title: Temporal changes in cerebral tissue oxygenation with cerebrovascular pressure reactivity in severe traumatic brain injury.
abstract: OBJECTIVE
  To investigate the temporal relationship between cerebrovascular pressure reactivity and brain tissue oxygenation in patients with severe head injury.
  
  
  METHODS
  In 40 patients, brain tissue oxygenation and intracranial pressure were monitored. Time-averaged values for intracranial pressure (ICP), mean arterial pressure (MAP), cerebral perfusion pressure (CPP) and brain tissue oxygenation (PtiO2) were computed. The pressure reactivity index (PRx) was calculated. The mean values of the variables were obtained at the 6-h and 72-h post-injury time points, and the difference between the two time points for each of the variables was denoted as delta (delta).
  
  
  RESULTS
  Of the 40 patients, 32 were survivors and 8 were non-survivors. Statistically significant differences were present between these two groups with regard to deltaMAP (p = 0.013), ICP at 6 h (p = 0.027), CPP at 72 h (p = 0.018), deltaCPP (p = 0.033), PRx at 6 h (p = 0.029), PRx at 72 h (p = 0.002), PtiO2 at 72 h (p < 0.0005) and deltaPtiO2 (p = 0.023) values, reflecting an improvement with time in survivors and a deterioration with time in non-survivors. In non-survivors, the magnitude of change in PtiO2 and CPP with time correlated in a negative linear fashion (p = 0.042 and 0.029, respectively) with the change in PRx with time, whereas no such relationship was seen in survivors.
  
  
  CONCLUSIONS
  The severity of brain tissue oxygenation derangement correlates with increasing cerebrovascular dysautoregulation in patients succumbing to severe head injury, supporting the utility of PRx as a monitoring variable and the rationale for a target-driven approach to head injury management.
authors.affiliation: Acute Brain Injury Research Laboratory, Department of Neurosurgery, National Neuroscience Institute, 11, Jalan Tan Tock Seng, Singapore 308433, Singapore.
authors.forename: B T
authors.initials: BT
authors.lastname: Ang
authors.forename: J
authors.initials: J
authors.lastname: Wong
authors.forename: K K
authors.initials: KK
authors.lastname: Lee
authors.forename: E
authors.initials: E
authors.lastname: Wang
authors.forename: I
authors.initials: I
authors.lastname: Ng
mesh_terms: D000328:Adult; D001921:Brain / Q000378:metabolism*; D001930:Brain Injuries / Q000401:mortality / Q000503:physiopathology*; D002545:Brain Ischemia; D016022:Case-Control Studies; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007427:Intracranial Pressure; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000378:metabolism*; D011446:Prospective Studies; D012039:Regional Blood Flow; D012720:Severity of Illness Index; D013997:Time Factors
chemical_list: D010100:Oxygen