To define hyponatremia, discuss its incidence and epidemiology, and summarize the frequency and prognostic implications of hyponatremia in selected clinical conditions.Summary:
Hyponatremia is the most common electrolyte abnormality encountered in clinical practice. Hyponatremia is commonly defined as a serum sodium concentration of <136 mEq/L. There are 3 different types of hyponatremia: hypovolemia, euvolemia, and hypervolemia. Epidemiologic studies reveal that hyponatremia is a common problem in hospitalized patients whether it is present at admission or is hospital acquired. The disorder increases the risk of admission to the intensive care unit, hospital length of stay, and morbidity and mortality. Hyponatremia appears to be a marker for severe underlying disease with a poor prognosis. Congestive heart failure, pneumonia, cirrhosis, and neurologic disease are among the serious clinical conditions known to be associated with hyponatremia. Chronic hyponatremia presents its own set of challenges; even in mild disease that is often asymptomatic, patients are at heightened risk for falls, gait disturbances, attention deficits, and fracture.Conclusion:
Hyponatremia is the most common electrolyte disorder encountered in clinical practice and is associated with significant morbidity and mortality, especially at lower serum sodium concentrations. The disorder has a substantial impact on hospital length of stay with a direct impact on health care costs. Further, as this discussion illustrates, hyponatremia represents a significant clinical burden in all forms - mild, moderate, and severe - with subsequent clinical consequences.