Dehydration in Frail, Older Residents in Long-Term Care Facilities

REVIEWS

Dehydration in Frail, Older Residents in Long-Term Care Facilities Fred M. Feinsod, MD, MPH, DSc, CMD, Steven A. Levenson, MD, CMD, Keith Rapp, MD, CMD, Mary Pat Rapp, MSN, GNP, Eloise Beechinor, RD, MPH, and Laurencia Liebmann, RD, MS

All human beings require adequate fluid and electrolyte balance to survive and to function normally. Water (also called “fluid”) and electrolyte imbalances often cause, exacerbate, or are exacerbated by, significant clinical illness.1 Adequate hydration must be considered carefully in determining the overall needs of frail, older individuals, because dehydration is the most frequent fluid and electrolyte disorder observed in long-term care (LTC) populations.2 Not infrequently, a subtle, complex picture challenges the clinical insights of the LTC staff and primary care provider. Hydration deficits range over a spectrum from minor or asymptomatic to profound and life threatening. While the term “dehydration” is often used to identify any degree of hydration deficit, it should be reserved for more advanced stages. Dehydration is the reduction of total body water due to limited intake of fluids and/or pathological fluid loss.3 The frail elderly are at high risk for dehydration,4 which may increase the severity of an illness as well as the risk of death.5 Indeed, dehydration renders frail older people residing in LTC facilities more susceptible to developing a number of morbidity-inducing conditions and infections (Table 1).6 – 8 To reduce the risk of such occurrences, LTC physicians and health care professionals must focus on fluid and electrolyte balance as much as on essential nutrients such as calories and vitamins. This article is the first in a series of three articles that are dedicated to hydration issues in LTC. It focuses on the important scientific and medical basis for managing fluid and

Division of Geriatric Medicine, University of Colorado Health Sciences Center, Denver, and Pinon Management, Lakewood, Colorado (F.M.F.), Genesis Elder Care, Baltimore, Maryland (S.A.L.); Geriatric Associates of America, PA, Baytown, Texas (K.R.); University of Texas–Houston Health Science Center, and Geriatric Associates of America, PA, Baytown, Texas (M.P.R.); US Department of Health and Human Services, Centers for Medicare and Medicaid Services, San Francisco, California (E.B.); and Seattle, WA (L.L.) Note: The opinions and assertions in this article are the private views of the authors and are not to be construed as official or reflecting the views of the Centers for Medicare and Medicaid Services. Address correspondence to Fred M. Feinsod, MD, CMD, PO Box 38219, Colorado Springs, CO 80937.

Copyright ©2004 American Medical Directors Association DOI: 10.1097/01.JAM.0000036697.72589.A8 S36 Feinsod et al.

Table 1. Common Conditions that are Associated with Inadequate Fluid Intake in Frail, Elderly Long-Term Care (LTC) Residents Orthostasis Confusion and disorientation Functional decline Recurrent falls Pressure sores Urinary tract infection Pneumonia Skin infection

electrolyte balance. The second article will focus on facility and medical director roles in managing fluid and electrolyte balance, and the third will discuss survey issues related to hydration. What is meant by adequate hydration? The body’s water content makes up two-thirds of its physical mass. For example, the body of a 70-kg adult contains approximately 47 liters of water. It has intracellular (within cells and organs) and extracellular (outside of cells) fluid compartments. Water moves freely between the two compartments, keeping the osmolality (the concentration of dissolved substances) equal.9 Although many physiological functions are affected by the aging process, intracellular hydration is not altered in healthy aging.10 The extracellular fluid compartment includes the interstitial (in between tissues and within body cavities) compartment and the intravascular (within the bloodstream) compartments.11 Extracellular fluid volume is about 20% of body weight, that is, about 14 liters in a 70-kg adult. Blood proteins and cellular elements are relatively confined to the intravascular space. In contrast, electrolytes, such as salt (sodium chloride, NaCl), move freely between the vascular compartment and the larger interstitial compartment (body tissues and cavities). Sodium (Na⫹) is the major extracellular solute (dissolved substance), and potassium (K⫹) is the major intracellular solute. Since sodium is effectively restricted to the extracellular compartment, sodium balance primarily determines extracellular fluid volume. If salt (NaCl) is retained, as in JAMDA – March/April 2004

congestive heart failure, the extracellular fluid volume expands. The reverse is also true. Potassium is the major intracellular electrolyte, and therefore the total body potassium content is large, approximately 3500 mEq. The serum or extracellular potassium usually reflects total body potassium. The kidneys excrete most of the normal potassium intake (approximately 100 mEq/day) to maintain potassium balance. The kidneys are the primary regulators of extracellular fluid volume and salt balance. Normally, large amounts of sodium are filtered through the kidneys each day. Of this, the kidney normally reabsorbs greater than 95% into the circulation. Many factors affect tubular sodium resorption, including aldosterone and peritubular protein. The renin-angiotensin system heavily influences adrenal aldosterone secretion. Aldosterone stimulates the rate of sodium absorption and increases the rate of potassium secretion in the distal nephron. Normally, the entire system (ie, sensors, kidneys, and other organs such as the adrenal gland) maintains a relatively constant extracellular fluid (ECF) volume despite wide variations in salt intake, as sodium excretion matches sodium intake. However, in certain illnesses (eg, heart failure, cirrhosis, nephrotic syndrome), sodium retention continues despite an expanded extracellular fluid volume, creating edematous states. Atrial natriuretic peptide (ANP) directly suppresses renin that in turn suppresses angiotensin II and aldosterone secretion.12 Thus, adequate hydration means that the body has enough water to maintain physiological cellular function and blood (intravascular) volume. However, the presence of enough water does not mean that it will be in the right locations or with the proper concentrations of electrolytes. As with all conditions or measurements (weight, skin condition, etc.), hydration status must be viewed in relation to overall body function and electrolyte balance. It is inconsistent with basic medical and geriatrics principles to treat or survey numbers (fluid calculations, renal function tests, etc.) out of such context. Hydration Risks in Frail, Older Persons Physiological changes resulting from the aging process render elderly individuals at risk for fluid and electrolyte imbalance (Table 2). For example, water homeostasis is altered in the elderly individual.13 With loss of protein in the elderly and the close physiological link between protein stores and total body water, the percentage of water comprising body mass changes from 65% in younger persons to 50% in the elderly. Therefore, water losses in the elderly create greater changes in body fluid osmolality.14,15 Furthermore, creatinine clearance falls sequentially during aging;16 however serum creatinine, which is not reflective of the glomerular filtration rate, usually remains in the normal range during healthy aging.13 Aged kidneys concentrate urine less efficiently,17 which may lead to excessive fluid and free water loss or retention. Periods of physiological stress such as urosepsis and pneumonia may accelerate fluid loss.13 In older individuals, adaptation to salt and ECF volume depletion is diminished.13 This is a consequence of altered renin release as well as elevated levels of ANP that suppress renin with subsequent decreases in angiotensin II and aldoSUPPLEMENT

Table 2. Physiological, Situational, Functional, and Comorbid Factors Increasing the Risk for Dehydration in Frail, Elderly Individuals Residing in Long-Term Care (LTC) Facilities Physiological13 Total body water decreases with age (reflects reduced protein stores) Aging kidneys concentrate/dilute less efficiently reducing fluid and electrolyte control (especially under stress) Blunted Renin release (predisposes to sodium wasting in the urine and exacerbates dehydration during emesis and loose stool) Reduced renal response to ADH (reduces renal ability to concentrate urine thereby contributing to hypovolemia and hypernatremia during stress) Elevated ANP levels (increased ANP levels during hypovolemic states suppress renin with subsequent decreases in angiotensin II and aldosterone, compromising ability to resolve hypovolemia and potentiates sodium wasting. Exacerbates dehydration during emesis and loose stool) Free water clearance is impaired during maximal water diuresis (potentiated by thiazide diuretics) Reduced thirst sensation (less ability to satisfy physiological fluid needs despite free access to water) Situational Fever and infection increase fluid needs and fluid loss Multiple medications may increase fluid loss (e.g. diuretics and cathartics), compromise renal function (e.g., NSAIDs), and/or reduce thirst sensation (e.g. phenothiazines, hypnotics) Increases in ambient temperature and environmental dryness increase fluid needs Functional Conscious reduction of fluid intake to reduce toileting needs and incontinence Limited ability to hold fluid-filled glass or cup Limited access to fluids in institutional setting Insufficient amounts of fluid provided during and between meals Insufficient amounts of fluid provided through PEG tubes Comorbidities Dementia compromises communication, ability to ask for fluids, ability to sequence steps in drinking (exacerbates reduced thirst observed in elderly) Neurological disease and conditions reduce swallowing efficiency and may cause intermittent aspiration Arthritis reduces ability to obtain fluids or manipulate glasses/cups Illness and frailty increases immobility and thereby reduces ability to obtain fluids COPD increases fluid loss through mouth breathing Aging skin predisposes to skin pathology (pressure sores, large skin tears, infection, weeping edema, burns) ADH ⫽ antidiuretic hormone; ANP ⫽ atrial natriuretic peptide; PEG ⫽ percutaneous endoscopic gastrostomy; COPD ⫽ chronic obstructive pulmonary disease; NSAID ⫽ nonsteroidal antiinflammatory drug.

sterone.18 Such salt-wasting can exaggerate clinical hypovolemia during periods of emesis and/or gastroenteritis.13 Also as a consequence of aging, the kidneys of elderly individuals Feinsod et al. S37

experience a blunted aldosterone response when presented with a potassium load as compared to kidneys of younger individuals.19 This may increase the risk for drug-induced hyperkalemia in the elderly.13 Aging kidneys can also lose their ability to dilute urine (or excrete free water in the urine), placing the frail elderly at risk for free water overload, causing hyponatremia. Such age-associated defects in urinary concentration ability are due to a failure of the aged kidney to respond to normal or elevated levels of circulating antidiuretic hormone (ADH).20,21 The propensity for hyponatremia increases risk for disorientation, changes in gait, recurrent falls, and ultimately seizures, coma, and death. The frail elderly often experience diminished thirst sensation as osmoreceptor sensitivity decreases with aging.22,23 Indeed, older individuals describe minimal thirst despite fluid deficit, and when provided with free access to water, lag in correcting plasma osmolalities as compared to younger individuals.19 Additionally, LTC residents may not request fluids for fear of incontinence or difficulty in toileting.24 Medication effects and mobility disorders may also place them at higher risk for dehydration.25 Some frail older people have trouble swallowing efficiently, thereby reducing their ability to drink adequate amounts of fluid each day. Swallowing is controlled by multiple cranial nerves and muscle groups, so ischemic or physiological injury affecting any of these areas may interfere with efficient swallowing. Common conditions such as neurological disease (Parkinson’s disease, recurrent strokes, ALS, etc), neurological decline (exacerbated by medication), pharyngeal defects (Zenker’s diverticulum), and cognitive decline may also affect swallowing in frail, elderly persons. Cognitive loss and medication-induced cognitive suppression can reduce the sensation, realization, and communication of thirst. Monitoring fluid intake and offering sufficient quantities of fluid are exceedingly important with cognitively impaired, LTC care residents. In addition to defective thirst and reduced urinary concentrating ability, which is not infrequently observed in older individuals, demented LTC residents may also experience defective central ADH release that manifests itself as a tendency to become hypertonic after overnight fluid fasting.26 Fluid Requirements for Frail, Older Residents Fluid requirements for frail, older individuals residing in LTC facilities should be calculated on an ongoing basis. Fluid (solute-free water) can be offered in the form of water, carbonated drinks, and juices. Daily fluid intake should approximate 1 mL per kilocalorie of nutrition consumed.27 Tubefeeding formulas contain about 750 cc of water per total liter of nutrient.4 Therefore, additional solute-free water is generally necessary to achieve daily hydration requirements. Since frail, elderly residents may require up to 40 or 45 kilocalories per kilogram per day, especially in the presence of pressure sores, weight loss, or postoperative conditions,28 daily fluid requirements may exceed 2 liters per day. Another approach to establishing daily fluid needs is to calculate 30 cc of fluid per kg per day29 with a minimum of 1500 cc per day.24 A third method is to calculate 100 cc of fluid per kg per day S38 Feinsod et al.

for the first 10 kg of actual body weight, then add 50 cc of fluid per kg per day for the second 10 kg of actual body weight, and finally 15 cc of fluid per kg per day for the remaining actual body weight.30 All of these approaches appear adequate for LTC populations, as long as they result in at least 1500 cc of fluid consumed per day31 through all routes (food, free fluid, etc.). It is not always possible to attain that goal, and it may be possible to maintain adequate fluid balance with less than 1500 cc daily. Some pathological conditions such as severe congestive heart failure (CHF) or renal failure necessitate fluid restriction. When fluid restriction is indicated or if maximum fluid intake is significantly below the general target, it may be useful to explain why a lower intake is considered adequate or is the best that can be attained in the context of that individual’s overall condition. Physician discussion and documentation are critical in this regard. Daily fluid intake should compensate for normal fluid losses in the urine and bowel as well as from the lungs and skin. However, under different clinical conditions, these losses can be accelerated and therefore require additional fluids.4 Fluids should also be adjusted according to environmental factors (hot weather, warm temperatures in the facility, high humidity, high altitude, and sun exposure), physiological changes (increased activity, increased minute ventilation), pharmacological changes (GI preps, diuretics), and pathology (loose stools, emesis, pressure sores, large skin tears, burns) (Table 2). Identifying Hydration Deficits in Frail, Elderly Individuals The practitioner and facility provider should determine whether the resident/patient has a hydration deficit or is at risk for developing one. Body systems affected by hydration deficits may differ from those affected by an illness (for example, pneumonia). Identifying individuals with hydration deficits can be exceedingly difficult in frail older adults, sometimes leading to unavoidable delays in diagnosis.32 Medications and acute illnesses and conditions may cause similar symptoms. Chronic infection may also reflect persistent hydration deficits in LTC populations.31 Combinations of clinical parameters such as a drop in blood pressure, orthostasis, dry mucous membranes, and generalized signs (Table 3) coupled with laboratory findings would strongly suggest more serious hydration deficits.33 Regardless of underlying causes, hydration deficits may present initially as nonspecific symptoms and signs such as lethargy, confusion, or agitation, or decline in function or cognition (Table 4). Therefore, delayed diagnosis of hydration deficits does not necessarily reflect poor performance by nursing facility staff but may be due to obscured clinical presentations that are not uncommon in the frail elderly. Because fluid and electrolyte imbalance is common and may not be readily apparent, physicians and nursing facility staff should suspect it under certain circumstances, such as a significant condition change, the new onset of a major symptom or problem or the worsening of an existing one, or an otherwise unexplained decline in function or cognition that is not otherwise clearly attributable to another underlying cause. JAMDA – March/April 2004

Table 3. Clinical Presentation, Indirect Effects, and Laboratory Indications of Dehydration in Frail, Elderly LTC Residents Contrasted with Clinical Presentation of the Normal Aging Process Clinical presentation of severe hydration deficits Longitudinal tongue furrows Upper body muscle weakness Exacerbates dysarthria Lethargy and drowsiness Inability to maintain posture (lateral slump sign) Sunken eyes Indirect signs/symptoms of fluid deficit and electrolyte imbalance Change in mental status or cognition Change in functional status Unsteady gait or inability to ambulate (recurrent falls) Foul smelling and/or concentrated urine Reduced appetite Fluid refusal Headaches Chronic infection Laboratory indicators of potential fluid deficit Elevated BUN/creatinine ratios Elevated serum sodium Elevated serum osmolality Elevated urine specific gravity Signs/symptoms of aging that may be confused with hydration deficit Reduced skin turgor Reduced capillary filling Orthostasis Dry, pruritic skin on extremities

Table 5. Levels of Severity for Dehydration States in Frail, Elderly Residents in LTC Facilities Level 1: Major, apparent, clinically significant Evident clinical parameters and/or causes present (delirium, lethargy, prostration) Level 2: Suspicious symptoms of uncertain clinical significance and cause Generalized symptoms present (change in function and/ or cognition) Level 3: Subtle, intermittent Fluctuating or non-specific symptoms that cannot be readily distinguished from usual fluctuations or abnormalities

presents with major and apparent signs and symptoms of dehydration, and the findings have unmistakable clinical significance. Level 2 dehydration occurs when signs and symptoms are suspicious for dehydration but are of uncertain clinical significance, and cause is undetermined. This occurs when general clinical signs and symptoms (such as change in function or cognition) are present, but specific clinical (dry mucous membranes, longitudinal tongue furrows, lateral slump sign) and laboratory findings may be less obvious. Level 3 dehydration is subtle and intermittent; its clinical presentation fluctuates. Defining the Nature of the Imbalance

