Fluid management in patients with traumatic brain injury.

Movement of water between the brain and the intravascular space is dependent on osmotic gradients, which may be established by the acute administration of either hyper- or hypo-osmolar solutions. Mannitol, a hypertonic crystalloid solution, is commonly used to decrease brain water content and reduce intracranial pressure (ICP). Hypertonic saline solutions also decrease brain water and ICP while temporarily increasing systolic blood pressure and cardiac output. Hypo-osmolar solutions, such as 5% dextrose in water, reduce serum sodium and increase brain water and ICP. Colloid solutions exert little influence on either variable. Fluid restriction minimally affects cerebral edema and, if pursued to excess, may result in episodes of hypotension, which may increase ICP and are associated with worse neurologic outcome. Although there is no single best fluid for patients with traumatic brain injury, isotonic crystalloids are widely used and can be justified on a scientific basis.