title: Effects of variation in cerebral haemodynamics during aneurysm surgery on brain tissue oxygen and metabolism.
abstract: OBJECTIVE
  This study explores the sensitivities of multiparameter tissue gas sensors and microdialysis to variations in blood pressure, CSF drainage and to well-defined periods of ischaemia accompanying aneurysm surgery, and their predictive value for infarction.
  
  
  METHODS
  A Neurotrend sensor [brain tissue partial pressure of oxygen (PBO2), carbon dioxide (PBCO2), brain pH (pHB) and temperature] and microdialysis catheter were inserted into the appropriate vascular territory prior to craniotomy.
  
  
  RESULTS
  Baseline data showed a clear correlation between PBO2 and mean arterial pressure (MAP) below a threshold of 80 mmHg. PBO2 improved with CSF drainage in 20 out of 28 (Wilcoxon: P < 0.05) cases where data was available. In 26 patients the effects of temporary vascular clipping (TC) (mean duration 16 minutes) were assessed. 2 patients subsequently declared infarction in the region of the probes. PBO2 fell from a mean 3.2 (95% CI 2.4-4.1) kPa to a minimum of 1.5 (95% CI 1.0-2.0) kPa in the non-infarct group. There was a lower baseline PBO2 (mean 0.8 kPa) in the patients who infarcted. PBCO2 mirrored PBO2 changes, whereas pHB did not change significantly in either group. Microdialysis changes associated with decreased PBO2 included a delayed increase in lactate, a raised lactate/pyruvate ratio and more rarely an increased glutamate. These changes were seen in 11 patients but were not predictive of infarction.
  
  
  CONCLUSIONS
  Hypotension during aneurysm surgery is associated with a low PBO2. Multiparameter sensors can be sensitive to acute ischaemia. Microdialysis shows potential in the detection of metabolic changes during tissue hypoxia.
authors.affiliation: Academic Department of Neurosurgery, Wolfson Brain Imaging Centre, Addenbrooke's Hospital, Cambridge, UK.
authors.forename: R
authors.initials: R
authors.lastname: Kett-White
authors.forename: P J
authors.initials: PJ
authors.lastname: Hutchinson
authors.forename: M
authors.initials: M
authors.lastname: Czosnyka
authors.forename: P
authors.initials: P
authors.lastname: al-Rawi
authors.forename: A
authors.initials: A
authors.lastname: Gupta
authors.forename: J D
authors.initials: JD
authors.lastname: Pickard
authors.forename: P J
authors.initials: PJ
authors.lastname: Kirkpatrick
mesh_terms: D000328:Adult; D000368:Aged; D001794:Blood Pressure; D002544:Cerebral Infarction / Q000209:etiology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003399:Craniotomy; D006439:Hemodynamics; D006801:Humans; D002532:Intracranial Aneurysm / Q000378:metabolism / Q000503:physiopathology / Q000601:surgery*; D007427:Intracranial Pressure / Q000502:physiology*; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000009:adverse effects / Q000379:methods; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D010313:Partial Pressure; D000091402:Prohibitins
chemical_list: C000717328:PHB protein, human; D000091402:Prohibitins; D010100:Oxygen