Severity of Dehydration Once the diagnosis of dehydration is made, the severity of dehydration should be established. As in all individuals, condition changes in the elderly tend to occur on several levels (Table 5). Level 1 dehydration occurs when the resident

Table 4. Clinical Parameters Indicating Possible Hydration Deficits. LTC residents with signs or symptoms present in any two of the groups should raise the strong possibility of dehydration Low blood pressure (⬎25 mm Hg drop in systolic BP from usual BP systolic), or Rapid pulse (⬎100 beats per minute), or Orthostasis (Obtain BP, P in recumbent, then dangling, then standing positions. Wait two minutes before obtaining BP, P in each position. Positive findings include decrease of ⬎20 mm Hg systolic BP, decrease of ⬎10 mm Hg diastolic BP, and/or increase of pulse by 20 beats per minute) Plus Dry mucous membranes Longitudinal tongue furrows (Plus) Change in function (ADLs, usual activities), or Change in cognition, or Change in gait (Plus) Prostration, or Recurrent falls

SUPPLEMENT

All fluid and electrolyte imbalances tend to produce similar symptoms and signs, even though the causes may differ. Therefore, once a hydration problem has been identified, it is important to define the nature of the imbalance as best as possible as a basis for determining the proper treatments and future preventive efforts.32 For example, identify whether the problem is primarily one of fluid deficit, sodium deficit, both fluid and sodium deficit, excess water retention, or something else. Other tests such as serum and urine osmolality, and urine and serum sodium may help define a resident’s state of hydration. On the other hand, urine-specific gravity is poorly correlated with serum biochemical parameters of hydration.32 Generally, a high sodium suggests water deficit or water loss in excess of salt. Such a hypertonic hydration deficit is accompanied by serum sodium ⬎145 mmol/L and hyperosmolality (serum osmolality ⬎300 mmol/kg). Common causes of hypertonic dehydration are sources of significant fluid loss, such as diuretics (or combinations of diuretics and ACE inhibitors) and protracted diarrhea, or profound decreases in free water intake such as occur with pneumonia or because of lethargy caused by adverse drug reactions (ADRs). Dehydration with low serum sodium levels suggests salt deficit, salt loss in excess of water, or excess water retention. Diuretics may also cause hypotonic conditions. Giving too much free water to someone who already is experiencing hyponatremia may actually exacerbate the problem. Normal serum sodium and serum osmolality may be found in individuals with a proportionate loss of water and sodium.34 Feinsod et al. S39

Such isotonic fluid and electrolyte imbalance can occur during periods of prolonged vomiting or diarrhea as well as during a period of complete fasting. High BUN/creatinine ratios suggest low blood volume or inadequate forward circulation (eg, heart failure, shock). Identifying Causes It is important to identify the causes of an individual’s fluid and electrolyte imbalance so that they may be addressed, where possible. They may include causes of inadequate intake (eg, dysphagia, dementia, inability to access fluids, or physically drink from a cup), causes of excess loss (eg, diarrhea, fever, diuretics, cathartics, heat exhaustion, overexposure to sun and environment), and causes disrupting the body’s ability to balance and manage fluid and electrolytes (eg, renal failure, heart failure, poorly controlled diabetes, syndrome (of) inappropriate (secretion of) antidiuretic hormone (SIADH), diuretics, angiotensin-converting enzyme (ACE) inhibitors). Combinations of the above problems, such as continued use of diuretics while an individual has diarrhea or pneumonia, may further compromise hydration status. Managing Hydration Problems in Frail, Older Persons After defining the nature of any suspected or actual hydration problem, some intervention may be needed. Despite the use of the term “dehydration,” no single treatment such as simply providing more fluids suffices for all these situations. An inappropriate intervention may actually be harmful. The primary care provider must help sort out and explain these possibilities to staff, residents, families, and other concerned parties. Patients should be treated initially in accordance with their clinical presentation. If possible, waiting for laboratory test results can help guide more appropriate interventions. But laboratory tests may take 1 to 2 days to be processed and reported, especially in remote areas or on weekends. When someone is significantly symptomatic or at risk, treatment (rehydration) should be initiated while waiting for laboratory results. Underlying cause(s) should be identified and treated. For example, urinary tract infections, pneumonia, and causes of diarrhea should be identified and treated appropriately. The underlying fluid and electrolyte imbalance must be addressed. Fluid hygiene is important in the frail elderly and early identification and intervention is important to resolve problems before clinical sequellae become severe.35 Rehydration interventions depend upon the cause and the severity of the volume depletion and symptoms. Mild volume depletion can be treated by gradual oral rehydration or via existing feeding tube; moderate volume depletion should be treated by more rapid rehydration via oral, feeding tube, clysis, or possibly IV route (speed depends on severity and response); and severe volume depletion should be treated rapidly via the intravenous route. Documentation should indicate clearly if interventions are not warranted or are in conflict with the resident’s wishes, or if the causes or the consequences of the fluid and S40 Feinsod et al.

