Important Symptoms and Laboratory Measures
The initial assessment of fluid status of an older individual is often very difficult. It should answer not only whether there is dehydration but, if the patient is dehydrated, it should also describe the type of dehydration, its development in time, and its severity. Many studies have been performed in search of a single measure to determine dehydrated and not-dehydrated or euvolemic patients. However, decreased intraocular pressure,[27] absent axillary sweating,[28] increased plasma specific gravity, increased cerebrospinal fluid protein, or urinary colour have not fulfilled this need.[29,30] The diversity in dehydration episodes and the heterogeneity of the older adult population rules out a one-dimensional approach to diagnosing dehydration. It may be more valuable to select a set of clinical signs and symptoms and laboratory measures that have proved to be useful in the discriminative diagnosis of dehydration with and without salt depletion in older adults ( Table 2 ).[31] Gross et al. found that the seven signs that correlated well with dehydration severity (Kendall's tau ≥ 0.35, p<0.01), but were unrelated to patient age, (Kendall's tau ≤ 0.20, p>0.05) were the most valuable indicators of dehydration in older adults.[32] A problem with Gross's seven signs is that there remains some subjectivity in assessing them; therefore, a cardiovascular assessment of blood pressure and pulse rate should also be included. There is no scientific evidence for the widely used clinical guideline that loss of body water, i.e., water loss without concomitant loss of electrolytes, is more likely to result in confusion among older adults than combined the loss of salt and water. As suggested by the very high prevalence of acute confusional states, some older adult patients may become easily confused by every disturbance of fluid balance, whatever its nature.
Traditionally, serum creatinine, blood urea nitrogen (BUN), and the BUN/creatinine ratio are advocated as useful laboratory measurements in detecting dehydration and other pre-renal pathology.[33] Creatinine has proven to be the most sensitive measure.[34] In evaluating fluid balance to detect dehydration in older adults who are already known, for instance in long-term care, repeated measurements of a few laboratory variables are probably sufficient. Body weight proved to be most responsive to changes in hydration.[35]
Geriatrics and Aging. 2007;10(9):590-596. © 2007 1453987 Ontario, Ltd.
Cite this: Dehydration in Geriatrics - Medscape - Oct 01, 2007.
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