title: Brain tissue oxygenation and cerebral metabolic patterns in focal and diffuse traumatic brain injury.
abstract: BACKGROUND
  Neurointensive care of traumatic brain injury (TBI) patients is currently based on intracranial pressure (ICP) and cerebral perfusion pressure (CPP) targeted protocols. There are reasons to believe that knowledge of brain tissue oxygenation (BtipO2) would add information with the potential of improving patient outcome. The aim of this study was to examine BtipO2 and cerebral metabolism using the Neurovent-PTO probe and cerebral microdialysis (MD) in TBI patients.
  
  
  METHODS
  Twenty-three severe TBI patients with monitoring of physiological parameters, ICP, CPP, BtipO2, and MD for biomarkers of energy metabolism (glucose, lactate, and pyruvate) and cellular distress (glutamate, glycerol) were included. Patients were grouped according to injury type (focal/diffuse) and placement of the Neurovent-PTO probe and MD catheter (injured/non-injured hemisphere).
  
  
  RESULTS
  We observed different patterns in BtipO2 and MD biomarkers in diffuse and focal injury where placement of the probe also influenced the results (ipsilateral/contralateral). In all groups, despite fairly normal levels of ICP and CPP, increased MD levels of glutamate, glycerol, or the L/P ratio were observed at BtipO2 <5 mmHg, indicating increased vulnerability of the brain at this level.
  
  
  CONCLUSIONS
  Monitoring of BtipO2 adds important information in addition to traditional ICP and CPP surveillance. Because of the different metabolic responses to very low BtipO2 in the individual patient groups we submit that brain tissue oximetry is a complementary tool rather than an alternative to MD monitoring.
authors.affiliation: Section of Neurosurgery, Department of Neuroscience, Uppsala University , Uppsala , Sweden.
authors.forename: Karlis
authors.initials: K
authors.lastname: Purins
authors.affiliation: Section of Neurosurgery, Department of Neuroscience, Uppsala University , Uppsala , Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Lewén
authors.affiliation: Section of Neurosurgery, Department of Neuroscience, Uppsala University , Uppsala , Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Hillered
authors.affiliation: Section of Neurosurgery, Department of Neuroscience, Uppsala University , Uppsala , Sweden.
authors.forename: Tim
authors.initials: T
authors.lastname: Howells
authors.affiliation: Section of Neurosurgery, Department of Neuroscience, Uppsala University , Uppsala , Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Enblad
keywords: Neurovent-PTO; brain tissue oxygenation; cerebral ischemia; cerebral metabolism; traumatic brain injury