Pharmacodynamics and organ storage of hydroxyethyl starch in acute hemodilution in pigs: influence of molecular weight and degree of substitution.

OBJECTIVE: To determine the differential influence of molecular weight and the degree of substitution of HES solutions on pharmacodynamics and pharmacokinetics including organ storage in a model of acute hemodilution in pigs. DESIGN: Prospective controlled randomized animal trial. INTERVENTIONS: After bleeding, 20 ml/kg, animals were substituted with 6% HES preparations (200/0.62, 200/0.5, and 100/0.5). MEASUREMENTS AND RESULTS: We did not observe any significant differences in the ability to sufficiently achieve plasma volume expansion and restoration of macrocirculation, nor maintenance of indicators of microcirculation between the groups. Urine production was significantly higher in HES-treated animals and highest in animals substituted with HES 100/0.5. Plasma clearance was measured under steady-state conditions with significantly reduced clearance for the HES 200/0.62 group compared with HES 100/0.5 and HES 200/0.5 (6.6 vs. 13.2 and 13.9 ml/min; P < or = 0.001), thus being dependent on the degree of substitution. Even after only 6 h, the amount of infused HES not detectable in either blood or urine was significantly higher in HES 200/0.62-treated animals (50.7% compared with HES 200/0.5 (28.8%), P = 0.020 and HES 100/0.5 (28.4%), P = 0.018), with its proportion rising over time. Finally, we could demonstrate considerable amounts of all HES solutions being stored in liver, kidney, lung, spleen and lymph nodes. CONCLUSIONS: All preparations analyzed sufficiently restored macro- and microcirculation; however, for all solutions relevant tissue storage of HES was observed after only 6 h.

Volume efficacy and reduced influence on measures of coagulation using hydroxyethyl starch 130/0.4 (6%) with an optimised in vivo molecular weight in orthopaedic surgery : a randomised, double-blind study.

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.