Introduction to hemorheology: theoretical aspects and hyperviscosity syndromes.

Whole blood behaves like a deformable colloidal particle suspension in a macromolecular medium. Pathological variations in the rheological properties of blood and the clinical symptoms they produce form the "hyperviscosity syndromes". The term "hyperviscosity" was originally used for characterising the plasma hyperviscosity observed during macroglobulinemia and it is only recently that the chapter covering hyperviscosity syndrome has been enlarged to describe the syndromes as a state which the increased blood viscosity and increase in flow resistance must be considered as the result of the rheological behaviour of blood taken as a whole (plasma and blood cells). The etiology of hyperviscosity syndromes can be: (a) an increase in total plasma protein levels, or the appearance of a monoclonal protein; (b) the increase in the number of blood cells; (c) the increase in the erythrocyte's internal viscosity; (d) the changes in the erythrocyte's viscoelastic properties; (e) the excessive aggregating tendency of the erythrocytes and perhaps that of the platelets.