[Clinical and statistical considerations on the relation between hematocrit value and blood viscosity]

Blood viscosity at various speed gradients was determined in 186 patients, a range of 245 haematocrit readings varying between 12 and 72 being examined. Statistical analysis of the results revealed a direct proportionality relationship between the two parameters, with viscosity expressed in logarithms. The regression lines accentuate their slope as the speed gradient falls. When determined at high speed gradients, blood viscosity can quintuplicate its value by varying the haematocrit from 10 to 70, while it can increase fully ten times at low speed gradients with the same haematocrit reading variations. Using blood from the same subject, resuspended at different haematocrits, viscosity values were obtained along the lines of regression up to haematocrits of about 70; for higher readings, viscosity data lie above these lines to a greater extent the higher is the speed gradient. Emphasis is laid on the great importance of the haematocrit reading from the rheological viewpoint and the significant clinical deductions that can be made.