Dehydration in older adults is a common and significant clinical problem. It is associated with more comorbidities, longer hospital stays, re-hospitalizations, and higher mortality rates (Fortes et al., 2015). Adverse health outcomes associated with dehydration in older patients include falls, fractures, heart disease, confusion, delirium, heat stress, constipation, kidney failure, pressure ulcers, poor wound healing, suboptimal rehabilitation outcomes, infections, seizures, drug toxicity, and reduced quality of life (Chan, Knutsen, Blix, Lee, & Fraser, 2002). Decreased thirst response, decreased ability to retain salt and fluid, numerous medications prescribed, and several concomitant diseases attribute to the higher prevalence of dehydration in this population (Luckey & Parsa, 2003).
Dehydration is one of the top 10 most frequent diagnoses responsible for the hospital admission of older adults in the United States (Sfera, Cummings, & Osorio, 2016). Conflicting epidemiological reports exist about the prevalence of dehydration in older patients, with numbers varying from 17% to 48%, depending on the method used to determine dehydration (Bennett, Thomas, & Riegel, 2004; Stookey, 2005). Prospective studies in long-term care facilities showed that residents were dehydrated in 50% of febrile episodes and 27% of the population in long-term care facilities referred to hospitals was admitted due to dehydration (Sfera et al., 2016). In the United Kingdom, 20% of older adults living in residential care facilities are dehydrated and 40% are dehydrated on hospital admission (El-Sharkawy et al., 2015; Siervo, Bunn, Prado, & Hooper, 2014). Simple and inexpensive oral rehydration is usually the mainstay of treatment. However, on hospitalization, many patients may be denied the correct course of treatment because of misdiagnosis. Therefore, early identification of dehydration is vital to reduce the number of complications (Fortes et al., 2015).
No single gold standard marker of hydration status exists (Armstrong, 2007). Clinical screening methods including signs and symptoms of dehydration, patient history, orthostatic blood pressure change, and urinary parameters are a simple and quick way to assess patients' hydration status, although they are often characterized by poor diagnostic performance (Shimizu et al., 2012).
Serum osmolality, electrolytes, and blood urea nitrogen to creatinine (BUN:Cr) ratio represent additional methods of identifying dehydration (Hooper et al., 2015). Serum osmolality measured directly is the reference standard for hydration status in older adults. Osmolality is central to physiological fluid control, acting as a trigger for thirst and renal fluid conservation (Hooper, Bunn, Jimoh, & Fairweather-Tait, 2014). Urine osmolality has limitations in the older population due to decreasing renal function with advanced age, and is therefore not ideal for determining the hydration status in this population (Fortes et al., 2015; Kyle et al., 2004). Saliva osmolality is a newer method of determining dehydration and can be a good early indicator, but is not yet routinely performed (Fortes et al., 2015).
Patients in institutional care are more often dehydrated (Leibovitz et al., 2007). Causes for this include inadequately trained nurses, insufficiently supervised certified nursing assistants, out-of-reach liquids, and inability of residents to drink enough liquids. In addition, liquids are often inaccessible to residents who can drink without assistance, leading to extremely low daily intake of fluids (Mentes, 2006). Dehydration is also closely linked to several pathologic conditions, including pyrexia, immobility, confusion, drowsiness, and depression (Bryant, 2007).
The aim of the current study was to assess the fluid balance status in older patients residing in institutional care or their home. A clinical research study was conducted to examine the values of different dehydration indicators in older adults. The study hypothesis was that dehydration is a common clinical problem in the older population and more commonly found in those living in institutional care.
Five hundred thirty-two older adults from lower Styria (Slovenia) were included in the study; of these, 266 resided in institutional care (i.e., Social Security institutions) and 266 resided in the home. They were all referred to the emergency department (ED) of the University Clinical Centre Maribor by their general physician on duty.
