Which client would the nurse assess first when a medication order for mannitol (Osmitrol) is given?

• A. A 67-year-old client with type 1 diabetes mellitus
• B. A 21-year-old client with a head injury
• C. A 47-year-old client with anuria
• D. A 55-year-old client receiving cisplatin to treat ovarian cancer

Answer: (C)

Mannitol works by creating an osmotic gradient in the kidney to promote diuresis, and it is excreted by the kidneys. If a patient isn’t producing urine (anuria), the drug cannot be eliminated, which can lead to accumulation, fluid overload (pulmonary edema), electrolyte and osmolar imbalances, and worsening renal function. Because of this, assessing renal function and urine output takes highest priority before administering mannitol.

Among the options, the client with anuria poses the greatest safety risk if mannitol is given, so the nurse should assess that patient's status first by checking urine output, renal function tests, electrolytes, and signs of fluid overload. After confirming renal function is adequate (or deciding it’s not), the nurse would proceed with caution for the other clients, such as the head-injury patient who may benefit from reduced intracranial pressure, while continuing to monitor closely.