A 62-yrs-old male presents to you with an acute onset of hemiparesis. CT scan reveals an increase in intracranial fluid. Which solution will be most effective in reducing intracranial pressure following a large hemispheric stroke?

Rapid removal of fluid from the brain can be produced by the administration of a fluid that increases the osmotic pressure difference between the brain and the cerebral vessels. The appropriate solution must have a higher osmolarity (that is, greater than 300 mM) and be composed of a solute that is impermeable to the blood- brain barrier Of the solutions listed, only urea and mannitol are hyperosmotic and of these, only mannitol is impermeable to the blood-brain barrier.