The viscous characterization of hydroxyethyl starch (HES) plasma volume expanders in a non-Newtonian blood analog

Abstract

Although information pertaining to the viscous characterization of HES 130/0.4 Voluven^® and HES 260/0.45 Pentaspan^® is available, quantification is limited to 100% concentrations. We focus here on the quantification of their viscous behavior along with HES 130/0.4 Volulyte^® in a shear thinning non-Newtonian blood analog of aqueous xanthan gum and glycerol. Dynamic viscosities of multiple batches of HES fluids were measured through capillary viscometry. The viscous behavior of 100%, 25% and 12.5% concentrations were then measured through a closed flow loop across physiologically relevant flow rates. Measured viscosities were 2.57 millipascal second (mPa·s) 6.52 mPa·s and 2.48 mPa·s for HES 130/0.4 Voluven^®, HES 260/0.45 and HES 130/0.4 Volulyte^®, respectively. Pipe flow analysis found that all HES fluids displayed Newtonian behavior at 100% concentrations. 25% concentrations of both HES 130/0.4 fluids decreased analog viscosity 23%–29% at a flow rate of 1.0 ml/s and 16%–21% at a flow rate of 22.5 ml/s. At a flow rate of 22.5 ml/s, 25% and 12.5% concentrations of HES 260/0.45 resulted in analog viscosity changes of 3.9%–4.5%. Capillary viscosity reductions of approximately 7% and 14.5% in HES 130/0.4 Voluven^® and HES 260/0.45 suggest changes in molecular composition to batches previously measured. Maintenance of analog viscosity suggests that HES 260/0.45 would be suitable as a high viscosity plasma expander in extreme hemodilution through preservation of microcirculatory function and wall shear stress (WSS).