After administering mannitol, what vital sign is critical for the nurse to monitor?

Mannitol is an osmotic diuretic used primarily to reduce intracranial pressure and treat acute renal failure by increasing osmotic pressure in the kidney tubules. One of the significant effects of mannitol is the increase in urine output, which can lead to rapid fluid shifts and changes in hemodynamics.

Monitoring blood pressure is critical after administering mannitol due to the potential for hypotension as a result of fluid loss. As mannitol draws water into the renal tubules, it causes diuresis, which can lead to a reduction in blood volume and subsequently lower blood pressure. With these changes, it is important for the nurse to closely observe blood pressure to ensure it remains within a safe range and to intervene appropriately if significant drops occur.

In contrast, while respiratory rate, heart rate, and oxygen saturation are important vital signs in general patient monitoring, they do not directly correlate with the immediate adverse effects expected from mannitol treatment. Therefore, blood pressure stands out as the most critical vital sign to monitor in this scenario.