Mechanical forces result in shearing and compression of neuronal and vascular tissue at the moment of impact a series of pathology events may then lead to further brain injury. This secondary injury may be amenable to intervention and is worsened by secondary physiological insults. Various risk factors for poor outcome after TBI have been identified. Most of these are fixed at the time of injury such as age, gender, mechanism of injury and presenting signs, but some as hypotension and hypoxia are potential areas for medical intervention.