The calculation of cerebral perfusion pressure (CPP), with CPP = mean arterial pressure (MAP) - intracranial pressure (ICP), has become the most used estimator of cerebral blow flow. To prevent ischemia due to elevated ICP, current international guidelines recommend maintaining CPP at 60-70 mmHg and ICP below 20 mmHg. However, episodes of brain hypoxia/ischemia, as assessed with brain tissue oxygen pressure (PbtO2) measurements, might occur despite optimization of CPP and ICP, and have been independently associated with poorer patient outcome. PbtO2 values lower than 15 mmHg for more than 30 minutes were shown to be an independent predictor of unfavorable outcome and death. The aggressive treatment of low PbtO2 was associated with improved outcome compared to standard ICP/CPP-directed therapy in cohort studies of severely head-injured patients. On the basis of these findings, it is hypothesized that an early optimization of brain oxygenation, together with keeping ICP and CPP within recommended values, could reduce the volume of vulnerable lesions following severe TBI and possibly improve neurological outcome.