RESUMO
BACKGROUND AND OBJECTIVE: Different types of hydroxyethyl starch (HES) affect blood coagulation differently. We studied the effects of HES 130/0.4 on coagulation in major orthopaedic surgery in relation to the pharmacological parameter in vivo molecular weight. METHODS: 52 patients were randomly allocated to either HES 130/0.4 (6%, mean molecular weight 130 kDa, molar substitution 0.4) or HES 200/0.5 (6%, control) in a double-blind fashion. Colloidal volume requirements for intra- and postoperative haemodynamic stabilisation were compared. Safety analyses of this pharmacological study included a comparison of coagulation factor tests, in vivo molecular weight, and HES plasma concentrations. RESULTS: The colloidal volumes given were similar at the end of surgery (1602 +/- 569 for HES 130/0.4 vs 1635 +/- 567mL for HES 200/0.5), 5h later (1958 +/- 467 vs 1962 +/- 398mL), and up to the first postoperative day (2035 +/- 446 vs 2000 +/- 424mL). HES in vivo molecular weight at the end of surgery was 88,707 +/- 13,938 versus 158,374 +/- 33,933Da (p < 0.001) and 5h later was 86,663 +/- 16,126 versus 136,299 +/- 26,208Da (p < 0.001). In parallel to the lower in vivo molecular weight, factor VIII and von Willebrand factor returned to almost normal in the HES 130/0.4 group up to 5h postoperatively, but not in the control group (p < 0.05). Residual HES plasma concentrations after 24h were low in the HES 130/0.4 group (1.0 mg/mL), but higher in the control group (2.6 mg/mL). CONCLUSION: HES 130/0.4 and HES 200/0.5 were found to be similar with regard to volume efficacy. Sensitive coagulation parameters returned more rapidly to normal in the HES 130/0.4 group. Lower in vivo molecular weight and more rapid excretion of HES 130/0.4 are the likely explanations for the smaller influence on coagulation in this group.