Hydroxyethyl starch impairs in vitro coagulation

BACKGROUND: Artificial colloids affect haemostasis. Particularly hydroxyethyl starch (HES) solutions may have detrimental effects on haemostatic mechanisms. METHODS: In a crossover study blood was withdrawn from ten volunteers. Ringer's acetate, 6% low molecular weight HES (MW 120,000/molar substitution ratio 0.7), 10% low molecular weight HES MW 200,000/0.5) and 6% high molecular weight HES (MW 400,000/0.7) or 4% albumin was added to venous blood samples to make either 20 vol.% or 50 vol.% concentrations of each of the solutions. Samples were analyzed by thrombelastography (TEG). RESULTS: All HES solutions at 20 vol.% concentration impaired haemostasis as demonstrated by decreased clot formation rate (alpha-angle and maximum amplitude (MA)). In contrast, Ringer's acetate and albumin improved coagulability at 20 vol.% concentrations. Coagulation time (r + K) was prolonged at 50 vol.% dilutions of all solutions. The median r + K was greater with HES 400 (P < 0.05) and HES 200 (N.S.) than with HES 120. CONCLUSION: We conclude that HES at 20 and 50 vol.% concentrations has an adverse effect on in vitro measures of coagulation. A 50% dilution with high molecular weight HES seems to impair coagulation more than low molecular weight HES. Ringer's acetate and albumin caused a hypercoagulable state at a concentration of 20 vol.%, but the higher concentration decreased coagulability.