A quantitative prospective method of research was used for analyzing laboratory tested values of serum as markers of dehydration. Older patients who visited the ED in the University Clinical Centre of Maribor between June 24, 2014 and December 24, 2014, were included in the research.
Serum sodium, urea, creatinine, BUN:Cr ratio, and serum osmolality were used as markers of hydration status. The reference range for sodium was 135 to 145 mmol/L and the reference range for BUN was 7.8 to 21 mg/dL (Kirsztajn et al., 2014). Dehydration was defined as serum osmolality ≥300 mOsm/kg (Siervo et al., 2014). These tests were part of a routine blood chemistry panel in all ED-referred patients; the process of collection and amount of blood sample necessary for the study was therefore not an additional burden on participants.
All participants and/or their legal proxies were informed about the purpose, manner, and content of research, and were personally asked for cooperation. Legal proxies had written authorization and were most commonly patients' relatives or caretakers. Written consent was obtained before inclusion in the study. The study was performed in accordance with the ethical standards of the Declaration of Helsinki on biomedical research on human beings, Slovenian Code of Medical Ethics, and the Code of Ethics of Nurses and Medical Technicians of Slovenia. Patients' personal data were protected according to the law on personal data protection. The study was approved by the institutional ethics committee and issued a written authorization to conduct research.
Older patients with advanced heart failure and/or chronic kidney disease (CKD) were excluded from the study. Exclusion criterion was also incomplete laboratory data.
The classification of the New York Heart Association (NYHA) was used to assess heart failure. NYHA classification is a functional classification in which patients are placed in one of four categories based on their limitations during physical activity. Class I includes patients with no limitations of physical activity. Class II includes patients with slight limitations of physical activity, in whom ordinary physical activity results in fatigue, palpitation, or dyspnea. Class III includes patients with marked limitation of physical activity, who are asymptomatic at rest but experience fatigue, palpitation, or dyspnea with less than ordinary activity. Class IV includes patients who are symptomatic at rest and unable to perform any physical activity without discomfort (Raphael et al., 2007). Exclusion criteria were Classes III and IV for the current study.
Renal function was evaluated based on glomerular filtration rate (GFR), with the normal GFR value >90 mL/min/1.73 m2. To calculate the GFR, the CKD Epidemiology Collaboration formula was used (Kirsztajn et al., 2014). CKD was defined as abnormalities of kidney structure or function present for >3 months with implications for health (Kirsztajn et al., 2014). CKD Stage 1 included those with a normal GFR and evidence of pathologic urine findings or structural kidney abnormalities. CKD Stage 2 included those with GFR 60 to 89 mL/min/1.73 m2. CKD Stage 3A included those with GFR 45 to 59 mL/min/1.73 m2 and CKD Stage 3B included those with GFR 30 to 44 mL/min/1.73 m2 (Kirsztajn et al., 2014). Exclusion criteria for the current study were CKD Stages 4 (i.e., GFR 16 to 29 mL/ min/1.73 m2) and 5 (GFR <15 mL/min/1.73 m2). Patients on dialysis were therefore excluded. Patients with heart failure of NYHA Classes III and IV and GFR <30 mL/min/1.73 m2 are usually aware of appropriate hydration; therefore, the intake of fluids is usually determinate (commonly diminished or limited to 1 liter per day).
Statistical analysis was performed using SPSS version 20 for Windows. Various methods of descriptive statistics were used. Data were expressed in percentages, standard deviations, and medians, and presented as histograms. To test the distribution of variables, Kolmogorov– Smirnov, Mann-Whitney U, and Pearson's chi-square tests were used. To estimate the range of different tested values, 95% confidence interval was used (0.05 significance level); values were statistically significant if p < 0.05.
