The non‐ionic surfactant Poloxamer 188 (RheothRx®) increases plasma and whole blood viscosity

Abstract

RheothRx®injection is an intravenous formulation of Poloxamer 188, a non‐ionic block copolymer surfactant which is actually used in clinical studies, e.g., during thrombolysis in acute myocardial infarction. We have analysed the influence of RheothRx®on plasma and whole blood viscosity of healthy individuals in vitro. For that purpose plasma was incubated with 0, 0.75, 3.75 and 18.75 mg/ml RheothRx®and whole blood with a constant hematocrit of 41.4% with 0, 0.4, 2 and 10 mg/ml RheothRx®at 37 ${}^\circ$ C. Viscosity was measured with a Couette viscometer at shear rates of 94, 11, 0.9 and 0.1 s $^{-1}$ as well as with a newly developed oscillating viscometer. In contrast to other studies, we found no favourable effect of RheothRx®on plasma and whole blood viscosity. At the highest RheothRx®concentration an increase in high and low shear viscosity was observed. Erythrocyte morphology remained unchanged. These data, although on normal blood in vitro, suggest that the positive effects of RheothRx®in vivo may not be caused by improved flow properties of blood, but could rely on other mechanisms.