Management
Hypotonic hyponatremia accounts for most clinical cases of hyponatremia and can be treated with fluids. Acute hyponatremia (duration < 48 hours) can be safely corrected more quickly than chronic hyponatremia. The treatment of hypertonic and pseudohyponatremia is directed at the underlying disorder in the absence of symptoms.
Intravenous fluids and water restriction
Administer isotonic saline to patients who are hypovolemic to replace the contracted intravascular volume. Patients with hypovolemia secondary to diuretics may also need potassium repletion, which, like sodium, is osmotically active.
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.
For euvolemic, asymptomatic hyponatremic patients, free water restriction (< 1 L/day) is generally the treatment of choice. There is no role for hypertonic saline in these patients.
When treating patients with overtly symptomatic hyponatremia (eg, seizures, severe neurologic deficits), hypertonic (3%) saline should be used.
Pharmacologic treatment
Conivaptan, a V1A and V2 vasopressin receptor antagonist, is available only for intravenous use and is approved for use in the hospital setting for euvolemic and hypervolemic hyponatremia. It is contraindicated in hypovolemic patients. It induces both a water and sodium diuresis with improvement in plasma sodium levels.