Osmotic therapy: fact and fiction.

This review examines the available data on the use of osmotic agents in patients with head injury and ischemic stroke, summarizes the physiological effects of osmotic agents, and presents the leading hypotheses regarding the mechanism by which they reduce ICP. Finally, it addresses the validity of the following commonly held beliefs: mannitol accumulates in injured brain; mannitol shrinks only normal brain and can increase midline shift; osmolality can be used to monitor mannitol administration; mannitol should be not be administered if osmolality is >320 mOsm; and hypertonic saline is equally effective as mannitol.