Effects of Starch Volume Expanders on Blood Viscosity and Vascular Endothelial Markers

The intravenous fluid of choice for acute blood volume replacement remains controversial. We focus here on the two hydroxyethyl (HES) available in Canada: HES 130/0.40 (Voluven®) and HES 260/0.45 (Pentaspan®). Although information regarding their pharmacokinetic and risk/benefit profiles are available, how the infusion of these fluids could affect blood viscosity and vascular endothelial function in humans is largely unknown. Dynamic viscosity was measured at 21°C and 37°C through capillary viscometry. The HES solutions were driven through a closed flow loop at room temperature (21°C). Viscosity at 21°C was 7.62 centipoise (cP) for HES 260/0.45 and 2.73 cP for HES 130/0.40 decreasing to 4.23 cP for HES 260/0.45 and 1.72 cP for HES 130/0.40 at 37°C. Analysis of viscous behaviour through pipe flow found that HES 260/0.45 displayed marginal variations in viscosity suggesting Newtonian behaviour across our range of Re measured. HES 130/0.40 displayed an appreciable increase in viscosity at higher Re suggesting the presence of shear thickening behaviour. Human aortic endothelial cells (HAEC) and human microvascular endothelial cells (HMVEC) were exposed to the HES solutions and saline to identify chemical effects on vascular endothelium. Western blot quantification showed that E-selectin was the leukocyte adhesion receptor that was most strongly affected, and this was not dose dependent. Interestingly, HAEC and HMVEC had different responses to HES treatment, suggesting that different vascular tissues may have different outcomes to HES infusion. Protein expression in HMVEC decreased when exposed to both HES solutions.