title: Asymmetry of cerebral autoregulation following head injury.
abstract: OBJECTIVE
  To investigate asymmetry of cerebra autoregulation in head-injured patients with lateral brain contusions.
  
  
  METHODS
  Sixty five patients were admitted to Addenbrooke's Hospital suffering from head injuries with mean Glasgow Coma Score 6 (range 3 to 10). The patients were paralyzed, sedated and ventilated to achieve mild hypocapnia. Intracranial pressure (ICP), arterial pressure (ABP) were monitored directly. The left and right Middle Cerebral Arteries were insonated daily and flow velocity (FV) was recorded. Correlation coefficients between slow waves in cerebral perfusion pressure (CPP) and FV were calculated for every 3 minute period. Positive value of Mx denotes a positive association between waves in FV and CPP, therefore deranged autoregulation. Zero or slightly negative value of Mx denotes a good autoregulatory capacity. In each patient all CT scans were reviewed to assess a dominant side of brain contusion and a level of brain compression.
  
  
  RESULTS
  The side-to-side difference in FV, pulsatility indices or critical closing pressures, did not correlate with the side of contusion or midline shift. In contrary, the side-to-side difference in Mx indices were significantly (p < 0.05) worse at a side of contusion and at the side of brain expansion in patients presenting with a midline shift (p < 0.05). Of those patients who died in hospital, significantly more presented within meaningful (ABS(Mx) > 0.2) asymmetry in cerebral autoregulation (40% versus 12%; p < 0.05).
  
  
  CONCLUSIONS
  Side-to-side difference in cerebral hemodynamic reserve of injured brain is a predictor of fatal outcome following head injury and correlates with the side of contusion or brain expansion.
authors.affiliation: Academic Neurosurgical Unit, Addenbrooke's Hospital, Wolfson Brain Imaging Centre, University of Cambridge, UK.
authors.forename: E A
authors.initials: EA
authors.lastname: Schmidt
authors.forename: M
authors.initials: M
authors.lastname: Czosnyka
authors.forename: P
authors.initials: P
authors.lastname: Smielewski
authors.forename: S K
authors.initials: SK
authors.lastname: Piechnik
authors.forename: J D
authors.initials: JD
authors.lastname: Pickard
mesh_terms: D001783:Blood Flow Velocity; D001794:Blood Pressure / Q000502:physiology*; D002245:Carbon Dioxide / Q000097:blood; D002560:Cerebrovascular Circulation / Q000502:physiology*; D006259:Craniocerebral Trauma / Q000000981:diagnostic imaging / Q000503:physiopathology*; D007839:Functional Laterality; D015600:Glasgow Coma Scale; D006706:Homeostasis; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology*; D020768:Middle Cerebral Artery / Q000503:physiopathology; D008991:Monitoring, Physiologic / Q000379:methods; D017585:Ultrasonography, Doppler, Transcranial
chemical_list: D002245:Carbon Dioxide