Which statement correctly describes osmotic therapies used for ICP control in TBI?

Which statement correctly describes osmotic therapies used for ICP control in TBI?

• A. Mannitol increases plasma osmolality; hypertonic saline increases serum osmolality and expands intravascular volume; mannitol 0.25-1 g/kg IV; hypertonic saline boluses (e.g., 3% or 23.4%) dosing per protocol
• B. Mannitol decreases plasma osmolality; hypertonic saline increases intracellular water; mannitol 3-5 g/kg; hypertonic saline continuous infusion
• C. Mannitol increases plasma volume; hypertonic saline reduces serum osmolality; mannitol 0.1-0.2 g/kg; hypertonic saline dosing not protocol-based
• D. Mannitol and hypertonic saline have identical effects on osmolality; dosing is the same

Answer: (B)

Osmotic therapies work by raising the osmolality of the blood to pull water out of swollen brain tissue, thereby reducing intracranial pressure. Mannitol and hypertonic saline achieve this with some important differences. Mannitol increases plasma osmolality, drawing water from brain tissue into the vascular space. It is typically given as an IV bolus in a weight-based range around 0.25–1 g/kg. Because mannitol is an osmotic diuretic, it can promote diuresis and potentially lead to volume depletion or renal concerns, so fluid balance and kidney function must be monitored. Hypertonic saline also raises serum osmolality but has the added effect of expanding intravascular volume, which can support blood pressure and cerebral perfusion. It is usually given as hypertonic saline boluses (such as 3% or higher) according to a protocol, or as a controlled infusion with careful monitoring of sodium and osmolality. The statement that is incorrect describes mannitol as decreasing plasma osmolality and hypertonic saline as increasing intracellular water; both ideas contradict how these therapies work. It also mismatches typical dosing practices, since mannitol is not given at 3–5 g/kg and hypertonic saline dosing is generally protocol-driven rather than a simple continuous infusion without safeguards. For effective and safe ICP control, remember: these agents increase serum osmolality to draw water out of the brain, with mannitol as an osmotic diuretic and hypertonic saline as a volume-expanding osmotic agent used per protocol.

Osmotic therapies work by raising the osmolality of the blood to pull water out of swollen brain tissue, thereby reducing intracranial pressure. Mannitol and hypertonic saline achieve this with some important differences.

Mannitol increases plasma osmolality, drawing water from brain tissue into the vascular space. It is typically given as an IV bolus in a weight-based range around 0.25–1 g/kg. Because mannitol is an osmotic diuretic, it can promote diuresis and potentially lead to volume depletion or renal concerns, so fluid balance and kidney function must be monitored.

Hypertonic saline also raises serum osmolality but has the added effect of expanding intravascular volume, which can support blood pressure and cerebral perfusion. It is usually given as hypertonic saline boluses (such as 3% or higher) according to a protocol, or as a controlled infusion with careful monitoring of sodium and osmolality.

The statement that is incorrect describes mannitol as decreasing plasma osmolality and hypertonic saline as increasing intracellular water; both ideas contradict how these therapies work. It also mismatches typical dosing practices, since mannitol is not given at 3–5 g/kg and hypertonic saline dosing is generally protocol-driven rather than a simple continuous infusion without safeguards. For effective and safe ICP control, remember: these agents increase serum osmolality to draw water out of the brain, with mannitol as an osmotic diuretic and hypertonic saline as a volume-expanding osmotic agent used per protocol.