Purpose: Hyponatremia is a common electrolyte disorder in hospitalized patients. Clinical features, outcome and cost of hyponatremia-associated admission and hospitalization in elderly and very elderly patients are not well known.
Methods: Elderly (>64 years) patients admitted to the emergency department (ED) and hospitalized between January 1, 2010, and December 31, 2010, were evaluated. Hyponatremia was defined as serum sodium level below 135 mmol/L. Hyponatremic patients were divided into two groups: group 1 (n = 150, 65-74 years old) and group 2 (n = 103, >74 years old).
Results: A total of 4,960 patients above 65 years of age admitted to ED and hospitalized were included. Prevalence of ED in group 1 and group 2 was 4.1 % (150/3,651) and 7.8 % (103/1,309), respectively (p < 0.001). Vomiting and diarrhea were the most important complaints. A total of 111 (43.8 %) patients were being treated with renin-angiotensin system (RAS) blockers. Mortality, morbidity and hospital cost increased in parallel to decrease in serum Na(+) level and increase in age. Group 2 subjects had not only higher intensive care need (p < 0.01) and mortality rates (p < 0.01), but also higher hospital cost burden (p < 0.05) compared to group 1. Alzheimer's disease was one of the most common co-morbidity in patients, particularly in group 2 (5.3 % vs. 21.3 %, p < 0.001).
Conclusion: Hyponatremia-associated hospitalization is an important and potentially lethal condition in elderly and very elderly patients. Clinicians should be careful when prescribing RAS blockers and diuretics in elderly patients.