Dehydration in Geriatrics

MC Faes, MD, MSc; MG Spigt, PhD; MGM Olde Rikkert MD, PhD

Disclosures

Geriatrics and Aging. 2007;10(9):590-596. 

In This Article

Diagnosing Dehydration

Classical signs of dehydration such as loss of skin recoil time, increased thirst, and orthostatic hypotension have a low sensitivity in older adults (60-75%).[24,25,26] Specificity of abnormal skin recoil time at the forearm or subclavicular region, and a dry oral mucosa is a better indicator (80-90%) and may be used to rule in the diagnosis of hypertonic dehydration.[25] In the older adult, dehydration often causes atypical symptoms such as confusion, constipation, or less frequently fever or falls. Confusion, constipation, and falls are part of the very frequently occurring "geriatric giants," and therefore their specificity as a single parameter is far too low to be useful in diagnosing dehydration.

Three forms of dehydration can be distinguished on the basis of the plasma tonicity: hypertonic, isotonic, and hypotonic dehydration. Many studies on dehydration are limited to hypertonic dehydration. This diagnosis is easy to make by laboratory tests and unequivocal (e.g., serum sodium levels >150 mmol/L or serum osmolality >300 mosmol/L), but neglects the frequently occurring isotonic and hypotonic dehydration. Isotonic dehydration results from a balanced loss of water and electrolytes (e.g., by vomiting and diarrhea) and hypotonic dehydration results when loss of electrolytes exceeds water loss (e.g., by overuse of diuretics). The prevalence of isotonic and hypotonic dehydration among older adults has never been studied systematically, probably because of the difficulties in diagnosing them correctly. A proper diagnostic approach to dehydration in clinical practice should be sensitive and specific for all three forms of dehydration.

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