Reference change values for monitoring dehydration
- 24 March 2011
- journal article
- Published by Walter de Gruyter GmbH in cclm
- Vol. 49 (6), 1033-1037
- https://doi.org/10.1515/cclm.2011.170
Abstract
Background: Dehydration is a common medical problem requiring heuristic evaluation. Our aim was to develop a quantitative and graphical tool based on serial changes in either plasma osmolality (Posm), urine specific gravity (Usg), or body mass (Bm) to aid in determining the probability that a person has become dehydrated. A secondary purpose was to validate use of the tool by dehydrating a group of volunteers. Methods: Basic data were obtained from a recent study of biological variation in common hydration status markers. Four reference change values (RCV) were calculated for each variable (Posm, Usg, Bm) using four statistical probabilities (0.80, 0.90, 0.95, and 0.99). The probability derived from the Z-score for any given change can be calculated from: Z=change/[21/2(CVa 2+CVi 2)1/2]. This calculation was simplified to require one input (measured change) by plotting the RCV against probability to generate both an empirical equation and a dual quantitative-qualitative graphic. Results: Eleven volunteers were dehydrated by moderate levels (–2.1% to –3.5% Bm). Actual probabilities were obtained by substituting measured changes in Posm, Usg, and Bm for X in the exponential equation, Y=1–e –K·X, where each variable has a unique K constant. Median probabilities were 0.98 (Posm), 0.97 (Usg), and 0.97 (Bm), which aligned with ‘very likely’ to ‘virtually certain’ qualitative probability categories for dehydration. Conclusions: This investigation provides a simple quantitative and graphical tool that can aid in determining the probability that a person has become dehydrated when serial measures of Posm, Usg, or Bm are made.Keywords
This publication has 30 references indexed in Scilit:
- Biological variation and diagnostic accuracy of dehydration assessment markersThe American Journal of Clinical Nutrition, 2010
- Clinical assessment of dehydration in older people admitted to hospital: What are the strongest indicators?Archives of Gerontology and Geriatrics, 2008
- Understanding Clinical Dehydration and Its TreatmentJournal of the American Medical Directors Association, 2008
- Dehydration Despite Drinking: Beyond the BUN/Creatinine RatioJournal of the American Medical Directors Association, 2004
- Is This Patient Hypovolemic?JAMA, 1999
- Language Guiding Therapy: The Case of Dehydration versus Volume DepletionAnnals of Internal Medicine, 1997
- Dehydration. Evaluation and management in older adults. Council on Scientific Affairs, American Medical AssociationJama-Journal Of The American Medical Association, 1995
- Serum OsmolalityNew England Journal of Medicine, 1984
- The Hypertonic StateNew England Journal of Medicine, 1977
- Comparison of Methods for Calculating Serum Osmolality from Chemical Concentrations, and the Prognostic Value of Such CalculationsClinical Chemistry, 1975