This is a study comparing effects of two hypertonic solutions (mannitol, 6.4% hypertonic saline) on intracranial hypertension, cerebral blood flow, serum/urine osmolarity in patients with increased intracranial pressure caused by traumatic brain injury. The study is conducted during first 72 hours after the injury without any interference with standard medical treatment as performed at the institution. When the hypertonic solution is indicated by caregiver, the study team is informed and performs a set of physiologic bedside measurements including evaluation of cerebral blood flow and changes in plasma and urine osmolarity. The study is noninvasive and the study protocol does not hamper, in any way, standard care of treatment for these patients.