Does colloid-induced plasma hyperviscosity in haemodilution jeopardize perfusion and oxygenation of vital organs?
GROUND AND METHODS. The infusion of dextran solutions is associated with haemodilution and, under some conditions, with a slight increase in plasma viscosity. To clarify the compound effects of simultaneous haemodilution and plasma viscosity increases on macro- and microhaemodynamics, we investigated the changes in arterial perfusion (radiolabelled microspheres, 15 microns ΓΈ) and oxygenation (tissue Po2) of vital organs using an animal model of plasma hyperviscosity. In nine splenectomized beagles plasma viscosity was increased step by step from 1.06 (baseline) to 2.14, and 2.99 mPa.s by infusion of small amounts (4% of total blood volume) of an ultra-high-molecular-weight dextran (50% w/v, mw: 500,000). RESULTS. Despite the significant increase in plasma viscosity, cardiac output as well as specific organ blood flows in heart, brain, liver, and muscle rose steadily with each step of viscosity, while the haematocrit declined from 0.31 to 0.24 and 0.20, respectively. Medians of tissue P
