Читать книгу Pathy's Principles and Practice of Geriatric Medicine - Группа авторов - Страница 409

Disorders of water imbalance, hyper‐ and hyponatremia, are common in a geriatric population. Among frail elderly patients in long‐term care, the incidence of these abnormalities may be as high as 18–63%. Elderly people, after fluid restriction, have diminished thirst and renal responsiveness to ADH but retain their ability to secrete ADH. Hypernatremia is prevalent in those with Alzheimer’s dementia, who have further compromises in both thirst and ADH secretion. Institutionalized frail elderly individuals are often dependent on caregivers for water intake, especially during times of inter‐current or febrile illness. Hyponatremia may be associated with an age‐related limitation of renal concentration ability. ADH may be inappropriately elevated due to medications or physiologically increased due to diminished effective arterial blood volume.

Hyponatremia may be associated with comorbidities of falls, bone fractures, and death from heart disease, although causality has not been proven. There are associations of chronic hyponatremia with underlying diseases (congestive heart failure or cirrhosis), and chronic hyponatremia is associated with dementia. There are also associations of acute changes in hyponatremia linked to delirium, gait disturbances, and falls. It would seem prudent to limit drugs that are associated with hyponatremia (commonly, thiazide diuretics and SSRIs) and avoid drugs that predispose individuals to orthostatic hypotension.²⁸

Correcting hypo‐ and hypernatremia should be guided by neurocognitive symptoms. In seriously symptomatic people or for hyponatremia ([Na⁺] <125 mEq/L) or hypernatremia ([Na⁺] >145 mEq/L), adjustments of serum over the ensuing 24 hours should be designed to increase the [Na⁺] by 6–8 mEq/L in hyponatremia (to avoid osmotic demyelination syndromes) or to decrease the [Na⁺] by approximately 10 mEq/L in hypernatremia (to avoid cerebral oedema). Vaptans are vasopressin antagonists that are shown to improve serum [Na⁺] in hyponatremia, allow discontinuation of fluid restriction, and have exhibited modest effects on quality of life testing. Further studies are necessary to provide guidance on the role of thirst and ADH responsiveness in cognitive disorders, what role dementia has in chronic hyponatremia, and the benefits of acute correction of hyponatremia in delirium states, parameters of gait, and neurocognitive function.