title: Measurement of brain tissue oxygenation performed using positron emission tomography scanning to validate a novel monitoring method.
abstract: OBJECTIVE
  The benefits of measuring cerebral oxygenation in patients with brain injury are well accepted; however, jugular bulb oximetry, which is currently the most popular monitoring technique used has several shortcomings. The goal of this study was to validate the use of a new multiparameter sensor that measures brain tissue oxygenation and metabolism (Neurotrend) by comparing it with positron emission tomography (PET) scanning.
  
  
  METHODS
  A Neurotrend sensor was inserted into the frontal region of the brain in 19 patients admitted to the neurointensive care unit. After a period of stabilization, the patients were transferred to the PET scanner suite where C15O, 15O2, and H2(15)O PET scans were obtained to facilitate calculation of regional cerebral blood volume, O2 metabolism, blood flow, and O2 extraction fraction (OEF). Patients were given hyperventilation therapy to decrease arterial CO2 by approximately 1 kPa (7.5 mm Hg) and the same sequence of PET scans was repeated. For each scanning sequence, end-capillary O2 tension (PvO2) was calculated from the OEF and compared with the reading of brain tissue O2 pressure (PbO2) provided by the sensor. In three patients the sensor was inserted into areas of contusion and these patients were eliminated from the analysis. In the subset of 16 patients in whom the sensor was placed in healthy brain, no correlation was found between the absolute values of PbO2 and PvO2 (r = 0.2, p = 0.29); however a significant correlation was obtained between the change in PbO2 (deltaPbO2) and the change in PvO2 (deltaPvO2) produced by hyperventilation in a 20-mm region of interest around the sensor (p = 0.78, p = 0.0035).
  
  
  CONCLUSIONS
  The lack of correlation between the absolute values of PbO2 and PvO2 indicates that PbO2 cannot be used as a substitute for PvO2. Nevertheless, the positive correlation between deltaPbO2 and deltaPvO2 when the sensor had been inserted into healthy brain suggests that tissue PO2 monitoring may provide a useful tool to assess the effect of therapeutic interventions in brain injury.
authors.affiliation: Department of Anaesthesia, Addenbrooke's Hospital, Cambridge, United Kingdom. akg01@globalnet.co.uk
authors.forename: Arun K
authors.initials: AK
authors.lastname: Gupta
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Hutchinson
authors.forename: Tim
authors.initials: T
authors.lastname: Fryer
authors.forename: Pippa G
authors.initials: PG
authors.lastname: Al-Rawi
authors.forename: Dot A
authors.initials: DA
authors.lastname: Parry
authors.forename: Pawan S
authors.initials: PS
authors.lastname: Minhas
authors.forename: Rupert
authors.initials: R
authors.lastname: Kett-White
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Kirkpatrick
authors.forename: Julian C
authors.initials: JC
authors.lastname: Mathews
authors.forename: Steve
authors.initials: S
authors.lastname: Downey
authors.forename: Franklin
authors.initials: F
authors.lastname: Aigbirhio
authors.forename: John
authors.initials: J
authors.lastname: Clark
authors.forename: John D
authors.initials: JD
authors.lastname: Pickard
authors.forename: David K
authors.initials: DK
authors.lastname: Menon
mesh_terms: D000328:Adult; D001810:Blood Volume / Q000502:physiology; D001921:Brain / Q000000981:diagnostic imaging* / Q000378:metabolism* / Q000503:physiopathology; D001930:Brain Injuries / Q000000981:diagnostic imaging* / Q000378:metabolism* / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000502:physiology; D005260:Female; D006801:Humans; D006985:Hyperventilation / Q000000981:diagnostic imaging / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000295:instrumentation* / Q000379:methods*; D010092:Oximetry / Q000295:instrumentation* / Q000379:methods*; D010100:Oxygen / Q000032:analysis*; D012044:Regression Analysis; D012682:Sensory Aids; D014055:Tomography, Emission-Computed
chemical_list: D010100:Oxygen