In Vitro Measurements of the Effects of Anticoagulants on the Flow Properties of Blood: The Relationship of these Effects to Red Cell Shrinkage

Citrate and oxalate increased the viscosity of blood as measured in a capillary viscosimeter. The elevated viscosity was accompanied by erytrhocyte shrinkage, manifest by the decreased hematocrit of blood anticoagulated with either of these agents. Plasma viscosity was not affected. EDTA, which does not alter cell size or shape, also failed to alter blood viscosity, while citrate no longer affected viscosity, if utilized in ACD solution, a milieu which prevents cell shrinkage. When erythrocytes were suspended in hypertonic NaCl, "blood" viscosity was also elevated in comparison to that of suspensions in lower concentrations of NaCl. The data indicate that blood viscosity will be elevated by anticoagulants which are permitted to shrink erythrocytes.