Which action is appropriate in the care of a patient with SIADH?

• A. Increase oral fluids to 2 liters
• B. Restrict oral fluids to 500-1000 mL
• C. Administer hypotonic IV fluids
• D. Encourage free water intake

Answer: (B)

In SIADH, too much antidiuretic hormone causes the kidneys to retain water, leading to dilutional hyponatremia even when the patient looks euvolemic. Because the problem is excess free water, the main nursing action is fluid restriction. Limiting oral intake to about 500–1000 mL per day helps reduce further water retention and allows serum sodium to rise gradually as the excess water is excreted. Increasing fluids or encouraging free-water intake would worsen the hyponatremia, and giving hypotonic IV fluids would further dilute serum sodium. If hyponatremia becomes severe or symptomatic, treatment with hypertonic saline may be indicated under close monitoring, but routine care centers on restricting fluids. Monitor serum sodium and the patient’s mental status, and track intake and output to ensure safe correction.