Dehydration in Geriatrics
Homeostasis of fluid balance is an important prerequisite for healthy aging. The high prevalence of disturbances of fluid balance among older adult patients has triggered clinical research on age- and disease-related changes in water homeostasis. Empirical findings on risk factors of dehydration and on diagnostic and therapeutic strategies are reviewed in this paper. No single measure has proved to be the gold standard in the diagnosis of dehydration. Diagnosing dehydration and monitoring fluid balance requires repeated measurements of weight, creatinine, and physical signs such as tongue hydration. Rehydration and prevention requires fluid on prescription (> 1.5 litre/day), and the route of fluid administration depends on the acuteness and severity of clinical signs.
Keywords: older adults, dehydration, fluid therapy, risk factors, diagnosis.
Introduction
There is substantial evidence to show that aging causes changes in body water composition, and that renal function and thirst perception on average decline among older adults.1-3 These three factors account for the prevalence of dehydration among the older adult population. In one American study, dehydration was diagnosed in 6.7% of hospitalized patients age 65 and over, and 1.4% had dehydration as the principal diagnosis.4 Prospective studies in long-term care facilities (LTCs) showed that residents were dehydrated in 50% of the febrile episodes and that 27% of the LTC resident population referred to hospitals was admitted due to dehydration.5,6 Dehydration also proved to be very common in community-dwelling older adults.7 Dehydration is not only a common but also a very serious condition in older adults. Mortality of patients with dehydration is high if not treated adequately and in some studies exceeds 50%.6,8 In terms of morbidity, several studies showed an association between high degrees of dehydration and poor mental function.9,10 Others found that dehydration was a significant risk factor for developing thrombo-embolic complications, infectious diseases, kidney stones, and obstipation.11,12 These findings demonstrate the importance of timely diagnosis and adequate treatment of dehydration to reduce its serious effects on older adult patients.
Unfortunately, an early diagnosis is often difficult because the classical signs of dehydration may be absent or misleading in an older patient. In this article, we review the most important age-related risk factors for dehydration because they may help to identify older adults most at risk for dehydration. Next, we summarize recent developments in the diagnosis, prevention, and treatment of dehydration in clinical practice.
Definitions
In 1995 the American Medical Association warned its members that there exists no absolute definition of dehydration, and that the signs and symptoms of dehydration may be vague, deceptive, or even absent in older adults.23 Dehydration can be defined as a clinically relevant decrease of an individual’s optimal Total Body Water (TBW) amount and may occur with or without loss of electrolytes.
Risk Factors
Hippocrates stated that older adults showed a general decline in total body water, and even declared that this loss of body water was the cause of all symptoms of aging. Recent cross-sectional and longitudinal studies in healthy older adult populations have unequivocally confirmed this classical dogma of a decrease in body hydration with increasing age, but only in the sense of a decrease in the absolute amount of TBW.13 However, it is difficult to accurately predict body hydration of individual older adults because of the large interindividual differences in body hydration. Nevertheless, the mean decrease of TBW with aging is