Minimum Fluid Requirements for Adults

Minimum Fluid Requirements for Adults

Given the data presented above, there are clearly many differences in fluid intake records and data collection methods, and it is therefore difficult to determine the actual water consumption profile of older adults. In addition, it is known that there are other ways to measure water balance, such as measuring urine production, that were not considered in these studies [31]. However, recognizing that such methods may not be appropriate for this population due to health problems commonly associated with aging (e.g., urinary incontinence and dementia) [32], it is true that evidence suggests that 24-hour urinary osmolality is a good indicator of appropriate hydration status in adults. According to Perrier et al. [33], 24-hour urinary osmolality ≤500 mOsm/kg can be a simple indicator of optimal hydration, representing a total daily fluid intake sufficient to compensate for daily losses, ensuring that urine production is sufficient to reduce the risk of urolithiasis and decline in renal function, and avoiding the high plasma concentrations of vasopressin involved in increased antidiuretic effort. In addition, there are other methods better suited to detect changes in hydration status. Various analytical tests, signs and symptoms have been considered that can help detect dehydration in older adults [34]. As there is no gold standard [35], it is necessary to clarify which indicators of dehydration should be included in this group, such as blood and urine tests to assess dehydration in the elderly. In terms of blood tests, dehydration can be detected by analyzing serum Na+, blood nitrogen/creatinine ratio (BUN/Cr), serum osmolarity and urine tests. In the elderly, hyponatremia is a common electrolyte disturbance; it is defined as a serum Na+ level of <135 mmol/L [36,37]. Although no single threshold for hypernatremia was defined for the elderly, Shah et al.

[38] concluded in a literature review that the range for hypernatremia may be between 140 and 150 mmol/L. With respect to BUN/CR; It is an indicator of dehydration when there is an increase in BUN, but Cr is normal (> 15:1). However, it should be noted that other authors have used different limitations. For example, Wu et al. [39] and Bennett et al. [40] used the value ≥ 20:1; Culp et al. [41] used ≥ 21:1 and Mentes [42] ≥ 25:1. The most commonly used blood test is serum osmolarity. As explained in the Introduction section, serum osmolarity is a key component of the balance of aquatic homeostasis.

There are many equations that can be used to calculate this. In fact, some studies have identified up to 35 different formulas [43,44]. The one considered best for the elderly is the one developed by Khajuria and Krahn [45], as it is able to predict serum osmolality measured in frail elderly people with and without diabetes, poor kidney function, dehydration and health disorders, and cognitive and functional status [43,46]. The most common limits for the elderly are 275 to ≤295 mmoL/L, while 295 to 300 mmol/L indicate impending dehydration and >300 mmoL/L are recognized as an indication for current dehydration [43,44,46]. Compared to people born female, those born male generally need more fluids to support their increased body mass, lower average body fat, and increased calorie intake each day. In addition, the threshold below which fluid intake is considered low also differs from study to study. In some studies, fluid intake is measured by the number of drinks drunk [24,25,30]. When these amounts are extrapolated to L/day, a low fluid intake of less than 1.5 L/day is suspected, values that have also been used in other studies [23,29]. Some studies have relied on individualized formulas of what a person should drink [22], while others are based on recommendations from international organizations [26,28]. For women, the total amount of water is about 11.5 cups per day and for men, about 15.5 cups.

However, these estimates include liquids consumed in both food and beverages, including water. You usually get about 20% of the water you need from the food you eat. Given this, women need about nine cups of fluid a day and men need about 13 cups to replenish the amount of water lost. At European level, EFSA [27] recommends 2.5 l/day and 2.0 l/day respectively for adult men and women. However, the European Society of Clinical Nutrition and Metabolism (ESPEN) [57] is the only body that distinguishes between adults and the elderly. Their recommendation is that older men drink at least 2.0 l/day and women 1.6 l/day. While there is some uncertainty about an appropriate guideline for fluid intake in older adults, this critical review clearly provides evidence that most international organizations do not take into account the physiology of aging in their recommendations, nor do they take into account the health problems that typically affect older adults. However, given all the evidence analyzed, it can be concluded that older adults should drink between 1.5 and 2.0 L/day [57,58,87,88].

In particular, it is recommended to follow the ESPEN [57] and EFSA [27] guidelines. ESPEN [57] is the only guideline that takes age into account and enjoys a consensus of 96% among experts. It is also based on EFSA`s recommendations [27]. This authority [27] takes into account all liquids consumed (from food to liquids). If it is known that about 20% of all liquids ingested come from food [94], this would lead EFSA [27] to recommend the same as the ESPEN guidelines [57], namely 1.6 l/day for women and 2.0 l/day for men. In this way, care is taken to avoid the negative effects of dehydration while ensuring that people with heart and kidney disease are equally safe with both recommendations. However, these recommendations do not preclude the possibility of further research to verify their effectiveness and safety with respect to the health of older adults. The main goal for the future should be to individualize treatments according to the physiology and state of health of the patient. In addition, it should be borne in mind that the pattern of fluid intake observed in Table 1 is different depending on the level of care of an older person and possibly due to environmental factors, staff care and the health status of each person. These research studies may be experimental in nature, comparing a control group to usual fluid intake and a second group to fluid intake suggested by the study designs, or longitudinal in nature, observing different fluid intakes and their effects over time on participants` health. In both cases, clinical variables such as urinary tract infections, pneumonia, pressure ulcers, hypotension, disorientation, confusion and electrolyte imbalances (hypernatremia, hyponatremia and hyperkalemia) should be monitored for results. In this way, it should also be possible to determine whether, in addition to the differentiation between adults and genders, the recommendations for older persons take into account the place of residence of that person.

In addition, in this type of study, it should also be possible to identify the effects of the initial state of health of the participants and the physiological aging of the human body. These recommendations apply to liquids from water, other beverages and food. About 20% of daily fluid intake usually comes from food and the rest from beverages. The water balance of older people can also be affected by other factors. According to a recent review by our research group [19] and using comprehensive geriatric risk factors [20], the sociodemographic factors most closely associated with dehydration were age and woman. In terms of clinical factors, infections, kidney and cardiovascular disease, and end-of-life situations have been found to be strongly linked. The most strongly associated functional factor was inability to cope with daily activities, while the main mental health factors were dementia and behavioural disorders. Finally, social factors associated with dehydration were institutionalization, skilled level of care requirements, and winter. In short, maintaining adequate fluid levels in older adults is a constant challenge [1]. However, a meta-analysis by De Vecchis et al. [89] showed that consumption of liberal fluid (>2.0 l/day) did not appear to have an adverse effect on adult patients with chronic heart failure (mean age 69.5 years, age range 60-75). Patients with limited fluid intake had similar rehospitalization and mortality rates to patients without a fluid intake limit.

The following diagram is from their original publication “The maintenance need for water in parenteral fluid therapy,” Pediatrics 1957. Holliday and Segar determined how many calories a patient burns as a weight factor. In summary, adequate hydration provides mental, physical and overall health benefits and ensures a better quality of life for older adults [84]. It can also mean significant cost savings for health systems. However, it should be noted that all of these health benefits of hydration can be affected by overhydration.

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