Disorders of Plasma Sodium - Causes, Consequences, and Correction

Human cells dwell in salt water. Their well-being depends on the ability of the body to regulate the salinity of extracellular fluids. By controlling water intake and excretion, the osmoregulatory system normally prevents the plasma sodium concentration from straying outside its normal range (135 to 142 mmol per liter). Failure of the system to regulate within this range exposes cells to hypotonic or hypertonic stress. This review considers the causes and consequences of an abnormal plasma sodium concentration and offers a framework for correcting it. © 2015 Massachusetts Medical Society.