title: Concept of "true ICP" in monitoring and prognostication in head trauma.
abstract: OBJECTIVE
  To propose a new coefficient, which contains information about both the absolute ICP and the position of the 'working point' on the pressure-volume curve.
  
  
  METHODS
  ICP was monitored continuously in 187 sedated and ventilated patients. The RAP coefficient was calculated as the running (3 minutes) correlation coefficient between slow changes in pulse amplitude and mean ICP. RAP has value 0 on the flat part of the Pressure-Volume Curve and +1 on the ascending exponential part. Then RAP decreases to zero or becomes negative when ICP increases further and affects cerebrovascular pressure-reactivity (which flattens the pressure-volume curve). Variable tICP = ICP* (1 - RAP) has been called 'trueICP'. It magnifies the critical values of ICP when cerebrovascular reactivity is exhausted and dampens those states where absolute ICP is elevated but vascular reactivity is not affected.
  
  
  RESULTS
  Both Mean ICP and RAP were independently correlated with outcome (ANOVA:ICP-GOS: F = 22; p < 0.00001, RAP-GOS: F = 9; p < 0.001). 'TrueICP' had stronger association with outcome: F = 28; p < 0.000001. Mortality in those patients having 'trueICP' above the threshold of 19 mm Hg was above 80%, while the mortality in those having cICP below 19 mm Hg was only 20% (F = 80; p < 10(-8)). 'TrueICP' was also suitable for continuous monitoring: sustained rise in tICP above 19 mm Hg was strongly associated with fatal complications.
  
  
  CONCLUSIONS
  The proposed variable is a powerful predictor of fatal outcome following head injury. It is sensitive to both the rising absolute ICP and the critical loss of cerebrovascular regulation.
authors.affiliation: Academic Neurosurgical Unit, Addenbrooke's Hospital, Cambridge, UK. MC141@medschl.cam.ac.uk
authors.forename: M
authors.initials: M
authors.lastname: Czosnyka
authors.forename: L
authors.initials: L
authors.lastname: Steiner
authors.forename: M
authors.initials: M
authors.lastname: Balestreri
authors.forename: E
authors.initials: E
authors.lastname: Schmidt
authors.forename: P
authors.initials: P
authors.lastname: Smielewski
authors.forename: P J
authors.initials: PJ
authors.lastname: Hutchinson
authors.forename: J D
authors.initials: JD
authors.lastname: Pickard
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D006259:Craniocerebral Trauma / Q000175:diagnosis* / Q000503:physiopathology*; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D005260:Female; D006801:Humans; D007427:Intracranial Pressure; D008297:Male; D008365:Manometry / Q000379:methods*; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods*; D017063:Outcome Assessment, Health Care / Q000379:methods; D011379:Prognosis; D015203:Reproducibility of Results; D018570:Risk Assessment / Q000379:methods; D012307:Risk Factors; D012680:Sensitivity and Specificity; D015599:Trauma Severity Indices