title: Continuous monitoring of cerebrovascular reactivity using pulse waveform of intracranial pressure.
abstract: BACKGROUND
  Guidelines for the management of traumatic brain injury (TBI) call for the development of accurate methods for assessment of the relationship between cerebral perfusion pressure (CPP) and cerebral autoregulation and to determine the influence of quantitative indices of pressure autoregulation on outcome. We investigated the relationship between slow fluctuations of arterial blood pressure (ABP) and intracranial pressure (ICP) pulse amplitude (an index called PAx) using a moving correlation technique to reflect the state of cerebral vasoreactivity and compared it to the index of pressure reactivity (PRx) as a moving correlation coefficient between averaged values of ABP and ICP.
  
  
  METHODS
  A retrospective analysis of prospective 327 TBI patients (admitted on neurocritical care unit of a university hospital in the period 2003-2009) with continuous ABP and ICP monitoring.
  
  
  RESULTS
  PAx was worse in patients who died compared to those who survived (-0.04 ± 0.15 vs. -0.16 ± 0.15, χ2 = 28, p < 0.001). In contrast to PRx, PAx was able to differentiate between fatal and non-fatal outcome in a group of 120 patients with ICP levels below 15 mmHg (-0.04 ± 0.16 vs. -0.14 ± 0.16, χ2 = 6, p = 0.01).
  
  
  CONCLUSIONS
  PAx is a new modified index of cerebrovascular reactivity which performs equally well as established PRx in long-term monitoring in severe TBI patients, but importantly is potentially more robust at lower values of ICP. In view of establishing an autoregulation-oriented CPP therapy, continuous determination of PAx is feasible but its value has to be evaluated in a prospective controlled trail.
authors.affiliation: Academic Neurosurgery Unit, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK. m.j.h.aries@umcg.nl
authors.forename: Marcel J H
authors.initials: MJ
authors.lastname: Aries
authors.forename: Marek
authors.initials: M
authors.lastname: Czosnyka
authors.forename: Karol P
authors.initials: KP
authors.lastname: Budohoski
authors.forename: Angelos G
authors.initials: AG
authors.lastname: Kolias
authors.forename: Danila K
authors.initials: DK
authors.lastname: Radolovich
authors.forename: Andrea
authors.initials: A
authors.lastname: Lavinio
authors.forename: John D
authors.initials: JD
authors.lastname: Pickard
authors.forename: Peter
authors.initials: P
authors.lastname: Smielewski
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001930:Brain Injuries / Q000175:diagnosis* / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003422:Critical Care / Q000379:methods; D016208:Databases, Factual; D005260:Female; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods*; D011673:Pulsatile Flow / Q000502:physiology*; D012189:Retrospective Studies; D016896:Treatment Outcome; D055815:Young Adult