A nurse is caring for a client who has syndrome of inappropriate antidiuretic hormone (SIADH) and a sodium level of 125 mEq/L. Which of the following interventions should the nurse anticipate?

Choice A reason: Administering desmopressin (DDAVP), a synthetic antidiuretic hormone, is contraindicated in SIADH, as it exacerbates water retention, worsening hyponatremia. Desmopressin is used for diabetes insipidus, where ADH is deficient, not SIADH, where ADH excess causes fluid overload and sodium dilution. Choice B reason: Maintaining an IV infusion of 5% dextrose water is inappropriate for SIADH, as it adds free water, further diluting serum sodium and worsening hyponatremia (125 mEq/L). Hypertonic saline or fluid restriction is needed to correct sodium imbalance, making this intervention incorrect. Choice C reason: Initiating fluid restriction (e.g., 1,000 mL/day) is appropriate for SIADH, as it reduces water intake, allowing the kidneys to excrete excess water, raising serum sodium levels. This corrects hyponatremia (125 mEq/L) caused by ADH-driven water retention, making it the primary intervention. Choice D reason: Providing a low sodium diet is not indicated for SIADH, as the primary issue is water retention, not sodium intake. Restricting sodium could worsen hyponatremia by further reducing serum sodium availability, making fluid restriction a more effective intervention for this condition.