Which statement best compares mannitol and hypertonic saline as therapies for intracranial hypertension?

Which statement best compares mannitol and hypertonic saline as therapies for intracranial hypertension?

• A. Mannitol draws free water osmotically; hypertonic saline increases intravascular osmolality; both reduce ICP.
• B. Mannitol increases intravascular volume; hypertonic saline causes hyponatremia; both increase ICP.
• C. Mannitol reduces cerebral perfusion; hypertonic saline has no effect on edema; both do not affect ICP.
• D. Hypertonic saline is contraindicated in intracranial hypertension; Mannitol is preferred for all cases.

Answer: (A)

Osmotic therapies reduce intracranial pressure by creating a gradient that pulls water out of swollen brain tissue into the bloodstream. Mannitol works by raising the osmolality of the plasma; as plasma becomes more concentrated, water moves from the brain's interstitial and intracellular spaces into the vascular compartment, decreasing brain volume and ICP. Hypertonic saline accomplishes a similar effect by increasing intravascular osmolality, which also draws water from brain tissue into the blood, leading to lower ICP. This description captures why these two treatments both lower ICP, even though they act through slightly different routes. Understandably, mannitol’s effect can be influenced by the integrity of the blood–brain barrier and it can cause diuresis and potential volume shifts, while hypertonic saline also carries risks like hypernatremia and volume overload. Still, their shared mechanism—moving water out of the brain by increasing plasma osmolality—is the reason they are both effective options for intracranial hypertension.

Osmotic therapies reduce intracranial pressure by creating a gradient that pulls water out of swollen brain tissue into the bloodstream. Mannitol works by raising the osmolality of the plasma; as plasma becomes more concentrated, water moves from the brain's interstitial and intracellular spaces into the vascular compartment, decreasing brain volume and ICP. Hypertonic saline accomplishes a similar effect by increasing intravascular osmolality, which also draws water from brain tissue into the blood, leading to lower ICP. This description captures why these two treatments both lower ICP, even though they act through slightly different routes.

Understandably, mannitol’s effect can be influenced by the integrity of the blood–brain barrier and it can cause diuresis and potential volume shifts, while hypertonic saline also carries risks like hypernatremia and volume overload. Still, their shared mechanism—moving water out of the brain by increasing plasma osmolality—is the reason they are both effective options for intracranial hypertension.