electrolyte imbalance are not treatable or should not be treated.36,37 The chart and care plan should reflect communication and coordination between the physician, staff, and resident (or their proxy decision maker) on this issue. Treatment goals should be established and carried out per the resident’s wishes. Monitoring Hydration At this stage, the practitioner and staff should be monitoring for (1) the course of any hydration deficit, (2) the onset of additional complications, (3) the impact of a selected treatment on the cause or symptoms, and (4) possible undesired effects of the treatments (such as heart failure or hypertension due to excessively rapid repletion). Frequent weight monitoring is a sensitive method to follow acute fluid shifts. Further treatment adjustment should be based on the information gathered by monitoring and testing. For moderate or severe hydration deficits, initial rapid rehydration may need to be slowed down, depending on the individual’s mental and overall functional status, lab results, and other factors. Once the immediate problem (eg, fluid volume deficit) is resolved, the risk of recurrent fluid loss or electrolyte imbalance may still be present. If so, the risk must be addressed. For example, diuretics or ACE inhibitors may need to be tapered or stopped as should laxatives when catharsis is brisk or frequent. Closer monitoring (orthostatic signs, input and output measurements, renal function testing) should continue until the risk has been reduced substantially. General clinical evaluation remains a mainstay in monitoring a resident’s hydration status.32 However, the general clinical picture combined with laboratory assessment provide an overall assessment of an elderly resident’s hydration status.38 Vital signs, general strength, function, and cognition should be monitored regularly in residents experiencing or at high risk for fluid and electrolyte imbalance. Laboratory parameters such as serum electrolytes, creatinine, BUN, osmolality, hemoglobin and hematocrit may also help. The second article in this series will review the roles of the medical director and facility staff in assessing hydration status and trying to prevent significant fluid and electrolyte imbalance. REFERENCES 1. Weinberg AD, Pals JK, Levesque PG, et al. Dehydration and death during febrile episodes in the nursing home. J Am Geriatr Soc 1994;42: 968 –971. 2. Lavizzo-Mourey R, Johnson J, Stolley P. Risk factors for dehydration among elderly nursing home residents. J Am Geriatr Soc 1988;36: 213–218. 3. Gross CR, Lindquist RD, Woolley AC, et al. Clinical indicators of dehydration severity in elderly patients. J Emerg Med 1991;10:267– 274. 4. Chernoff R. Nutrition. In: Geriatric Medicine, Jahnigen DW, Schrier RW, eds. Blackwell Science. Cambridge, MA 1996. 5. Kleiner SM. Water: An essential but overlooked nutrient. J Am Diet Assoc 1999;99:200 –206. 6. Chidester JC, Spangler AA. Fluid intake in the institutionalized elderly. J Am Diet Assoc 1997;97:23–30. JAMDA – March/April 2004

