Quantitative analysis of blood viscosity was performed on the basis of mathematical models of non-Newtonian fluid shear flow behavior (Casson, Ree-Eyring and Quemada). A total of 100 blood samples were drawn from clinically stable survivors of myocardial infarction, treated with aspirin or acenocoumarol and controls to these drugs. Whole blood and plasma viscosity were measured at a broad range of shear rates using a rotary-oscillating viscometer Contraves LS40. Numerical analysis of the experimental data was carried out by means of linear (for Casson) and non-linear regression for the remaining models. In the evaluation of the results, both the fit quality and physical interpretation of the models' parameters were considered. The Quemada model fitted most precisely with the experimental findings and, despite the controversies concerning the relationship between in vivo tissue perfusion and in vitro rheological measurements, seemed to be a valuable method enhancing investigation possibilities of cardiovascular patients. Our results suggest that aspirin does not affect blood rheological properties, while acenocoumarol may slightly alter red cell deformability and rouleaux formation.

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Blood viscosity is one of the most important factors determining the blood flow. In this report we describe changes in whole blood viscosity in a group of patients after stroke measured as a function of the shear rate (flow curve) and also blood visco-elastic properties measured using oscillatory methods (dynamical mechanical analysis). The principle of the latter method is based on the measurement of the amplitude and phase of the sample oscillations driven by controlled harmonic strain. All measurements were performed by means of a rotary-oscillatory rheometer Contraves LS-40.

Rheology – the study of the flow of matter and accompanying phenomena of real bodies deformation – in relation to blood – hemorheology. Blood viscosity – the main rheological parameter – has been studied in many research centers and among many different group of patients. The main disorders related to the hemorheological properties are: coronary insufficiency, vascular congestion, myocardial infarction, cerebral circulation disorder, Reynaud disease, ischemic limbs, diabetes, anemia, tumors. The following parameters are the main blood viscosity determinants: plasma viscosity, hematocrit, red cell deformability and erythrocytes aggregation. In hemorheological studies we used mathematical rheological models. The measurements of blood and plasma viscosity are performed by means of oscillating-rotary rheometers in order to determine the dependence of blood viscosity on the shear rate and the two components of the complex blood viscosity. Determination of blood cells aggregability and deformability is performed directly by means of aggregometers and appropiate filters and indirectly using rheological techniques with advanced mathematical models of blood viscoelasticity. Blood and plasma viscosity are subject to autoregulation mechanisms of the body. Recognition of those mechanisms may help in assessment of some diseases risk: ischemic stroke or myocardial infarction. In many cases rheological measurements may reveal the most recent phases of diseases and disorderses which enables early therapy with specimens improving the blood fluidity. For this reason rheological measurements should be applied in diagnostics and therapy. Mutual relations between the main factors determining the blood viscosity and their effect on blood flow are the main subject of current report.