value of normovolaemic haemodilution is discussed in this context.