7. Mentes J, Buckwalter K. Getting back to basics: Maintaining hydration to prevent acute confusion in frail elderly. J Gerontol Nurs 1997;23:48–51. 8. Morley JE, Silver AJ. Nutritional issues in nursing home care. Ann Intern Med 1995;123:850 – 859. 9. Electronic Library of Medicine (MAXX–Maximum Access to Diagnosis and Therapy). Boston: Little Brown, 1999. 10. Ritz P. Body water spaces and cellular hydration during healthy aging. Ann NY Acad Sci 2000;904:474 – 483. 11. Heuther SE. The cellular environment: Fluids and electrolytes, acids and bases. In: McCance KL, Heuther SE, eds. Pathophysiology: The Biologic Basis for Disease in Adults and Children, 2nd ed. St. Louis: Mosby-Year Book, 1994, pp. 91–123. 12. Ohashi M, Fujio N, Nawata H, et al. High plasma concentrations of human atrial natriuretic polypeptide in aged men. J Clin Endocrinol Metab 1987;64:81– 85. 13. Beck LH. The aging kidney: Defending a delicate balance of fluid and electrolytes. Geriatrics 2000;55:26 –32. 14. Schoeller DA. Changes in total body water with age. Am J Clin Nutr 1989;50:1176 –1181. 15. Reiff TR. Water loss in aging and its clinical significance. Geriatrics 1987; 42:53–62. 16. Rowe JW, Andres R, Tobin JD, et al. The effect of age on creatinine clearance in men: A cross-sectional and longitudinal study. J Gerontol 1976;31:155–163. 17. Rowe J, Shock N, Defronzo RA. The influence of age on the renal response to water deprivation in man. Nephron 1976;17:270 –278. 18. Weidmann P, De Myttenaere-Bursztein S, Maxwell MH, et al. Effect of aging on plasma renin and aldosterone in normal man. Kidney Int 1975;8:325–333. 19. Mulkerrin, Epstein FH, Clark BA. Aldosterone responses to hyperkalemia in healthy elderly humans. J Am Soc Nephrol 1995;6:1459–1462. 20. Rolls B, Wood R, Rolls E, et al. Thirst following water deprivation in humans. Am J Physiol 1980;239:R476 –R482. 21. Phillips PA, Rolls BJ, Ledingham JG, et al. Reduced thirst after water deprivation in healthy elderly men. N Engl J Med 1984;311:753–759. 22. Leaf A. Dehydration in the elderly. N Engl J Med 311: 1984;791:2.

SUPPLEMENT

23. Rolls BJ, Philips PA. Aging and disturbances in thirst and fluid balance. Nutr Rev 1990;137–143. 24. Chernoff R. Meeting the nutritional needs of the elderly in the institutionalized setting. Nutr Rev 1994;52:132–136. 25. Silver AJ. Aging and risks for dehydration. Cleve Clinic J Med. 1990;57: 341–344. 26. Albert SG, Nakra BRS, Grossberg GT, et al. Vasopressin response to dehydration in Alzheimer’s disease. J Am Geriatr Soc 1989;37:843–847. 27. Food and Nutrition Board. Recommended Dietary Allowances, 10th ed. Washington, DC: National Academy Press, 1989. 28. Sullivan DH. Undernutrition in older adults. Ann Long-Term Care 2000;8:41– 46. 29. Grant A, DeHoog S. Nutritional Assessment and Support, 4th ed. Seattle, WA: Anne Grant/Susan DeHoog:1991, p. 239. 30. Skipper A, ed. Dietitian’s Handbook of Enteral and Parenteral Nutrition. Rockville, MD: Aspen Publishers, 1993. 31. Holben DH, Hassell JT, Williams JL, Helle B. Fluid intake compared with established standards and symptoms of dehydration among elderly residents of a long-term care facility. J Am Diet Assoc 1999;99:1447– 1450. 32. Weinberg AD, Minaker KL. Council on Scientific Affairs, American Medical Association. Dehydration. Evaluation and management in older adults. JAMA 1995;274:1552–1556. 33. Chernoff R. Thirst and fluid requirements. Nutr Rev 1994;52(supplement):S3-S5. 34. Minaker K. Principles of fluid/electrolyte balance and renal disorders in the elderly. In: Reichel W, ed. Care of the Elderly: Clinical Aspects of Aging, 4th ed. Baltimore: Williams and Wilkins, 1995, pp. 252–268. 35. Sheehy CM, Perry PA, Cromwell SL. Dehydration: Biological considerations, age-related changes, and risk factors in older adults. Biol Res Nurs 1999;1:30 –37. 36. Levenson SA, Feinsod FM. A protocol for managing ethical issues and medical decision-making. J Am Med Dir Assoc 2000a;1:77– 84. 37. Levenson SA, Feinsod FM. Using basic management techniques to improve end-of-life care. J Am Med Dir Assoc 2000b;1:182–186. 38. Stout NR, Kenny RA, Baylis PH. A review of water balance in ageing in health and disease. Gerontol 1999;45:61–66.

Feinsod et al. S41