Abstract
Hyponatremia is the most common electrolyte disorder, commonly affecting older hospitalized individuals; however, the literature is not clear regarding its effect on mortality. The aim of this 2-year observational prospective cohort study was to evaluate the mortality and re-admission rates, the clinical and laboratory characteristics and the causes of hyponatremia in patients older than 65 years admitted with a corrected serum sodium of 130 mEq/L or less in an internal medicine ward of a tertiary Greek university hospital. During the observation period, 138 patients (mean age 80.5 years, 36.2% male) fulfilled the inclusion criteria and were prospectively followed for 1 year after admission. Symptoms of hyponatremia were present in 59.4% of patients. Hypovolemia was the main sole cause of hyponatremia, but in about one third of patients, hyponatremia was multifactorial. Only a low proportion of patients (12.3%) fulfilled the criteria of the syndrome of inappropriate antidiuresis (SIAD) at admission according to the current guidelines. The re-admission rates at 3- and 12-months following discharge was 34.2% and 51.8%, respectively. Mortality during hospitalization was 17.4% and was higher compared to non-hyponatremic admitted older patients, while the total mortality at 1 year after admission was 28.3%, indicating that hyponatremia at admission is a marker of significant mortality during and after hospitalization in elderly patients.
Highlights
Hyponatremia is the most common electrolyte disorder in both community and hospitalized patients and is associated with adverse outcomes and mortality, especially when it is moderate or severe [1].Its prevalence is even higher in older individuals due to physiologic changes that involve reduced total body water volume and lower urine concentrating ability [2]
A common cause of hyponatremia with a problematic diagnosis in older individuals is the syndrome of inappropriate antidiuresis (SIAD), which is associated with water retention and dilutional hyponatremia due to excessive antidiuretic hormone (ADH) excretion
SIAD is reported to be more common in older individuals and its diagnosis may be problematic due to multifactorial etiology [5,6]
Summary
Its prevalence is even higher in older individuals due to physiologic changes that involve reduced total body water volume and lower urine concentrating ability [2]. The diagnostic evaluation of hyponatremia involves the assessment of the patient volume status, which can be quite subjective and unreliable, especially in older individuals [3]. A common cause of hyponatremia with a problematic diagnosis in older individuals is the syndrome of inappropriate antidiuresis (SIAD), which is associated with water retention and dilutional hyponatremia due to excessive antidiuretic hormone (ADH) excretion. SIAD is reported to be more common in older individuals and its diagnosis may be problematic due to multifactorial etiology [5,6]
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