Hydroxyethylstarch 200 and 240 differently affect aortic distensibility but not viscosity and blood pressure upon acute isovolumic hemodilution.

Objectives: It has been shown that a hydroxyethylstarch solution significantly increases the aortic distensibility coefficient (ADC) as compared to other non-hydroxyethylstarch colloid solutions. In order to investigate whether the effect of hydroxyethylstarch on ADC is class-specific, we investigated the effect of two hydroxyethylstarch solutions (HES 200: Elohes and HES 240: Hesteril) on the ADC and compared them with two other colloid solutions: 5% albumin and fluid gelatin (Gelofusin) in a rabbit model of acute isovolumic hemodilution.

Methods: Twenty-eight male New Zealand white rabbits were anesthetized and randomly allocated to receive (n=7, each): albumin, hydroxyethylstarch-200, hydroxyethylstarch-240 and gelatin for acute isovolumic hemodilution by exchanging 13 ml.kg(-1) body weight of blood with an identical volume of the test solution. Blood viscosity, mean arterial pressure, aortic blood flow and heart rate were measured and ADC was calculated.

Results: All groups were comparable with respect to arterial pressure, heart rate and aortic blood flow velocity before and after isovolumic hemodilution. After hemodilution, ADC coefficient remained unchanged as compared with pre-hemodilution values with albumin, hydroxyethylstarch-240 and gelatin, whereas a sustained 3 fold increase was observed with hydroxyethylstarch-200.

Conclusion: These results demonstrate that minor physicochemical differences between two hydroxyethylstarch solutions result in measurable differences in ADC and suggest that the clinical effects of colloids should probably be analyzed for each type of colloid and not for classes of colloids (e.g. hydroxyethylstarch or fluid gelatins).