title: Cerebral perfusion pressure and intracranial pressure are not surrogates for brain tissue oxygenation in traumatic brain injury.
abstract: OBJECTIVE
  Utilization of brain tissue oxygenation (pBtO(2)) is an important but controversial variable in the treatment of traumatic brain injury (TBI). We evaluated the correlation between pBtO(2)/CPP and pBtO(2)/ICP and determined the parameter most closely related to survival.
  
  
  METHODS
  Consecutive, adult patients with severe TBI and pBtO(2) monitors were retrospectively identified. Time-indexed measurements of pBtO(2), CPP and ICP were collected and correlation coefficients were determined. Patients were then stratified according to survival and pBtO(2), CPP and ICP values were compared between groups.
  
  
  RESULTS
  There were 4169 time-indexed data points (i.e., pBtO(2) with respective CPP and ICP values) in 15 patients. The cohort consisted of a mean age of 37±17 years, ISS of 27±7 and GCS of 4.5±1.5. Survival was 53% (8/15). In a normal regression models, neither the ICP (p=0.58) nor the CPP (p=0.71) predict pBtO(2) significantly. There was a significant difference in pBtO(2) in survivors (31.5±3.1 vs. 25.2±4.8, p=0.010) but not in CPP or ICP. Survivors had a lower proportion of time with pBtO(2)<25 mmHg [20% (3.4-44.6) vs. 40% (16.2-89), p=0.049]. In contrast, survivors had a greater proportion of time with CPP<70 and no difference in the proportion of time with and ICP>20.
  
  
  CONCLUSIONS
  CPP and ICP should not be used as surrogates for pBtO(2) since cerebral oxygenation varies independently of cerebral hemodynamics and pressures. Brain tissue oxygen monitoring in patients with TBI provides unique information regarding cerebral oxygenation the utility of which remains to be fully described.
  
  
  CONCLUSIONS
  CPP and ICP are not surrogates for pBtO(2). Brain tissue oxygenation monitoring provides unique information for the treatment of traumatically injured patients.
authors: Department of Trauma/Critical Care, Medical University of South Carolina, GRMERC/MSU Surgical Critical Care Fellowship, Charleston, SC 29425, USA. evsurgery@gmail.com
authors: Evert A
authors: EA
authors: Eriksson
authors: Jeffrey F
authors: JF
authors: Barletta
authors: Bryan E
authors: BE
authors: Figueroa
authors: Bruce W
authors: BW
authors: Bonnell
authors: Wayne E
authors: WE
authors: Vanderkolk
authors: Karen J
authors: KJ
authors: McAllen
authors: Mickey M
authors: MM
authors: Ott
mesh_terms: D000328:Adult; D000368:Aged; D001930:Brain Injuries / Q000401:mortality / Q000503:physiopathology*; D015331:Cohort Studies; D005260:Female; D006439:Hemodynamics; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods*; D010100:Oxygen / Q000502:physiology*; D012189:Retrospective Studies
chemical_list: D010100:Oxygen