In syndrome of inappropriate antidiuretic hormone (SIADH) with a serum sodium of 112 mEq/L, which protocol prescription should the nurse implement first?

• A. Restrict fluids to zero
• B. Obtain serum sodium level every 4 hours
• C. Administer IV hypertonic saline
• D. Initiate seizure precautions

Answer: (B)

In this situation, the priority is to monitor the patient’s electrolyte status closely to guide treatment and prevent risks from rapid changes. With severe hyponatremia (112 mEq/L) in SIADH, obtaining serum sodium levels at frequent intervals provides essential data about the current status and how quickly sodium is changing, which directly informs the safest plan of care. Checking the sodium every few hours helps ensure that any interventions (such as fluid restriction or hypertonic saline) are adjusted appropriately and that correction does not occur too quickly, which could cause osmotic demyelination.

Fluid restriction is a common therapeutic measure in SIADH, but it should be implemented with guidance and orders, not as the immediate first action when you don’t yet have current lab data to tailor the plan. Administering IV hypertonic saline is reserved for planned treatment by a clinician and requires careful monitoring and orders to avoid overcorrection. Seizure precautions are important if there are symptoms or high risk, but they’re not the initial step in establishing the patient’s current electrolyte status and need for specific therapy.