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Effect of hydroxyethyl starch (HAES) on degree and kinetics of erythrocyte aggregation studied with dielectric spectroscopy method.

BACKGROUND
Colloidal fluids, e.g. hydroxyethyl starch (HAES), used as blood plasma substitutes during acute controlled normovolemic hemodilution may cause erythrocyte aggregation. The aim of the presented study was to assess the degree and rate of erythrocyte aggregation in the media containing different concentrations of HAES.


MATERIAL/METHODS
The experiments were carried out on heparinized venous blood and on erythrocyte suspension in 0.9% NaCl.


RESULTS
Under stationary conditions, an increase of blood and erythrocyte suspension relative electric permitivity (e), with an increase of HAES concentration in the sample, was observed after HAES supplementation. Sample flow through a measuring chamber resulted in decrease of the eL value (determined for 100 kHz). Stopping the flow led to non-linear increase of eL values in the function of time, where two components - characterized by rapid and slow variability, respectively, could be distinguished. The increase was characterized by t1 and t2 relaxation times, which can be related respectively to the process of erythrocyte rouleaux formation and to the formation of 3-D network aggregates.


CONCLUSIONS
1) The values of eL are differentiated by the degree of erythrocyte aggregation due to the presence of HAES, both in whole blood and in erythrocyte suspension in 0.9% NaCl solution, 2) The degree of erythrocyte disaggregation due to flow increases with the increase of flow intensity and correlates with decreasing eL value, 3) t1 and t2, which characterize the kinetics of erythrocyte aggregation, indicate a difference between aggregation processes taking place in whole blood and after hemodilution with HAES.