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Fluids & Electrolytes
OVERVIEW: Maintaining adequate fluid balance is an essential component of health at every stage of life. Age-related changes make older adults more vulnerable to shifts in water balance that can result in overhydration or, more frequently, dehydration. This article reviews age-related changes, risk factors, assessment measures, and nursing interventions for dehydration.
"I'm so jittery," says a 77-year-old man with type 2 diabetes to his daughter as he waits for a computed tomographic scan of his abdomen. It's noon, and having fasted at home since 10 pm last night in accordance with his physician's instructions, he appears apprehensive and uncomfortable. "My lips are so dry," he says. The man and his daughter have been in the waiting room for almost two hours. When he is finally called into the examination room, the X-ray technician struggles to find a vein for iv insertion because his veins are flattened.*
Dehydration-a fluid imbalance caused by too little fluid taken in or too much fluid lost or both-can occur quickly in all older adults, and the effects can be harmful. 1 And the problem is becoming more prevalent: hospitalizations for dehydration in older adults increased by 40% from 1990 to 2000. 2 In many cases, though, dehydration is avoidable. How often are older adults at risk because of unnecessary and lengthy fasts required before certain procedures or because of long waits in EDs where little attention is paid to fluid and food intake? How often are they at risk because nurses fail to assess their ability to pour from a bedside pitcher?
Fluid balance, the state in which fluid intake equals output, is essential to health, regardless of a person's age. In older adults, adequate fluid consumption has been associated with fewer falls, lower rates of constipation, and lower rates of laxative use, as well as better rehabilitation outcomes in orthopedic patients and reduced risk of bladder cancer in men. 3-5 Drinking five or more 8-oz. glasses of water (but not other liquids) per day has been associated with lower rates of fatal coronary heart disease in middle-age and older adults than drinking two or fewer glasses. 6 And in one study, drinking 16 oz. of room-temperature water before a meal resulted in significantly lower rates of postprandial orthostatic hypotension in older adults who had autonomic failure. 7
Potential consequences of dehydration include constipation, falls, medication toxicity, urinary-tract and respiratory infections, delirium, renal failure, seizure, electrolyte imbalance, hyperthermia, and longer time to wound healing (especially pressure ulcers). 8, 9 In older adults with many comorbidities, dehydration can precipitate emergency hospitalization and increase the risk of repeated hospitalizations. 2, 10 Most significantly, dehydration has been associated with increased mortality rates among hospitalized older adults. 11
Causes of dehydration include diarrhea, excessive sweating, blood loss, fluid accumulation, inadequate fluid intake, and fever. Illnesses that entail excessive urination, such as diabetes and hypercalcemia, may also put people at risk for dehydration.
Findings of a recent study by Bossingham and colleagues show that healthy, community-dwelling older adults have no differences from younger adults in "water consumption, total water intake, water output through urine, total water output, and net water balance." 12 In this comparison of older and younger adults using a controlled diet, the researchers found "markers of hydration status were within the range of clinical normalcy for all groups."
Morgan and colleagues found that "functionally limited, independently living" older adults had normal hydration after fasting 12 hours, as determined by normal values for the clinical markers of hydration, including urine specific gravity, serum osmolality, hematocrit, and serum sodium and hemoglobin levels-suggesting, the researchers said, "that dehydration is not solely a function of the aging process but may be more related to concomitant medical conditions or dependent living." 13
On the other hand, one recent study of dehydration in EDs found that 48% of older adults admitted had laboratory values indicative of dehydration; 80% of them lived in the community. 9
These studies and others suggest an important consideration: older adults, under normal conditions, maintain adequate hydration, but physical or emotional illness, surgery, trauma, or higher physiologic demands (as occurs in exercise) increase risk of dehydration. 14
In a recent study, I followed 35 nursing home residents for six months and found that 31% were dehydrated during that period. 15 Of those, 36% had had prior episodes of dehydration. Dehydration in nursing homes has been linked to inadequately trained nurses and insufficiently supervised certified nursing assistants. Specifically, Kayser-Jones and colleagues found that residents were not positioned appropriately for drinking (for example, some were lying on their sides in bed) and that they were rushed when given food and drink. 16 In addition, liquids were often inaccessible to residents who could drink without assistance, leading to extremely low daily intake of fluids.
With aging, it becomes more difficult for the body to maintain fluid balance. There are several reasons.
