title: Continuous assessment of cerebrovascular autoregulation after traumatic brain injury using brain tissue oxygen pressure reactivity.
abstract: OBJECTIVE
  To evaluate whether two newly developed indexes of brain tissue oxygen pressure reactivity (ORx and bPtio2) provide information on the status of cerebrovascular autoregulation after traumatic brain injury. This was accomplished by analyzing the relationship between these indexes and an index of cerebrovascular pressure reactivity (PRx). PRx is an established parameter for estimation of cerebrovascular autoregulation.
  
  
  METHODS
  Retrospective analysis of prospectively collected data.
  
  
  METHODS
  Neurosurgical intensive care unit of a university hospital.
  
  
  METHODS
  Twenty-seven patients suffering from severe traumatic brain injury.
  
  
  METHODS
  Continuous monitoring of mean arterial blood pressure, intracranial pressure, cerebral perfusion pressure, and partial pressure of brain tissue oxygen (Ptio2) was performed for an average of 6.5 days. ORx was calculated as a moving correlation coefficient between values of cerebral perfusion pressure and Ptio2. The bPtio2 was calculated as a moving value of the slope of the linear regression function between cerebral perfusion pressure and Ptio2. PRx was calculated as a moving correlation coefficient between values for intracranial pressure and mean arterial blood pressure. Outcome was assessed at 6 months after traumatic brain injury (Glasgow Outcome Scale).
  
  
  RESULTS
  Both ORx and bPtio2 correlated significantly with PRx (r=.55 for ORx, r=.52 for bPtio2, p<.01). PRx and ORx showed a significantly negative correlation to the monitored Ptio2 values (r=-.42 for PRx, r=-.41 for ORx, p<.05) and outcome (r=-.52 for PRx, r=-.62 for ORx, p<.01), whereas bPtio2 did not.
  
  
  CONCLUSIONS
  ORx and, to a lesser extent, bPtio2 correlated with the autoregulatory marker PRx and provide additional information about the status of cerebrovascular autoregulation after traumatic brain injury. The data also suggested that patients with impaired autoregulation are at increased risk for secondary cerebral hypoxia.
authors.affiliation: Department of Neurosurgery, University of Leipzig, Leipzig, Germany. jaem@medizin.uni-leipzig.de
authors.forename: Matthias
authors.initials: M
authors.lastname: Jaeger
authors.forename: Martin U
authors.initials: MU
authors.lastname: Schuhmann
authors.forename: Martin
authors.initials: M
authors.lastname: Soehle
authors.forename: Jürgen
authors.initials: J
authors.lastname: Meixensberger
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001794:Blood Pressure; D001930:Brain Injuries / Q000175:diagnosis / Q000378:metabolism / Q000503:physiopathology*; D002560:Cerebrovascular Circulation; D005260:Female; D005500:Follow-Up Studies; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D010101:Oxygen Consumption / Q000502:physiology*; D012189:Retrospective Studies; D015599:Trauma Severity Indices