Effects of Dextran-40 on Blood Viscosity in Experimental Macroglobulinaemia

Abstract

BLOOD viscosity may be raised in many diseases. This rise may compromise the perfusion and nutrition of organs throughout the body^1–3; therefore there is great interest in any agent capable of reducing blood viscosity. Dextran-40 has been thought to be unique in performing this function^3–7, but since its introduction as a plasma expander it has been the object of controversy because of conflicting reports about both its actual effect on viscosity and its mode of action^2,3,7–14. Solutions of this type of dextran, with an average molecular weight of 40,000 (also known as low molecular weight dextran⁸, low viscosity dextran^4,5 and ‘Rheomacrodex’⁶), were said to reduce blood viscosity by inhibiting or reversing the formation of erythrocyte (RBC) aggregates^1–7 the presence of which is thought to contribute to the elevated viscosity levels found in pathological states^1,2. The evaluation of dextran-40 is complicated, however, by the multiplicity of its effects, and particularly by its ability to expand the volume of plasma and reduce the haematocrit, alterations which in themselves lower blood viscosity^{1,2,3,4,6–8}. Indeed, many investigators have concluded that all the beneficial effects of dextran-40 can be ascribed to blood dilution^8,10–14, and evidence has appeared showing that this agent, like dextrans of higher molecular weight, will actually increase blood viscosity if the haematocrit is not permitted to fall^3,10,12,15. Nevertheless, some workers still feel that infusions of dextran-40 are of special value in the treatment of hyperviscous states, and that the beneficial effects of this agent are mediated, at least in part, through the dissolution of RBC aggregates⁷.