Renal water conservation and the volume kinetics of fluid‐induced diuresis: A retrospective analysis of two cohorts of elderly men

Autor: Robert G. Hahn
Jazyk: angličtina
Rok vydání: 2020
Předmět:
Zdroj: Clinical and Experimental Pharmacology & Physiology
ISSN: 1440-1681
0305-1870
Popis: Renal water conservation after an overnight fast mirrors the habitual intake of liquid. The hypothesis in the present study was that water conservation influences the diuretic response to infusion of two types of crystalloid fluid. Twenty‐three elderly male patients (mean age 72 years) underwent a total of 46 intravenous infusions of 1.0 or 1.5 L of either hypotonic non‐electrolyte fluid (glycine 1.5%) or isotonic electrolyte fluid (Ringer's acetate or 0.9% saline). Urine osmolality (used to indicate renal water conservation) and plasma creatinine were measured before the infusions started. A two‐volume model was fitted to repeated measurements of the blood haemoglobin concentration and the urinary excretion, using mixed‐effects modelling software. Urine osmolality was examined as a potential covariate to the fixed kinetic parameters. The results show that distribution and redistribution of infused fluid occurred twice as fast for the non‐electrolyte fluids as for the electrolyte‐containing fluids, while the urine flow showed less difference. For both types of fluid, high urine osmolality served as a statistically significant covariate to the rate constant describing urinary excretion. Simulations showed that a high pre‐infusion urine osmolality doubled the time required for the kidneys to excrete 50% of a 30‐minute infusion. High plasma creatinine independently prolonged the elimination of non‐electrolyte fluid. The use of 0.9% saline instead of Ringer's prolonged the excretion of electrolyte‐containing fluid. In conclusion, renal water conservation is a determinant of the diuretic response to crystalloid fluid, regardless of whether the fluid contains electrolytes, and it should be considered in fluid balance studies.
Studies of infusion fluids usually do not consider that the kidneys may be set to conserve or excrete the infused volume before fluid is administered. The present retrospective analysis of the kinetics of electrolyte‐free and electrolyte‐containing fluids showed that the excretion of both types of fluid were mathematically dependent on the urinary osmolality measured just before the study was initiated
Databáze: OpenAIRE
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