In SIADH with hyponatremia, what is the underlying mechanism and a typical nursing consideration?

• A. Decreased ADH causing dehydration; fluid restriction
• B. Excess ADH causing water retention and dilutional hyponatremia; monitor sodium, fluid restriction, careful isotonic/hypertonic saline if severe with physician oversight
• C. High aldosterone causing salt loss; give diuretics
• D. Increased natriuretic peptides causing diuresis; give IV fluids

Answer: (D)

In SIADH, the problem is too much antidiuretic hormone prompting the kidneys to retain water, which dilutes the blood sodium and lowers serum osmolality—this is dilutional hyponatremia. The nursing plan centers on limiting free water intake (fluid restriction) and closely monitoring sodium levels, neurologic status, and fluid balance. In mild cases, fluid restriction and observation may suffice, but in more severe situations or with symptoms like confusion or seizures, hypertonic saline may be used under physician oversight, with careful monitoring to avoid overly rapid correction. It’s not due to reduced ADH, excess aldosterone causing salt loss, or natriuretic peptide–driven diuresis; those mechanisms would lead to different problems (dehydration or salt wasting) rather than the water-retaining, hyponatremic state seen in SIADH.