Inter-species hemorheologic differences in arterial and venous blood

Background: Hemorheologic factors such as red blood cell (RBC) aggregation and deformability differ according to species. In many comparative hemorheologic studies, only venous blood samples have been used for measurements. There is little published information comparing arterial and venous blood differences between species. We compared hemorheologic factors in arterial and venous blood in rats, dogs and humans. Methods: Nineteen dogs and 12 rats were used. Human blood was obtained from 12 healthy volunteers. Blood gas analysis, hematocrit and elongation index which represents RBC deformability were measured in arterial and venous blood samples. The critical shear stress and aggregation index, both of which represent RBC aggregation, were also measured in arterial and venous blood. Results: There were no arterial or venous differences in hematocrit, critical shear stress, or elongation index in dogs. In rats, RBC aggregation was not measurable. The hematocrit and elongation index of arterial blood were significantly lower than those of venous blood in rats. There were no arterial or venous differences in hematocrit, aggregation index, or elongation index in humans. Conclusion: Arterial and venous hemorheologic factors differed depending on the species. Further standardization is necessary for the measurement of hemorheologic variables.