Hyponatremia

Abstract

Hyponatremia, defined as a serum sodium level of <135 mEq/L, is a common electrolyte imbalance in clinical practice that can lead to considerable morbidity and mortality if not recognized and treated appropriately. Assessing and correcting hyponatremia can be quite complex, as there are numerous potential etiologies that enact through a variety of different pathophysiological mechanisms. Furthermore, the process may be either acute or chronic in nature, and the resulting symptoms can range from being seemingly nonexistent to quite severe. In evaluating hyponatremia, it is typically classified relative to the extracellular fluid volume status: it is either hypovolemic, euvolemic, or hypervolemic hyponatremia. This classification as well as the chronicity of the hyponatremia and severity of the symptoms are used to guide management and determine how quickly it needs to be corrected. Failure to treat profound hyponatremia in a timely fashion can lead to mortality from brain edema; however, raising the serum sodium level too quickly can cause osmotic demyelination syndrome. Patients with hyponatremia should be evaluated and treated with a careful, systematic approach to avoid such adverse outcomes.