Which statement best describes the mechanism of mannitol in ICP management?

Which statement best describes the mechanism of mannitol in ICP management?

• A. Increase CSF production.
• B. Create an osmotic gradient that draws water from brain tissue into the bloodstream, lowering ICP.
• C. Decrease cerebral blood flow.
• D. Cause renal vasodilation leading to reduced intravascular volume.

Answer: (B)

Osmotic therapy lowers intracranial pressure by pulling water out of swollen brain tissue into the bloodstream. Mannitol raises the osmolality of plasma relative to brain tissue and CSF, so water follows the osmotic gradient from the brain into the intravascular space, reducing brain edema and the pressure inside the skull. This effect can improve cerebral perfusion and help protect brain tissue, but it relies on an intact blood-brain barrier; if the barrier is broken, mannitol may cross into the brain and potentially worsen edema, so monitoring is essential. In practice, you also watch for osmotic diuresis and electrolyte shifts, and you’re mindful of the risk of rebound ICP if therapy is stopped too quickly.

Osmotic therapy lowers intracranial pressure by pulling water out of swollen brain tissue into the bloodstream. Mannitol raises the osmolality of plasma relative to brain tissue and CSF, so water follows the osmotic gradient from the brain into the intravascular space, reducing brain edema and the pressure inside the skull. This effect can improve cerebral perfusion and help protect brain tissue, but it relies on an intact blood-brain barrier; if the barrier is broken, mannitol may cross into the brain and potentially worsen edema, so monitoring is essential. In practice, you also watch for osmotic diuresis and electrolyte shifts, and you’re mindful of the risk of rebound ICP if therapy is stopped too quickly.