Clinical Significance

Sodium is the major cation of extracellular fluid; it plays an essential role in the normal distribution of water and in the maintenance of osmotic pressure in extracellular fluid compartments.  Decreased levels of Na+ may be caused by an excessive use of diuretics, prolonged vomiting, a decrease in the intake of sodium in the diet, and metabolic acidosis.  Increased levels of Na+ may be found in Cushing’s syndrome, severe dehydration, or in high levels of salt intake without an adequate supply of water.