A client is being treated for syndrome of inappropriate antidiuretic hormone (SIADH). On examination, the client has a weight gain of 4.4 lbs (2 kg) in 24 hours and an elevated blood pressure. Which intervention should the nurse implement first?

A. Obtaining serum creatinine levels is important but not an immediate intervention.B. Monitoring sodium intake is essential but not the first step in acute management.C. Administering a diuretic can help manage the fluid retention and reduce blood pressure, addressing the immediate concern of fluid overload.D. Measuring ankle circumference is part of monitoring fluid status but does not address the immediate need to reduce fluid overload.