Five hundred thirty-two older adults participated in the study; 266 were from institutional care and 266 were from home care. Serum sodium, urea, creatinine, BUN:Cr ratio, and serum osmolality were used as markers of hydration status. Of 532 patients, 410 met inclusion criteria, of which 192 were from institutional care and 218 were from home care. Mean age of participants was 80 (SD = 7 years). Eighty patients were excluded due to being classified as CKD Stages 4 and 5, 28 were excluded because they were classified as NYHA Class III or IV, and 14 were excluded because of incomplete laboratory data. Detailed characteristics of participants are presented in Table 1 and Table 2.
Patients Included and Excluded from the Study (N = 532)
Patients in institutional care were more often classified as CKD Stages 4 and 5 than those living in home care (21.4% versus 8.6%, respectively). Patients in institutional care were also significantly older than those from home care (p < 0.0001). However, patients in institutional care and home care had similar levels of serum sodium (mean [SD] = 137 [5.0] mmol/L vs 137 [4.0] mmol/L, respectively; median in both groups was 138 mmol/L). Five patients (1.2%) were hypernatremic, with serum sodium >145 mmol/L. Patients in institutional care had higher average values of BUN than those in home care (mean [SD] = 23.8 [11.1] mg/dL vs 21.9 [9.3] mg/dL, respectively; median = 21.1 mg/dL vs 20 mg/dL, respectively). After performing Kolmogorov– Smirnov and Mann–Whitney U tests (U = 19025, z = −1.59, p = 0.112), no statistically significant differences were found between groups. In 219 patients (53.4%), BUN was >20 mg/dL. Patients in institutional care had average values of serum creatinine of 0.94 mg/dL (SD = 0.34 mg/dL) compared to 1.01 mg/dL (SD = 0.30 mg/dL) for those in home care (median = 0.91 mg/dL versus 0.96 mg/dL, respectively). After performing Kolmogorov–Smirnov and Mann–Whitney U tests, significant differences were found between groups (U = 18248.5, z = −2.24, p = 0.025). Histograms were used to determine the distribution of values between groups. BUN:Cr ratio in patients in institutional care was 26.4 mg/dL (SD = 10.7 mg/dL) versus 22.1 mg/dL (SD = 7.8 mg/dL) in patients in home care (median = 24.6 mg/dL versus 20.6 mg/dL, respectively). Patients in institutional care had higher values than patients in home care. The distribution was asymmetrical and pointed in the left side of the histogram. The difference between the two groups of patients was statistically significant (U = 15356.5, z = −4.65; p < 0.001). Average serum osmolality was 298.1 mOsm/kg (SD = 18.3 mOsm/kg) and the median was 299 mOsm/kg. The lowest recorded serum osmolality was 185 mOsm/kg, whereas the highest recorded serum osmolality was 502 mOsm/kg. Of 410 tested patients, 188 (45.9%) fulfilled criteria for dehydration. Dehydration was found in 51% of patients from institutional care (98 of 192 patients) and 41.3% from home care (90 of 218 patients). The difference between groups was statistically significant (α = 0.05, χ2 = 3.915, p = 0.024). Patients in institutional care had higher average serum osmolality than those in home care (mean [SD] = 300.1 [23.7] mOsm/kg vs 296.4 [11.6] mOsm/kg, respectively), with the median also being slightly higher in the former group (300 mOsm/kg vs 298 mOsm/kg). Histograms showed pointed distribution in both groups and after performing Kolmogorov– Smirnov and Mann–Whitney U tests, the difference between groups was statistically significant (U = 18115, z = −2.35, p = 0.009). Baseline statistics of different markers of dehydration in both groups are presented in Table 3.
Markers of Dehydration in Both Groups
The purpose of the current study was to assess the hydration status of older patients treated in the ED of the University Clinical Centre Maribor using basic laboratory data (i.e., serum sodium, BUN, creatinine, BUN:Cr ratio, and serum osmolality).
Of 410 patients who met inclusion criteria, 192 were from institutional care and 218 were from home care. Patients' average age was higher in those from institutional care and there were more female patients in institutional care and home care environments. The current results were expected, as female patients tend to live longer than their male counterparts and patients in institutional care facilities tend to be older than those in home care (Meslé, 2004; Nores, 1997).