The thirst response, which is the body's primary mechanism of signaling the need for fluid, becomes blunted with age. This was apparent in a 2002 trial that compared men 51 to 60 years of age with those 20 to 28 years of age. During a strenuous 10-day hill-walking excursion, the older men had less thirst and became progressively dehydrated; younger participants had no dehydration. 17 An earlier study found that in older men, the serum markers of dehydration (serum osmolality and sodium level) took longer to return to normal after an episode of dehydration than they did in younger men. 18
From puberty to 39 years of age, total body fluid is about 60% of body weight in men and 52% in women; after age 60, total body fluid decreases to about 52% of body weight in men and 46% in women. 19 (Women have a higher percentage of body fat and less muscle mass than men do and therefore less total body fluid.) In addition, muscle mass is lost with age, increasing the proportion of fat cells, which contain less water than muscle cells do, resulting in a decrease in intracellular fluid volume.
Creatinine clearance, an indicator of the kidney's efficiency in filtering toxins from the blood, can decline with age. In a classic study, Lindeman and colleagues found that in "normal" patients, the "mean decrease in [creatinine clearance] was 0.75 mL/min/year" after age 40. 20 "Normal" patients were those who didn't have renal or urinary tract disease or use diuretics or anti-hypertensives. (However, the authors also noted that "one-third of all subjects followed had no absolute decrease in renal function.") This decline in function means that the kidneys are less able to concentrate urine, so water is lost that in a younger person wouldn't be.
Older age and black race have both been associated with an increased likelihood of dehydration. 21 Ciccone and colleagues found that upon admission to an ED, adults 85 years of age and older were three times more likely to have a diagnosis of dehydration than were adults 65 to 74 years of age. 22 Older black adults have higher prevalence rates of dehydration at the time of hospitalization than do older white adults. 11, 23
Medications that directly affect renal function and interfere with fluid balance include diuretics, laxatives, and angiotensin-converting enzyme inhibitors. Psychotropic medications, such as antipsychotics and anxiolytics, have anticholinergic effects that cause dryness of the mouth, constipation, or urinary retention-effects that can alter hydration status. Polypharmacy has also been shown to heighten risk: Lavizzo-Mourey and colleagues found a significant bivariate relationship between the use of more than four medications and severe dehydration in nursing home residents. 21
Level of physical dependency, one's ability to perform activities of daily living, has also been examined as a risk factor. Results from three studies, all carried out in nursing homes, are contradictory. In a 1988 study, those who required assistance with transfer and ambulation were found to be at higher risk for dehydration. 21 However, two more recent studies found that those with better physical function were at greater risk for dehydration. 8, 24 This somewhat counterintuitive finding may reflect environmental factors in nursing homes, where caregivers may be more attuned to highly dependent residents who cannot drink independently, leaving those who are able to care for themselves to do so. Such an approach may not work with residents who are physically functional but cognitively impaired. The study by Morgan and colleagues found that functionally limited but independent community-dwelling older adults had normal hydration status after a 12-hour fast, leading the researchers to conclude that dehydration may have greater associations to having many comorbid conditions or dependent living. 13
Cognitive impairment has been associated with dehydration in older adults.
Many people in early stages of dementia are undiagnosed, as they are still able to converse in a conventional manner and can usually accomplish self-care activities. The Hartford Geriatric Institute's series Try this includes a protocol entitled, "Recognition of dementia in hospitalized adults," for assessing older patients for cognitive impairment in acute care settings. 25 (For more information, see "Behaviors Associated with Dementia,"A New Look at the Old, July 2005.) Because people with dementia often forget to drink, their actual intake should be assessed; to do so, watch the patient eat, check to see if his water pitcher is empty or full, and ask him how he would get a drink of water if he were thirsty. Nursing interventions include prompts to drink at regular intervals to ensure an adequate intake.
Assessing ability to drink is difficult in a patient with fluctuating cognitive abilities. Because delirium is usually transitory, the nurse may have to provide fluids until it subsides. Because delirium is often a symptom of an underlying condition such as infection, adequate hydration is important. Furthermore, studies have shown that dehydration is often a cause of delirium. 26, 27
Dehydration occurs more frequently in older adults who are frail and in those with diabetes, cancer, cardiac disease, or acute infections (such as urinary tract infections, upper respiratory infections, pneumonia, gastroenteritis, or skin infections). 2, 11 In addition, having multiple comorbidities has been associated with dehydration. 9, 21
The use of urine color, as measured using a urine color chart, can be helpful in monitoring hydration status. 28, 29 The urine color chart has eight standardized colors, ranging from pale straw (number 1) to greenish brown (number 8). 28 Urine that is the color of pale straw usually indicates a normal hydration status; as urine darkens, poorer hydration may be indicated (after the effect of discoloration by food or medications has been ruled out). I have recommended that for older adults, a reading of less than 4 on the color chart is preferred. 15
The color chart is most effective when a person's average urine color is calculated over several days to establish an individual baseline color. If urine becomes darker, further assessment can be conducted and fluids adjusted to prevent dehydration. Certain medications (such as aspirin, warfarin, and multi-vitamins) and foods (such as fresh fruits and vegetables) can discolor urine; the best results have been obtained in older adults with adequate renal function. 15
The most reliable indicators of dehydration include elevated serum sodium, elevated serum osmolality, and the ratio of blood urea nitrogen-creatinine (see Table 2, above). Unfortunately, as is true of other standard tests, serum markers confirm a diagnosis of dehydration once it is too late to prevent it from occurring.
