Strategies for Ensuring Good Hydration in The Elderly

Literature review by Wendy Wells NMD.

Dehydration is a frequent cause of illness and death in elderly people. It causes the hospitalization of many patients and its outcome may be fatal. Indeed, dehydration is often linked to infection, and if it is overlooked, the chance of death exceed 50%. Older individuals have been shown to have a higher risk of developing dehydration than younger adults. Modifications in water metabolism with aging and fluid imbalance in the frail elderly are the main factors to consider in the prevention of dehydration. Particularly, a decrease in the fat free mass, which is hydrated and contains 73% water, is observed in the elderly due to losses in muscular mass, total body water, and bone mass. Since water intake is mainly stimulated by thirst, and since the thirst sensation decreases with aging, risk factors for dehydration are those that lead to a loss of autonomy or a loss of cognitive function that limit the access to beverages. The prevention of dehydration must be multidisciplinary. Caregivers and health care professionals should be constantly aware of the risk factors and signs of dehydration in elderly patients. Strategies to maintain normal hydration should comprise practical approaches to induce the elderly to drink enough. This can be accomplished by frequent encouragement to drink, by offering a wide variety of beverages, by advising to drink often rather than large amounts, and by adaptation of the environment and medications as necessary. Nutritional Review. 2005 Jun;63(6 Pt 2):S22-9. Ferry M. Center Hospital University

Some sodium, potassium and water changes in the elderly and their treatment.

Creatinine clearance decreases with age by 1 ml/min/year after 40 years of age, although serum creatinine remains constant because of reduction of muscle mass. Reduction of water intake may occur in the elderly because of a reduced sensation of thirst; this is associated with a tendency to lose water with urine. The capacity to respond to sodium load is impaired in aged kidneys, thereby leading to extra cellular volume (ECV) expansion and hypertension. But there is also, in the elderly, a reduced capacity for retaining sodium (FENa is higher than in young subjects), making old subjects sensitive to salt depletion and ECV contraction. Hypernatraemia (Nas > 150 mmol/l) is not infrequent in the elderly (1%) and is usually due to water deficiency (old subjects should be forced to drink), and rarely to iatrogenic excess of sodium. It is the abrupt occurrence of severe hypernatraemia that causes neurological symptoms due to dehydration and brain shrinking, which may lead to cerebral haemorrhage and death. Hyponatraemia (Nas < 130 mmol/l) is frequent among the elderly (7-11%) and is mainly due to water overload, which is usually iatrogenic. Hypovolaemic hyponatraemia occurs when salt depletion causes ECV contraction > 10%, and is due to water retention in an attempt to normalize ECV. Hypervolaemic hyponatraemia is due to ADH hypersecretion because of a decrease in 'effective' circulating blood volume. 'Pseudohyponatraemia' may occur because of hyperlipidemia or hyperproteinaemia. It is the abrupt occurrence of severe hyponatremia that causes neurological symptoms (water intoxication), secondary to the oedomatous swelling of the brain within the skull. While rapidly occurring hyponatremia may be lethal, slowly occurring hyponatremia is usually asymptomatic. Rapid correction of hyponatremia may cause cerebral dehydration and 'osmotic demyelination syndrome' ('central pontine myelinosis'). Decrease (e.g. by diuretics) or increase (e.g. by ACE-inhibitors, non-steroidal anti-inflammatory drugs, beta-blockers) or serum potassium may occur in the elderly. Diuretics should be used with caution in elderly subjects to avoid salt depletion, hypotension and renal function impairment.Semin Nephrology 1996 Jul;16(4):277-88.

Abnormalities of water metabolism in the elderly.

Hypernatremia (high sodium in the blood that occurs with excessive fluid loss) is a frequent problem at the extremes of age, but particularly so in elderly individuals. Changes in the physiological responses to water deprivation with increasing age may be of particular interest in understanding the pathogenesis of hypernatremia in the elderly. When comparing healthy elderly men to younger controls, there are differences in the response to water deprivation. In older men, there are deficits in both the intensity and threshold of the thirst response. The ability to concentrate the urine also declines with age. There is both a decline in glomerular filtration rate and an increased incidence of renal disease with advancing age, which may contribute to impaired ability to conserve water. Because of a decrease in the percent total body water with age, equal volumes of fluid loss in young and old individuals may represent more severe dehydration in the elderly. Hyponatremia is seen in all age groups, but there are important differences in the elderly. When compared with postmenopausal women, menstruant (of childbearing age) women are over 25 times more likely to suffer permanent brain damage as a complication of hyponatremic encephalopathy. Furthermore, menstruant women suffer seizures or respiratory arrest at far higher levels of plasma sodium (110 to 130 mmol/L) than occurs in postmenopausal women (95 to 123 mmol/L). J Clinical Endocrinol Metabolism. 2001 Dec;86(12):5996-7.

Potassium depletion and salt sensitivity in essential hypertension.

To evaluate the actual role of potassium depletion on blood pressure, 11 hypertensive patients were placed on a 10-day isocaloric diet providing a daily potassium intake of either 18 or 80 mmol, with each subject serving as his or her own control; the intake of sodium (220 mmol/day) and other minerals was kept constant. On day 11 each patient was also subjected to central volume expansion by water immersion associated with either normal or low potassium intake. After a 10-day period of low potassium intake, systolic blood pressure increased (P < 0.02) by 5 mm Hg, whereas serum potassium decreased (P < 0.001) by 0.9 mmol/L; no significant changes in urinary sodium and a marked increase in urinary calcium excretion (P < 0.001) were found during the 10-day low potassium intake. PRA (P < 0.02) and plasma aldosterone (P < 0.04) concentrations also decreased during low potassium intake in hypertensive patients. Even though an identical natriuretic response was found during the water immersion experiments with either high or low potassium in the whole hypertensive group, the evaluation of hypertensive subjects in relation to salt sensitivity enabled us to disclose pronounced differences in the natriuretic and calciuretic response. In fact, although an impaired natriuretic ability and moderate calcium loss were particularly found during water immersion in those hypertensive subjects exhibiting a lower salt sensitivity index, a predominant calcium depletion appeared to be the most important consequence of potassium depletion in the hypertensive subjects with a higher salt sensitivity index. By confirming that potassium depletion may exacerbate essential hypertension, our data also suggest that not only sodium restriction, but also potassium and calcium supplementation, could be particularly advisable in salt-sensitive hypertensive patients. Clin Experimental Hypertens. 2005 Jan;27(1):95-112.

Potassium, magnesium, and electrolyte imbalance and complications in disease management.

Electrolyte balance is a critical issue in managing comorbid conditions in both diseased and elderly patients. Patients with hypertension and diabetes need careful regulation of their calcium and magnesium levels, whereas in patients with congestive heart failure, sodium and potassium levels also are critical. Herein we report the outcome of a round table discussion at which issues of renal magnesium clearance, magnesium and arrhythmic risk, ion balance in heart failure, diabetes, ischemic stress, oxidative stress in the cardiomyopathy of magnesium deficiency, roles of magnesium and potassium in bone metabolism and the aging population, and the role of electrolyte balance in hypertension have been discussed. In all these issues the maintaining homeostasis of potassium and magnesium is critical and the various therapies that impact on retaining these ions were discussed. Hallmark studies, i.e., Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial and Studies of Left Ventricular Dysfunction, have provided insight into treatment of patients with cardiovascular and progressive heart failure. These studies and the availability of potassium and magnesium sparing diuretics for use in these disorders provide relevant perspectives for treatment.

Electrolyte Balance

Hypo-natremia

Hyponatremia is the most common electrolyte imbalance. It is associated with kidney disease such as nephrotic syndrome and acute renal failure (ARF). Men and women with healthy kidneys have equal chances of experiencing electrolyte imbalance, and people with eating disorders such as anorexia and bulimia, which most often affect women, are at increased risk. Very young people and old people are affected more often than young adults.

Causes of Hyponatremia

Hyponatremia is caused by conditions such as water retention and renal failure that result in a low sodium level in the blood.

Pseudohyponatremia occurs when too much water is drawn into the blood; it is commonly seen in people with hypoglycemia (low blood sugar).

Psychogenic polydipsia occurs in people who compulsively drink more than four gallons of water a day.

Hypovolemic hyponatremia (with low blood volume due to fluid loss) occurs in dehydrated people who rehydrate (drink a lot of water) too quickly, in patients taking thiazide diuretics, and after severe vomiting or diarrhea.</