The Genesis of Hyponatremia Associated with Marked Overhydration and Water Intoxication

Abstract

Prolonged overhydration and hyponatremia have been produced in 10 patients with use of Pitressin Tannate in Oil. Balance studies have shown that in patients who developed moderate hyponatremia, the drop in serum sodium could be explained by water retention. In patients who developed severe water intoxication, the very low levels of serum sodium (100-114 mEq./L.) could not be entirely accounted for by changes in salt and water balance. Certain patients failed to develop severe water intoxication although an equivalent degree of overhydration was achieved. In these subjects, further overhydration was limited by intermittent episodes of low solute diuresis. This diuretic escape from Pitressin effect has been evaluated by measurement of U/P osmolar ratio on 24-hour urine specimens as well as T^cH₂O during hypertonic mannitol infusion. Defects in both aspects of renal concentration were observed, although they were not necessarily coexistent.