Diuresis and Urinary Viscosity in Dehydrated Patients

Abstract

Dextran with a molecular weight of 40,000 was administered to patients in a postoperative and dehydrated state. In alternate cases, 2% of mannitol was added to the dextran solution. The infusion of dextran-40,000 alone was followed by a temporary but marked decrease in urine flow in 3 of 5 patients. The dextran infusion almost regularly caused a very high urinary dextran concentration and an extremely high viscosity of urine, while no consistent change in urinary osmolarity and osmolar clearance was observed. Infusion of dextran-40,000 with mannitol resulted in increased diuresis and osmolar clearance. Urinary viscosity and dextran concentration was much lower than when dextran alone was given. The present data indicate that dextran-40,000 does not act as an osmotic diuretic. In patients dehydrated or under the influence of increased antidiuretic hormone activity, infusion of dextran-40,000 alone may result in an extremely high urinary dextran concentration and urinary viscosity. It is suggested that this viscous urine may impair urine flow. Addition of a small amount of mannitol counteracted this undesirable effect of dextran-40,000 infusion in the dehydrated subjects.