Inclusion Criteria:  Age limits met at the time of injury and admission Participants with moderate to severe traumatic brain injury defined as a Glasgow Coma Scale Score of 3-12 (lowest score in the first 24 hours after injury). Individuals requiring craniotomy and/or evacuation of intracranial hemorrhage may be included.  Exclusion Criteria:  Anoxia/ischemia as a significant portion of injury, including near-drowning Non-accidental traumatic brain injury (i.e., assault, abuse) Penetrating injury including gunshot wounds Pregnancy Any condition that in the opinion of the Pediatric Intensive Care Unit or neurosurgery medical staff warrants exclusion from the study