A patient with increased ICP has mannitol prescribed. Which option best indicates that the drug is achieving its desired therapeutic effect?

A patient with increased ICP has mannitol prescribed. Which option best indicates that the drug is achieving its desired therapeutic effect?

• A. Urine output increases from 30 mL to 50 mL/hour.
• B. The LOC improves.
• C. Blood pressure remains less than 150/90 mm Hg.
• D. No crackles are auscultated in the lung fields.

Answer: (B)

The main idea is that the goal of giving mannitol for increased intracranial pressure is to lower the pressure inside the skull, which should improve brain function. Mannitol works as an osmotic agent: it draws water out of swollen brain tissue into the bloodstream, reducing cerebral edema and ICP. When ICP drops, neurologic function often improves, so an improved level of consciousness is the clearest, most direct sign that the drug is working. Urine output increasing shows that diuresis is occurring, but it doesn’t necessarily reflect changes in intracranial pressure. Blood pressure staying under a certain limit isn’t a direct indicator of ICP either. Absence of crackles in the lungs suggests no pulmonary edema, not that ICP has decreased. So the best indication that mannitol is achieving its desired effect is an improvement in the patient’s level of consciousness.

The main idea is that the goal of giving mannitol for increased intracranial pressure is to lower the pressure inside the skull, which should improve brain function. Mannitol works as an osmotic agent: it draws water out of swollen brain tissue into the bloodstream, reducing cerebral edema and ICP. When ICP drops, neurologic function often improves, so an improved level of consciousness is the clearest, most direct sign that the drug is working.

Urine output increasing shows that diuresis is occurring, but it doesn’t necessarily reflect changes in intracranial pressure. Blood pressure staying under a certain limit isn’t a direct indicator of ICP either. Absence of crackles in the lungs suggests no pulmonary edema, not that ICP has decreased. So the best indication that mannitol is achieving its desired effect is an improvement in the patient’s level of consciousness.