What should be administered to a patient with diabetes insipidus when sodium levels exceed 150 mEq/L?

In the case of a patient with diabetes insipidus, managing elevated sodium levels is crucial, especially when levels exceed 150 mEq/L, as hypernatremia can lead to serious complications. When sodium levels are high, the goal is to provide adequate hydration without causing rapid shifts in osmolarity that could lead to cerebral edema.

Administering D5W (5% dextrose in water) is appropriate because it effectively provides free water. The dextrose is metabolized quickly, leaving free water that helps to dilute the serum sodium concentration. This approach is ideal for correcting hypernatremia in patients who are unable to concentrate their urine, as is the case with diabetes insipidus.

The other options, while they may pertain to fluid management in various scenarios, do not provide the necessary free water needed to correct hypernatremia due to diabetes insipidus effectively. For instance, normal saline (0.9% NaCl) would not offer free water and could instead increase sodium levels. Half-normal saline (½ NS) could provide some free water but might not be sufficient to tackle significant hypernatremia quickly or safely. Conversely, 3% saline would increase sodium levels further, making it inappropriate for