Dry oral mucosa, a furrowed tongue, decreased salivation, sunken eyes, decreased urine output, upper-body weakness, and a rapid pulse may indicate dehydration. 30 Although assessment of skin turgor on the sternum is a mainstay in the assessment of hydration level in younger adults, it's not a reliable indicator in older adults because of changes in skin elasticity that occur with age. A reduction in axillary sweat production is another unreliable indicator. 30, 31
Older adults should not consume large amounts of fluid at one time; although the definition of "large amounts" varies from person to person, some older adults may have diminished renal function, which may result in overhydration. 14 It's therefore essential that frail elderly patients with multiple comorbidities and several limitations in the ability to perform activities of daily living drink small amounts consistently throughout the day.
Calculating a fluid goal in hospitalized patients can help nurses to monitor fluid intake before difficulties arise. Results from a study comparing three well-known calculations showed the most effective standard to be the following: 100 mL/kg for the first 10 kg of weight, 50 mL/kg for the next 10 kg of weight, and 15 mL/kg for the remaining weight. 32 This option was considered "reasonable for patients whether they are of normal weight, underweight, or overweight."
Except those who may require fluid restrictions to prevent overhydration-those with severe congestive heart failure, renal failure, or certain severe mental disorders in which polydipsia is a feature-most older adults should have a fluid goal of at least 1,500 mL per day. Careful monitoring is required for symptoms that suggest congestive heart failure: new weight gain, pedal edema, neck vein distension, or shortness of breath. Finding the right amount an older adult should drink per day can be difficult, but it's important.
Simmons and colleagues found that fluid intake increased in nursing home residents who were given the beverages they requested. 33 Although water is often considered the best beverage, substitutions may include fruit juices, low-sodium soups, decaffeinated coffee and tea, and water-rich fruits (watermelon, berries, grapes, peaches) and vegetables (tomatoes, lettuce, summer squash). For those who request fluids not considered healthful, such as caffeinated coffee or carbonated drinks, occasional indulgence is appropriate. Drink temperature is also important, and preferences may vary.
In a recent study, I identified four categories of nursing home residents. 34
* Can drink. Functionally capable of accessing and consuming fluids, these residents may not understand the importance of drinking sufficient amounts, may not feel thirsty, or may forget to drink because of cognitive impairment. Those who can understand should receive education, a graduated cup, and their preferred beverages. Residents with cognitive impairment should receive frequent offers of drinks and invitations to social events that encourage drinking (see Tips for Nurses by Health Care Setting, page 43).
* Can't drink. Frailty or dysphagia makes these residents incapable of accessing or consuming fluids safely. Those who are physically dependent should receive assistance and a sports cup with a straw. Swallowing exercises, fluid-rich foods such as melons and pureed foods, oral care, and family education may help those with dysphagia.
* Won't drink. Although some residents can drink safely, they don't. They may fear incontinence or may never have consumed many fluids. Educate those with incontinence concerns, suggesting Kegel exercises; medication should be provided when necessary. For those who have never enjoyed drinking, encourage frequent small amounts of fluid and provide preferred beverages during activities.
* End of life. Hydration at the end of life should be based on advanced directives or the preferences of the patient or family. (See "Oral Complications at the End of Life,"A New Look at the Old, July 2004.)
D ehydration and volume depletion are terms often used synonymously. But they describe different syndromes with differing symptoms and management. Extracellular volume depletion is the result of a net loss of total-body sodium with a reduction in intravascular volume. Major causes of volume depletion include blood loss, diarrhea, and vomiting; people experience light-headedness and orthostatic hypotension. In nonemergency situations, such as diarrhea with a bacterial cause, fluids containing some sodium, such as ginger ale and clear broths, are best used for fluid replacement. Emergency fluid resuscitation in dehydration and volume depletion, which is beyond the scope of this article, differs significantly in terms of type of fluid used and the timing of the treatment. For more information, see "Language Guiding Therapy: The Case of Dehydration Versus Volume Depletion," by Marge and colleagues, in the November 1, 1997, issue of Annals of Internal Medicine.
