Elimination kinetics of different hydroxyethyl starches and effects on blood fluidity

Abstract

In a single blind randomized cross-over study 6 volunteers each received infusions of 500 m1 of 6 different types of hydroxyethyl starch (HES) solutions. Between the test periods there was a regular wash-out phase of 3 months. The concentration and molecular weight distribution of the intravascular HES-molecules as well as the blood fluidity were determined before and up to 24 hours after the infusions. The C2/C6 substitution ratio and the molar substitution exert an essential influence on the elimination of the HES-molecules. An increase in the C2/C6 substitution ratio from 4.6 to 10.8 with unchanged molecular weight (MW) and molar substitution brings about an increase in the half-life of the elimination in the 13 -phase t1I2-13 from 10.4 to 19.5 hours. In case a high C2/C6 substitution ratio is combined with a high molar substitution (0.62 instead of 0.5), half-life rises up to 36.1 hours. Whereas the molecular weights of all medium-molecular HEStypes (MW 200,000) decrease, the medium molecular weight of the