Abstract
ObjectiveRenal conservation (retention) of fluid might affect the outcome of hospital care and can be indicated by increased urinary concentrations of metabolic waste products. We obtained a reference material for further studies by exploring the prevalence of fluid retention in a healthy population.MethodsSpot urine sampling was performed in 300 healthy hospital workers. A previously validated algorithm summarized the urine-specific gravity, osmolality, creatinine, and color to a fluid retention index (FRI), where 4.0 is the cut-off for fluid retention consistent with dehydration. In 50 of the volunteers, we also studied the relationships between FRI, plasma osmolality, and water-retaining hormones.ResultsThe cut-off for fluid retention (FRI ≥ 4.0) was reached by 38% of the population. No correlation was found between the FRI and the time of the day of urine sample collection, and the FRI was only marginally correlated with the time period spent without fluid intake. Volunteers with fluid retention were younger, generally men, and more often had albuminuria (88% vs. 34%, P < 0.001). Plasma osmolality and plasma sodium were somewhat higher in those with a high FRI (mean 294.8 vs. 293.4 mosmol/kg and 140.3 vs. 139.9 mmol/l). Plasma vasopressin was consistently below the limit of detection, and the plasma cortisol, aldosterone, and renin concentrations were similar in subjects with a high or low FRI. The very highest FRI values (≥ 5.0, N = 61) were always accompanied by albuminuria.ConclusionFluid retention consistent with moderate dehydration is common in healthy staff working in a Swedish hospital.
Highlights
Moderate dehydration is a difficult condition to detect in clinical medicine
No correlation was found between the Fluid Retention Index (FRI) and the time of the day of urine sample collection, and the FRI was only marginally correlated with the time period spent without fluid intake
Plasma vasopressin was consistently below the limit of detection, and the plasma cortisol, aldosterone, and renin concentrations were similar in subjects with a high or low FRI
Summary
One method developed in sports medicine is based on the concept that high urinary concentrations of metabolic waste products indicate dehydration. The loss of body water caused by physical activity causes the kidneys to conserve (retain) water, thereby raising the specific gravity of the urine, increasing the osmolality and the creatinine concentration, and causing darkening of the urine color [1,2,3]. This concentration process can be prevented by appropriate replacement of the body water lost during exercise. These observations suggest that water conservation could be a common trait in the general population
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
