There is growing evidence in the literature indicating that ICP and Cerebral Perfusion Pressure measurements may not be sufficient in the management of elevated ICP. Based on this evidence, monitoring of partial brain tissue oxygenation has gain acceptance among neurosurgeons and neurointensivists, and has become a standard of care monitor in some centers across the country. There is, however, insufficient information in the literature describing the effects of hyperosmolar medications on regional brain tissue oxygenation.