The effects of hydroxyethyl starches of varying molecular weights on platelet function

We evaluated the effect of various hydroxyethyl starch (HES) solutions on platelet function. Blood was obtained before and after the IV infusion (10 mL/kg) of saline (n = 10), HES 70/0.5--0.55 (molecular weight in kD/degree of substitution; n = 10), HES 130/0.38--0.45 (n = 10), HES 200/0.6--0.66 (n = 10), or HES 450/0.7--0.8 (n = 10) in otherwise healthy patients scheduled for elective surgery. Collagen and epinephrine were used as agonists for assessment of platelet function analyzer closure times. Flow cytometry was used to assess agonist-induced expression of activated glycoprotein IIb/IIIa complex and P-selectin. Infusion of HES 450/0.7--0.8, HES 200/0.6--0.66, and HES 70/0.5--0.55 prolonged closure times and reduced glycoprotein IIb/IIIa expression, whereas saline and HES 130/0.38--0.45 had no significant effect on platelet variables. P selectin expression was not affected by any solution tested. In vitro experiments demonstrated a less inhibiting effect of HES 130/0.38--0.45 on closure times when compared with other HES solutions. This study shows that HES 450/0.7--0.8, HES 200/0.6--0.66, and HES 70/0.5--0.55 inhibit platelet function by reducing the availability of the functional receptor for fibrinogen on the platelet surface. Our data indicate that fluid resuscitation with HES 130/0.38--0.45 may reduce the risk of bleeding associated with synthetic colloids of higher molecular weight and degree of substitution.