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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.

The study aimed at initial determination and analysis of selected rheological parameters of blood in the group of diabetics and patients after myocardial infarction and compare the results to the symptoms observed in thermographical studies. The parameters studied were: whole blood viscosity, plasma viscosity, relative blood viscosity and hematocrit value. A group of 60 subjects took part in the study. The control group (20 persons) included the healthy subjects who had never suffered from any circulatory system disorders and who did not receive any drugs affecting the hemorheological parameters. The group of diabetics included 18 patients and the group after myocardial infarction included 20 patients. Blood viscosity measurements were performed by means of a rotary-oscillatory reometer Contraves LS 40 at the decreasing shear rate ranging from 100-0.01 s(-1) during a period of 5 minutes. For each blood sample the hematocrit value was measured using the standard method. The plasma viscosity was calculated from the linear regression of the shear rate dependence of the shear stress measured by means of the Contraves LS 40 reometer.

We investigated the influence of kind of fluids used for transfusion - crystalloids and colloids - on the rheological parameters of blood with a special focus on the range of low shear rates. The blood viscosity measurements were performed with the use of a rotary-oscillatory rheometer Contraves LS 40. The investigation includes the measurements of blood viscosity and a hematocrit value at three stages: before, just after and two hours after transfusion. On the basis of results obtained for a group of patients prepared for procedures in epidural anaesthesia we concluded that the dilution effect for colloids (HES and dextran) was maintained longer then for crystalloids (Ringer solution). Measurements of blood viscosity at the shear rate of 1 s(-1) showed that this viscosity had the smallest value in the group of patients with HES 200/0.5 as a transfusion fluid (p0.001).