Plenary Lecture

Abstract

Blood rheology is “overtly abnormal” in various haematological diseases classically designated as “hyperviscosity states”; these disorders are rare and can be easily diagnosed. Much more common are diseases with “covertly abnormal” blood rheology, in which the rheological abnormality is present as an epiphenomenon to a vascular disorder. In diseases such as retinal arterial occlusion and secondary RAYNAUD phenomenon (early manifestations of systemic sclerosis) there is evidence of “abnormal blood thixotropy” i.e. a pathological tendency of the blood to loose its fluidity when subjected to low shear stresses. This tendency is assumed to perpetuate a low flow state caused by other haemodynamic abnormalities. Isovolaemic haemodilution and plasmapheresis were employed with clinical success in retinal artery occlusion and secondary Raynaud phenomenon, respectively. The two forms of “antithixotropic” therapy were accompanied by clearly lowered blood thixotropy, clinical improvement and augmented blood flow.