Selective serotonin reuptake inhibiters (SSRIs) have become first-line treatment for depression in older adults. However, Dutch scientists found that people taking SSRIs had four times the risk of developing hyponatremia than those not taking the medications. The risk of developing hyponatremia was greatest in the first two weeks of treatment. 1 Therefore, it's essential to monitor serum sodium levels in older adults who have recently been prescribed SSRIs. Monitoring fluid intake is also important, because changes in fluid and sodium intake can intensify a developing hyponatremia. Changes in mental status, including lethargy or acute confusion, should be investigated immediately.
Movig KL, et al. Eur J Clin Pharmacol 2002;58(2):143-8.
A series of Webcasts designed to improve multidisciplinary care.
Further explore the topics presented in the series A New Look at the Old by going online; over the course of the series 15 free Webcasts will run, created through a collaboration of AJN, the Gerontological Society of America, and Trinity Healthforce Learning and sponsored in part through a grant from Atlantic Philanthropies. The Webcast "Staffing Matters" first aired in January, and a new program premiered in May on depression in older adults. For information on the schedule or to view an archive of previous Webcasts, go to http://www.nursingcenter.com/AJNolderadults. This Web site includes a forum for comments and questions about the Webcasts or articles in this series.
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4. Mukand JA, et al. The effects of dehydration on rehabilitation outcomes of elderly orthopedic patients. Arch Phys Med Rehabil 2003;84(1):58-61. [Context Link]
5. Michaud DS, et al. Fluid intake and the risk of bladder cancer in men. N Engl J Med 1999;340(18):1390-7. [Context Link]
6. Chan J, et al. Water, other fluids, and fatal coronary heart disease: the Adventist Health Study. Am J Epidemiol 2002;155(9):827-33. [Context Link]
7. Shannon JR, et al. Water drinking as a treatment for orthostatic syndromes. Am J Med 2002;112(5):355-60. [Context Link]
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Ensure that the hospitalized older adult has access to something to drink at all times. Offer fluids regularly, as the older adult may not experience thirst and therefore may not help himself. A water pitcher that is untouched at the end of the shift tells you much about the hydration habits of the older person in your care. Minimizing fasting times for surgery and diagnostic procedures is also important. In the ED, when appropriate, provide food and fluids to older adults who must wait longer than two hours.
Educate certified nursing assistants on the importance of consistent oral hydration and supervise their care of patients. 1 Provide preferred beverages during group activities or at teatime or nonalcoholic "happy hour," and use a beverage cart, which can create a social environment that encourages fluid intake. 2 For those with difficulty drinking, the use of positioning strategies, swallowing exercises, cuing, and good oral care should be tried before fluids are thickened for safe consumption. Family members can provide important information about hydration habits and fluid preferences and make offering fluids (the most successful strategy to increase consumption) a regular part of their visits. 2, 3, 4
Ask older adults about their daily fluid intake and discuss how much fluid to drink on a daily basis, pointing out the need for increased amounts of fluid during exercise, in hot weather, and during illness. Review medications that affect fluid balance and increase or decrease dosages as needed. Recommend to healthy older adults with adequate renal function that they monitor their urine color. 5 Remind older adults who have urinary incontinence that they shouldn't impose restrictions on their fluid intake to prevent incontinence episodes. Regardless of the type of incontinence, adequate intake of fluid, approximately 1,500 to 2,000 mL per day, is indicated to maintain hydration. 6
Assess the types and amounts of fluid the home care patient is consuming. Educate the patient on the best fluids to consume. Educate the family on the importance of hydration and the risk factors for dehydration and ask them to report any instance in which the patient is not eating or drinking as he normally does, as an older person can become dehydrated even after a day of reduced intake.
1. Kayser-Jones J, et al. Factors contributing to dehydration in nursing homes: inadequate staffing and lack of professional supervision. J Am Geriatr Soc 1999;47(10):1187-94. [Context Link]
2. Robinson SB, Rosher RB. Can a beverage cart help improve hydration?Geriatr Nurs 2002;23(4):208-11. [Context Link]
3. Mentes JC, Culp K. Reducing hydration-linked events in nursing home residents. Clin Nurs Res 2003;12(3):210-25. [Context Link]
4. Simmons SF, et al. An intervention to increase fluid intake in nursing home residents: prompting and preference compliance. J Am Geriatr Soc 2001;49(7):926-33. [Context Link]
5. Mentes JC, et al. Use of a urine color chart to monitor hydration status in nursing home residents. Biol Res Nurs 2006;7(3):197-203. [Context Link]
6. Burke MM, Laramie JA. Primary care of the older adult: a multidisciplinary approach. 2nd ed. St. Louis: Mosby; 2004. [Context Link]
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