For asymptomatic patients with hyponatremia, the following treatments may be of use:
Hypovolemic hyponatremia: Administer isotonic saline to replace the contracted intravascular volume (thereby treating the cause of vasopressin release). Patients with hypovolemia secondary to diuretics may also need potassium repletion, which, like sodium, is osmotically active. Correction of volume repletion turns off the stimulus to ADH secretion, so a large water diuresis may ensue, leading to more rapid correction of hyponatremia than desired. If so, hypotonic fluid, such as D5 ½ normal saline, may need to be administered (see below under normovolemic hyponatremia for guidelines).
Hypervolemic hyponatremia: Treat patients who are hypervolemic with salt and fluid restriction, plus loop diuretics, and correction of the underlying condition. The use of a V2 receptor antagonist may be considered.
Normovolemic (euvolemic) hyponatremia: Free water restriction (< 1 L/day) is generally the treatment of choice. There is no role for hypertonic saline in these patients. Base the volume of restriction on the patient's renal diluting capacity. For instance, fluid restriction to 1 L/day, which is enough to raise the serum sodium in some patients, may exceed the renal free water excretion capacity in others, necessitating more severe restriction. This approach is recommended as initial treatment for patients with asymptomatic SIADH.
Acute hyponatremia (duration < 48 hours) can be safely corrected more quickly than chronic hyponatremia. A severely symptomatic patient with acute hyponatremia is in danger from brain edema. In contrast, a symptomatic patient with chronic hyponatremia is more at risk from rapid correction of hyponatremia.
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Cite this: Romesh Khardori. Fast Five Quiz: Hyponatremia Essentials - Medscape - Oct 14, 2019.