water changes are due to changes in pure water), that the total body water is either 50 or 60% of body weight, and that the insensible water losses are between 500 mL and 1500 mL over 24 hours, depending on the underlying illness, such as fever or diarrhoea. Therefore, it is mandatory to maintain close clinical and laboratory monitoring to allow for the large range of assumptions to remain within the desired correction range.
Conclusions
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.
Key points
The elderly are at risk of hypo‐ and hypernatremia and need to be evaluated for abnormalities in thirst or mentation, untoward effects of medications, or physiological effects on arterial blood volume.
Although hyponatremia is associated with comorbidities such as falls, bone fractures, and death, causality has not been proven.
Cautious correction of serum sodium should be guided by neurocognitive symptoms in hyponatremia by [Na+] 6–8 mEq/L/24 hours and hypernatremia [Na+] <10 mEq/L/24 hours.
References
1 1. Robinson AG and Verbalis, JG. Posterior pituitary. In: Melmed S, Polonsky KS, Reed Larsen P, Kronenberg HM, ed. Williams Textbook of Endocrinolgy. Elsevier; 2016:300–332.
2 2. Dineen R, Hannon MJ, Thompson, CJ. Hyponatremia and Hypernatremia. In: Jameson JL, et al, ed. Endocrinology: Adult and Peditric. 7 ed.: Saunders; 2016:1953–1964.
3 3. Morley JE. Dehydration, hypernatremia, and hyponatremia. Clin Geriatr Med. 2015; 31(3):389–399.
4 4. Woodward M, Gonski P, Grossmann M, Obeid J, Scholes R, Topliss DJ. Diagnosis and management of hyponatraemia in the older patient. Intern Med J. 2018; 48 Suppl 1:5–12.
5 5. Miller M. Hyponatremia and arginine vasopressin dysregulation: mechanisms, clinical consequences, and management. J Am Geriatr Soc. 2006; 54(2):345–353.
6 6. McKenna K, Thompson C. Osmoregulation in clinical disorders of thirst appreciation. Clin Endocrinol (Oxf). 1998; 49(2):139–152.
7 7. Begg DP. Disturbances of thirst and fluid balance associated with aging. Physiol Behav. 2017; 178:28–34.
8 8. Verbalis JG, Goldsmith SR, Greenberg A, et al. Diagnosis, evaluation, and treatment of hyponatremia: expert panel recommendations. Am J Med. 2013; 126(10 Suppl 1):S1–42.
9 9. Ellison DH, Berl T. Clinical practice. The syndrome of inappropriate antidiuresis. N Engl J Med. 2007; 356(20):2064–2072.
10 10. Adrogue HJ, Madias NE. Hypernatremia. N Engl J Med. 2000; 342(20):1493–1499.
11 11. Cowen LE, Hodak SP, Verbalis JG. Age‐associated abnormalities of water homeostasis. Endocrinol Metab Clin North Am. 2013; 42(2):349–370.
12 12. Luckey AE, Parsa CJ. Fluid and electrolytes in the aged. Arch Surg. 2003; 138(10):1055–1060.
13 13. Phillips PA, Rolls BJ, Ledingham JG, et al. Reduced thirst after water deprivation in healthy elderly men. N Engl J Med. 1984; 311(12):753–759.
14 14. Phillips PA, Johnston CI, Gray L. Disturbed fluid and electrolyte homoeostasis following dehydration in elderly people. Age Ageing. 1993; 22(1):S26–33.
15 15. Phillips PA, Bretherton M, Risvanis J, Casley D, Johnston C, Gray L. Effects of drinking on thirst and vasopressin in dehydrated elderly men. Am J Physiol. 1993; 264(5 Pt 2):R877–881.
16 16. Tian Y, Serino R, Verbalis JG. Downregulation of renal vasopressin V2 receptor and aquaporin‐2 expression parallels age‐associated defects in urine concentration. American journal of physiology Renal physiology. 2004; 287(4):F797–805.
17 17. Albert SG, Nakra BR, Grossberg GT, Caminal ER. Vasopressin response to dehydration in Alzheimer's disease. J Am Geriatr Soc. 1989; 37(9):843–847.
18 18. Kayser‐Jones J, Schell ES, Porter C, Barbaccia JC, Shaw H. Factors contributing to dehydration in nursing homes: inadequate staffing and lack of professional supervision. J Am Geriatr Soc. 1999; 47(10):1187–1194.
19 19. Arinzon Z, Feldman J, Peisakh A, Zuta A, Berner Y. Water and sodium disturbances predict prognosis of acute disease in long term cared frail elderly. Arch Gerontol Geriatr. 2005; 40(3):317–326.
20 20. Miller M, Morley JE, Rubenstein LZ. Hyponatremia in a nursing home population. J Am Geriatr Soc. 1995; 43(12):1410–1413.
21 21. Davis PJ, Davis FB. Water excretion in the elderly. Endocrinol Metab Clin North Am. 1987; 16(4):867–875.
22 22. Crowe MJ, Forsling ML, Rolls BJ, Phillips PA, Ledingham JG, Smith RF. Altered water excretion in healthy elderly men. Age Ageing. 1987; 16(5):285–293.
23 23. Schrier RW, Gross P, Gheorghiade M, et al. Tolvaptan, a selective oral vasopressin V2‐receptor antagonist, for hyponatremia. N Engl J Med. 2006; 355(20):2099–2112.
24 24. Liamis G, Milionis H, Elisaf M. A review of drug‐induced hyponatremia. Am J Kidney Dis. 2008; 52(1):144–153.
25 25. Jacob S, Spinler SA. Hyponatremia associated with selective serotonin‐reuptake inhibitors in older adults. Ann Pharmacother. 2006; 40(9):1618–1622.
26 26. Liamis G, Filippatos TD, Elisaf MS. Thiazide‐associated hyponatremia in the elderly: what the clinician needs to know. J Geriatr Cardiol. 2016; 13(2):175–182.
27 27. Hirshberg B, Ben‐Yehuda A. The syndrome of inappropriate antidiuretic hormone secretion in the elderly. Am J Med. 1997; 103(4):270–273.
28 28. Beckett NS, Peters R, Fletcher AE, et al. Treatment of hypertension in patients 80 years of age or older. N Engl J Med. 2008; 358(18):1887–1898.
29 29. Renneboog B, Musch W, Vandemergel X, Manto MU, Decaux G. Mild chronic hyponatremia is associated with falls, unsteadiness, and attention deficits.