Intestinal hemodynamic effects of dextran-induced hyperviscosity in the cat.

A hyperviscous state with red cell aggregation and increased plasma viscosity was induced in cats by intravenous infusion of high molecular weight dextran. A segment of the small intestine was isolated with intact vascular and nervous supply and placed in a plethysmograph for determination of the intestinal tissue volume and capillary filtration coefficient. The intestinal blood flow was measured by a drop recorder unit. Measurements of intestinal blood flow, flow resistance and capillary filtration coefficient were performed during normotension and regional hypotension before and after infusion of high molecular weight dextran. After infusion of high molecular weight dextran, there was a twofold increase of blood viscosity and a threefold increase of plasma viscosity. Erythrocyte sedimentation rate exceeded 100 mm/h. Intestinal blood flow decreased by 35% during normotension and by 45% during regional hypotension. Intestinal flow resistance increased by 45% during normotension and by 65% during hypotension. The capillary filtration coefficient was not affected by the dextran infusion. It is concluded that the intestinal hemodynamic effects of high molecular weight dextran are mainly dependent of the increased plasma viscosity and that the number of perfused capillaries is not reduced by obstructing red cell aggregates.