Serum sodium concentration and serum osmolarity normally are maintained under control involving stimulation of thirst, secretion of antidiuretic hormone (ADH), and renal andling of filtered sodium.

Extended Definition:

Significant hyponatremia is relatively uncommon and nonspecific in presentation; irreparable harm can occur if abnormal serum sodium levels are corrected too quickly or too slowly.

  • Hypovolemic hyponatremia: Total body water (TBW) decreases, total body sodium (Na+) decreases to a greater extent. The extracellular fluid (ECF) volume is decreased.
  • Euvolemic hyponatremia: TBW increases while total sodium remains normal. The ECF volume is increased minimally to moderately but without the resence of edema.
  • Hypervolemic hyponatremia: Total body sodium increases, and TBW increases to a greater extent. The ECF is increased markedly, with the presence of edema.
  • Redistributive hyponatremia: Water shifts from the intracellular to the extracellular compartment, with a resultant dilution of sodium. The TBW and total body sodium are unchanged. This condition occurs with hyperglycemia or administration of mannitol.
  • Pseudohyponatremia: The aqueous phase is diluted by excessive proteins or lipids. The TBW and total body sodium are unchanged. This condition is seen with hypertriglyceridemia and multiple myeloma.
Located in: General

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