Hypotonic hyponatremia Hypotonic hyponatremia Hypoosmolar hyponatremia is a condition where hyponatremia associated with a low plasma osmolality. The term "hypotonic hyponatremia" is also sometimes used. When the plasma osmolarity is low, the extracellular fluid volume status may be in one of three states: low volume, normal volume, or high volume. Loss of water is accompanied by loss of sodium. Treat underlying cause and give IV isotonic saline. It is important to note that sudden restoration of blood volume to normal will turn off the stimulus for continued ADH secretion. Hence, a prompt water diuresis will occur. This can cause a sudden and
Hypotonic hyponatremia ADH secretion. As a result, the kidneys of such patients recover water and produce a fairly concentrated urine. Treatment is simple (if not without risk) — simply restore the patient's blood volume, thereby turning off the stimulus for ongoing ADH release and water retention. It is worth considering separately, the hyponatremia that occurs in the setting of diuretic use. Patients taking diuretic medications such as furosemide (Lasix), hydrochlorothiazide, chlorthalidone, etc., become volume depleted. That is to say that their diuretic medicine, by design, has caused their kidneys to produce more urine than they would otherwise make. This extra urine represents