Neurologic Critical Care Opposed effects of hypertonic saline on contusions and noncontused brain tissue in patients with severe traumatic brain injury*

Hypertonic saline (HS) used at various concentration (3– 23.4%) has been consistently shown to decrease intracranial pressure (ICP) and cerebral water content in human traumatic brain injury (TBI) (1, 2). The mean pressure drop is usually 40% (3). HS is still used as a second-line therapy in adults (4) and children (5) with exhausted response to mannitol and barbiturates. Experimentally, HS is more efficient in reducing ICP than equiosmolar doses of mannitol (6). In addition, HS might also be beneficial to the immune system by modulating cellular immune function after trauma and restoring the immune function of healthy T cells (7–9). However, the patient population that is most likely to respond to HS needs to be further defined. From a theoretical point of view, it can be expected that HS is effective only in the areas of the brain where the blood-brain barrier (BBB) is still functional after trauma. There are numerous arguments in favor of a profound alteration of the BBB in contusion appearing areas on CT (10–12) in part secondary to regional ischemia (11, 13– 15). This study was thus designed to evaluate the regional effects of hypertonic saline on contused and noncontused brain tissue after TBI. Our hypothesis was that HS would increase the volume of brain contusion while decreasing the volume of the noncontused areas. This was done by comparing global and regional brain volume, weight, and specific gravity, as assessed by a recently described software (16) computing these variables out of computed tomography (CT) images, before and after HS bolus administration in a series of 14 patients with severe head trauma.