Viscosity measurement of whole blood

Blood viscosity is a measurement of the thickness and stickiness of an individual’s blood. It is a direct measure of the ability of blood to flow through the blood vessels. It determines how much friction the blood causes against the vessels, how hard the heart has to work to pump the blood through the body, and how much oxygen is delivered to organs and tissues. Blood viscosity is correlated with all known risk factors for cardiovascular disease – elevated blood viscosity is a strong independent predictor of cardiovascular events.

There are different kinds of testing for blood viscosity. Serum or plasma viscosity measurements have an important role in the clinical management of patients prone to hyperviscosity syndrome. But this measurement does not account for haematocrit, blood cell deformability or factors increasing RBC (red blood cell) aggregation.

Whole blood measurement is more informative, because it is affected by the hematocrit value. Nevertheless the measurements are more complex as whole blood is a non-newtonian liquid and changes its viscosity with the applied shear stress. The blood viscosity rises and falls from one extreme to the other with every cardiac cycle – much like blood pressure

For that reason a meaningful blood viscosity test requires two numbers: systolic blood viscosity (high shear rate), which is affected by hematocrit; and plasma viscosity and diastolic viscosity (low shear rate), which is affected by several factors such as stickiness of platelets, immune complexes that increase the aggregation of RBCs, triglycerides, cholesterol, and many more.

For this report we proved whether the Lovis 2000 M/ME is applicable for this kind of application. Due to the possibility to perform an angle scan the instrument delivers viscosity values at different shear rates. Additionally, we tested the low-volume capillaries (100μL), which were specially designed for such kind of applications where sample volume plays an important rule.