The results show that dehydration is a common clinical problem in older adults and is comparable to results from other studies (Mentes, Wakefield, & Culp, 2006; Siervo et al., 2014). However, the prevalence of dehydration differed according to dehydration criteria. Only five patients had serum sodium levels >145 mmol/L, 53.4% of patients had BUN levels >20 mg/dL, and 62.7% of patients' BUN:Cr ratio was >20:1. Interestingly, statistically significantly higher levels of average serum creatinine were found in those residing in home care. This finding may be due to how older adults in institutional care tend to be less physically active and inadequately fed, and are therefore more prone to muscle mass wasting, which results in lower levels of serum creatinine (Leibovitz et al., 2007).
Discrepancies in different dehydration markers show why hydration status assessment in older adults is a diagnostic challenge. Serum sodium, BUN, and BUN:Cr ratio are frequently used as markers of dehydration, but their sensitivity is poor (Fortes et al., 2015). According to some studies, serum osmolality is currently the best method to determine hydration status in older patients (Hooper et al., 2014). Dehydration can be defined as serum osmolality ≥300 mOsm/kg (Hooper et al., 2015; Marra et al., 2016). Serum osmolality can be assessed as a state or single measure, does not require prior knowledge or measurements, and is central to physiologic fluid control (Armstrong, Maughan, Senay, & Shirreffs, 2013); however, it is influenced by dietary osmolar load, fluid volume, and exercise, and should be used cautiously (Armstrong et al., 2013). In the current study, 45.9% of patients had serum osmolality ≥300 mOsm/kg, further proving the high prevalence of dehydration in older adults.
Bennett et al. (2004) defined dehydration as BUN:Cr ratio >20:1 and, according to their findings, 48% of older patients included in the research fulfilled criteria for dehydration, which is similar to the current results. In the same study, only 26% of patients were found to be dehydrated based on clinical findings (e.g., sunken eyes, prolonged capillary refill time, dry mouth and tongue, low skin turgor, hypotension, tachycardia, darkened urine) (Bennett et al., 2004; Bryant, 2007). Wu, Wang, Yeh, Wang, and Yang (2011) found that 45% of older adults in institutional care drank less fluids on a daily basis than recommended and had clinical and/or laboratory signs of dehydration; similar results were found in other studies (Stookey, 2005; Stookey, Pieper, & Cohen, 2005). It must be said that the previously published data about dehydration in older adults show several problems in evaluation of hydration status. In fact, no gold standard for determining the hydration status in older adults in daily clinical practice is currently available (Armstrong, 2007). Clinical signs are not able to discriminate between dehydration and euhydration, and thus provide little help to physicians making an initial hydration assessment. With advancing age, the skin loses its elasticity, which affects skin turgor, and smoking and cold environmental temperatures cause peripheral vasoconstriction, which may result in false positives for capillary refill time. Anticholinergic medications and a reliance on mouth breathing in older adults can lead to dry oral mucosa (Sarhill, Walsh, Nelson, & Davis, 2001).
Although showing promise in healthy young cohorts, urine analysis is not a reliable method in identifying dehydration in older adults because of decreased renal function in older age. Many prescribed medications in older patients also have a potentially confounding effect on urine (Armstrong et al., 1994). Increased saliva osmolality (>94 mOsm/kg) could discriminate between dehydration and euhydration, demonstrating superior diagnostic accuracy than urinary parameters and currently used physical signs. The physiological mechanisms responsible for an increase in saliva osmolality during dehydration are unclear, but may be due to an increase in water absorption in the saliva gland and/or neural factors (Gurwitz & Rochon, 2002). Saliva is not simply an ultrafiltrate of plasma and its composition is regulated by autonomic nerves. Baseline sympathetic activity is increased in dehydration and stimulation of both alpha and beta adrenergic receptors lead to increased protein secretion in saliva, which could increase saliva osmolality independently of plasma osmolality, giving it a potential advantage in detecting impending dehydration. Further studies are needed to assess the potential advantages of detecting saliva osmolality in older adults (Ely et al., 2014).
