[Relation of blood viscosity, plasma viscosity and hematocrit]

The results from 398 consecutive measurements of blood viscosity, plasma viscosity and hematocrit were submitted to a statistical analysis. Hematocrit appeared to be the main determinant of blood viscosity, even though its influence was not so strong as illustrated in previous investigations. The correlation between blood viscosity and hematocrit appeared strictly connected with the red cell amount of the blood sample, being higher when the latter exceeded its physiological range; this correlation disappeared when red blood cell amount was strongly reduced, while the correlation between plasma viscosity and blood viscosity had an opposite behaviour. From these results we can conclude that correlations between hematocrit and plasma viscosity with blood viscosity have opposite trends and that a reciprocal interference is often present.