Wirkungen kolloidaler Volumenersatz-mittel auf die Gerinnung : Unter besonderer Berücksichtigung der Hydroxyethylstärke

In this study the effects of in vitro hemodilution on coagulation are compared with the effects of in vivo hemodilution using thrombelastography (TEG). The in vivo hemodilution was performed by i. v. infusion of 1 000 ml 6 % solution of hydroxyethyl starch HES (2 formulations with HES 130/0.4, one with HES 200/0.5) in healthy volunteers during 30 min. The in vitro hemodilution was performed with blood samples taken before the infusion started. These samples were diluted with HES-solution until the hemoglobin measured at the end of the infusion was attained. The results reveal that the effects of in vitro hemodilution with HES on coagulation differ qualitatively and quantitatively from the effects of in vivo hemodilution. The in vivo TEG-parameters remained in the reference range of the method, however all in vitro TEG-parameters are out of the range of normal values. The isolated interpretation of the in vitro data shows an impairment of blood coagulation. The shortening of the reaction time as an indicator for the initiation of blood clotting points to activated coagulation by in vivo hemodilution with HES, whereas in vitro the prolongation of the reaction time indicates a retardation of clotting. Independent of the results of the in vitro investigations, the evaluation of the TEG- and other clotting parameters determined prior to the beginning of the infusion, at the end of the infusion and four hours after termination of the infusion of HES 130/0.4 and of HES 200/0.5 show alterations caused mainly by dilutional effects. These alterations cannot be interpreted as impairment of haemostasis. In the usual clinically used HES-preparation HES is dissolved in 0.9 % NaCl solutions. If NaCl solution is used as control in studies with HES, it has to be recognised that the additional volume expansion caused by HES did not occur by normal saline Therefore, the volume expansion following HES infusion lasts clearly longer than the volume expansion caused by normal saline. A mathematical compensation of the different effects, therefore is not correct.