Application of established pathophysiologic processes brings greater clarity to diagnosis and treatment of hyponatremia

Figure 6 Changes in urine osmolality and serum sodium concentration during isotonic infusion in a hyponatremic patient with a hip fracture without clinical evidence of cerebral disease. The low Uosm at baseline reflected a low sodium intake when UNa was only 6 mEq/L and a weakened medullary solute concentration, which increased rapidly with a marked increase in Uosm after 4 h of saline infusion. Plasma antidiuretic hormone (ADH) was increased with increased plasma renin and aldosterone levels at baseline and ADH level was undetectable when the urine was dilute 13 h with increase in serum sodium to 138 mEq/L within 48 h after initiation of isotonic saline infusion. Printed with permission, Ref. [12].