This will create trancellular osmotic gradients and water movement out of cells. The increase in ECF water content will dilute the sodium and lower sodium concentration. Salt wasting, Adrenal Insuff, GU obstruction Hypotonic hyponatremia indicates relative excess of water in relation to sodium. Plasma sodium concentration provides no indication of total body sodium content. Thus, hyponatremia can be associated with normal, increased or decreased total body sodium.
Plasma sodium represents the balance of water intake and water excretion.
Since the renal capacity to excrete water is so great hyponatremia rarely occurs from excessive water intake alone. Inadequate renal plasma flow and GFR Inadequate delivery of filtrate from the proximal tubule Decreased generation of free water in the Loop of Henle and distal tubule. Enhanced water reabsorption of water in the collecting duct. Classification of Hypotonic Hyponatremia Hypovolemic Hyponatremia Isovolemic Hyponatremia Hypervolemic Hyponatremia Hypovolemic Hyponatremia Pathogenesis Sodium and water losses are replaced with water alone. Decrease in arterial blood volume stimulates release of AVP, which in turn enhances water reabsorption in collecting duct.