Hyponatremia

Excerpt

Hyponatremia is defined as a serum sodium concentration of less than 135 mEq/L but can vary to some extent depending upon the set values of varied laboratories. Hyponatremia is a common electrolyte abnormality caused by an excess of total body water in comparison to that of the total body sodium content. Edelman approved of the fact that serum sodium concentration does not depend on total body sodium but is determined by the ratio of total body solutes (e.g., total body sodium and total body potassium) to total body water. Hyponatremia represents an imbalance in this ratio where total body water is more than total body solutes. Total body water (TBW) has two main compartments, extracellular fluid (ECF), accounting for one-third, and intracellular fluid (ICF), accounting for the remaining two-thirds. Sodium is the major solute of ECF, and potassium for ICF.