The current findings suggest that dehydration (defined with serum osmolality) is a common clinical problem in older adults and significantly more commonly found in those residing in institutional care than those residing in home care (51% versus 41.3%, respectively). Dehydration can cause several complications and negatively impact short- and long-term prognosis. Older patients residing in institutional care often receive inadequate care, which can be seen in many forms, such as insufficient use of beneficial drugs, poor monitoring of chronic disease, and overuse of inappropriate or unnecessary drugs (Gurwitz et al., 2002); they are also more often prone to fluid imbalance (Leibovitz et al., 2007).
Compared to previous studies (Mentes, 2006; Weinberg, Pals, McGlinchey-Berroth, & Minaker, 1994), the current results show a similar percentage of dehydrated older adults in institutional care. The reason for this similarity is likely multifactorial. Inadequately trained caregivers and insufficiently supervised certified nursing assistants play an important role in the high prevalence of dehydration among older adults in institutional care. Old and infirm individuals are at increased risk of dehydration (Campbell, 2011). Some may intentionally restrict their daily intake of fluids due to difficulties in toileting, whereas others are not capable of drinking fluids by themselves (Dowd, Campbell, & Jones, 1996). Nurses play a crucial role in patient care. They are therefore in a prime position to perform early hydration assessment, implement appropriate intervention, and provide health promotion information (Bryant, 2007).
The research has some important limitations. It was geographically limited to Maribor and surrounding areas of lower Styria and does not necessarily correlate with findings elsewhere. Basic laboratory data were used because of their low costs, routine availability, and objectivity. Other methods of determining dehydration were therefore not included, although they would have complemented the standard laboratory data. Only patients admitted to the ED were included, which is an important limitation as it excluded those who were not in need of acute medical help. In addition, no data about drugs and/or comorbidities, except presence of heart failure and renal failure, were collected and analyzed.
The current study shows that dehydration in older adults is a common and important clinical problem. Proper hydration is an important parameter of health and should not be neglected. No gold standard to assess hydration status exists, which is supported by the current results. Future studies should focus on determining the best method of detecting dehydration because currently used methods have important limitations. A promising method for detecting early dehydration seems to be saliva osmolality and should be tested further. More attention should also be given to hydration of older adults, especially those living in institutional care. Nurses' role in patient care is crucial, and it is important that they are educated on how to properly hydrate older patients and prevent dehydration and its negative consequences.
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Patients Included and Excluded from the Study (N = 532)
|Patients who met inclusion criteria||410 (77.1)|
|Patients who did not meet inclusion criteria|
| CKD Stage 4 or 5||80 (15)|
| Heart failure (NYHA Class III or IV)||28 (5.3)|
| Incomplete laboratory data||14 (2.6)|
|Parameter||Mean (SD)||n (%)|
|Living in institutional care (n = 192)||82 (8)||135 (70.3)||57 (29.7)|
|Living at home (n = 218)||78 (6)||127 (58.3)||91 (41.7)|
|Total||80 (7)||262 (63.9)||148 (36.1)|
Markers of Dehydration in Both Groups
|Marker of Dehydration||Living in Institutional Care||Living at Home||p Value|
|Serum sodium (mmol/L)||137 (5)||137 (4)||—|
|BUN (mmol/L)||23.8 (11.1)||21.9 (9.3)||—|
|Creatinine (mg/dL)||0.94 (0.34)||1.01 (0.3)||0.025|
|BUN:Cr ratio||26.4 (10.7)||22.1 (7.8)||<0.001|
|Serum osmolality (mOsm/kg)||300.1 (23.7)||296.4 (11.6)||0.009|