title: Continuous monitoring of cerebrovascular pressure reactivity allows determination of optimal cerebral perfusion pressure in patients with traumatic brain injury.
abstract: OBJECTIVE
  To define optimal cerebral perfusion pressure (CPPOPT) in individual head-injured patients using continuous monitoring of cerebrovascular pressure reactivity. To test the hypothesis that patients with poor outcome were managed at a cerebral perfusion pressure (CPP) differing more from their CPPOPT than were patients with good outcome.
  
  
  METHODS
  Retrospective analysis of prospectively collected data.
  
  
  METHODS
  Neurosciences critical care unit of a university hospital.
  
  
  METHODS
  A total of 114 head-injured patients admitted between January 1997 and August 2000 with continuous monitoring of mean arterial blood pressure (MAP) and intracranial pressure (ICP).
  
  
  RESULTS
  MAP, ICP, and CPP were continuously recorded and a pressure reactivity index (PRx) was calculated online. PRx is the moving correlation coefficient recorded over 4-min periods between averaged values (6-sec periods) of MAP and ICP representing cerebrovascular pressure reactivity. When cerebrovascular reactivity is intact, PRx has negative or zero values, otherwise PRx is positive. Outcome was assessed at 6 months using the Glasgow Outcome Scale. A total of 13,633 hrs of data were recorded. CPPOPT was defined as the CPP where PRx reaches its minimum value when plotted against CPP. Identification of CPPOPT was possible in 68 patients (60%). In 22 patients (27%), CPPOPT was not found because it presumably lay outside the studied range of CPP. Patients' outcome correlated with the difference between CPP and CPPOPT for patients who were managed on average below CPPOPT (r =.53, p <.001) and for patients whose mean CPP was above CPPOPT (r = -.40, p <.05).
  
  
  CONCLUSIONS
  CPPOPT could be identified in a majority of patients. Patients with a mean CPP close to CPPOPT were more likely to have a favorable outcome than those whose mean CPP was more different from CPPOPT. We propose use of the criterion of minimal achievable PRx to guide future trials of CPP oriented treatment in head injured patients.
authors.affiliation: Academic Neurosurgery, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom. las30@cam.ac.uk
authors.forename: Luzius A
authors.initials: LA
authors.lastname: Steiner
authors.forename: Marek
authors.initials: M
authors.lastname: Czosnyka
authors.forename: Stefan K
authors.initials: SK
authors.lastname: Piechnik
authors.forename: Piotr
authors.initials: P
authors.lastname: Smielewski
authors.forename: Doris
authors.initials: D
authors.lastname: Chatfield
authors.forename: David K
authors.initials: DK
authors.lastname: Menon
authors.forename: John D
authors.initials: JD
authors.lastname: Pickard
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001794:Blood Pressure / Q000502:physiology; D001930:Brain Injuries / Q000175:diagnosis* / Q000503:physiopathology; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic