Dehydration in Geriatrics

[OldSquidNewNurse]

MC Faes, MD, MSc; MG Spigt, PhD; MGM Olde Rikkert MD, PhD
Geriatrics Aging. 2007;10(9):590-596. ©2007 1453987 Ontario, Ltd.
Posted 12/26/2007


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.

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.
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 an important risk factor for the occurrence of dehydration, though it is largely unknown how the decline in TBW affects hydration of individual organs and tissues. The skin often seems to be much drier among older adults. This is only partly explained by the small decrease in water content of the stratum corneum of the skin.[14] Other histopathological changes must contribute substantially to the dry appearance of old age skin.

The severity of dehydration depends more on the relative than on the absolute loss of total, intracellular, and extracellular water.[4] The lower an individual's body weight and optimal amount of TBW, the sooner the loss of a relatively small amount of body water will cause symptoms and signs of dehydration. Reduced thirst and renal water conservation capacity are also risk factors, probably associated with aging per se.[5,7,8,15] If older adults are functioning independently they fulfill their daily needs for water easily with bouts associated with their meals and social drinks.[6,16] However, with increasing age a substantial number of older adults (up to 25% of persons age 85 and over) drinks less than 1 litre of fluids per day.[17] The limited capacity of homeostatic mechanisms to maintain fluid balance only becomes important when fluid balance is at risk.

Environmental and disease-related risk factors for dehydration have a very high prevalence among older adults. Lavizzo-Mourey identified the most important risk factors for dehydration in a large prospective study on a LTC population.[5] Being over 85 years old and female, having five or more chronic diseases, taking five or more kinds of medication, and being bedridden were significant risk factors in developing a moderate degree of dehydration. In the case of severe dehydration the odds ratios for these risk factors were very high. The weather (particularly hot weather), inability to feed oneself, poor mobility, and a low level of care were also significant but less prominent risk factors. Having Alzheimer's disease is an additional risk factor after having controlled for all these factors, because it is associated with increased dependence on others for sufficient water intake and physiological changes such as a low arginine vasopressine (AVP) level.[18] Individuals in an AVP-deficient state are prone to dehydration because of having a poor water concentrating capacity. These risk factors should be important triggers to alert physicians and nurses to the possibility of dehydration in older adult patients.

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%).[24-26] 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. 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.

Prevention and Treatment

It has been demonstrated that when older adults know that they should not trust thirst but should drink because it is healthy for them, water intake increases above the minimum intake of 1700 ml per day.[17] For calculating the minimum amount of fluid per day, a formula based on body weight is recommended: 1500 ml is the minimum water intake with 15ml fluid per kg to be added for the actual weight minus 20 kg. This formula can be used for older adults who are normal weight, underweight, or overweight.[36]

Geriatric nurses and caregivers play a crucial role in the prevention of dehydration, as it has been shown that verbal prompting to drink between meals was effective in improving fluid intake in more cognitively impaired residents of LTCs.[37] Less cognitively impaired residents increased their fluid intake if they were given the beverages they preferred. The increase in fluid consumption did not occur at the expense of reduced consumption of food or fluid during meals. Participants with higher BMI values showed larger increases in their fluid consumption, but underweight participants (BMI <20) also showed a significant increase in their fluid consumption. Although the fluid intake increased by these feeding interventions, the food and fluid intake of the majority of the participants was still inadequate (≤75%).[37] Long-term care residents, for example, eat far from 100% of their meals, whereas almost 80% of the total daily fluid comes from fluid intake associated with meals. Patients consuming less than 50% of their meals are at high risk for dehydration. Caregivers should be aware of and anticipate this hazard.[36]

Other dehydration prevention measures include having water easily reachable throughout the day, encouraging drinking water by repeating self-care actions like brushing teeth, allowing adequate time and supervision during meals, encouraging family members to participate in feeding, and registering fluid intake.[38] Taking medication with fluid should be promoted. One study showed that LTC residents receiving medication consume significantly more fluid during nonmeal feedings than residents without medication.[36] For community-dwelling older adults dehydration may be prevented by educating them and their families or caregivers on the importance of hydration and the risk factors for dehydration.[39]

Note: Edited due to length

[cougarnurse]

I recently read something about the thirst perception going on the fritz. Thanks for the article.