title: Brain tissue gases and pH during arteriovenous malformation resection.
abstract: OBJECTIVE
  The purpose of this study was to determine whether baseline partial pressure of oxygen (PO2), partial carbon dioxide pressure (PCO2), and pH in brain tissue adjacent to arteriovenous malformations (AVMs) are different from those in control patients. In addition, PO2, PCO2, and pH changes were measured during resection of the AVMs.
  
  
  METHODS
  Two groups were studied. Group 1 (n = 8) was composed of nonischemic patients scheduled for cerebral aneurysm clipping. Group 2 (n = 13) was composed of patients undergoing neurosurgery for resection of AVMs. After the craniotomy, the dura was retracted and a combined PO2, PCO2, and pH sensor was inserted into nonischemic brain tissue in Group 1. In Group 2, the sensor was inserted into tissue 2 to 3 cm from the margin of the AVMs, within the same arterial blood supply. After equilibration of the sensor, tissue gases and pH were measured during steady-state anesthetic conditions in Group 1 and during resection of AVMs in Group 2.
  
  
  RESULTS
  Under baseline conditions before the start of surgery, tissue PO2 was decreased in patients with AVMs compared with control patients, but PCO2 and pH were not changed. During resection of the AVMs, PO2 and pH increased and PCO2 decreased compared with baseline measurements. These parameters did not change in control patients during a similar time period.
  
  
  CONCLUSIONS
  The results suggest that cerebrovascular or metabolic adaptation occurs in patients with AVMs with decreased tissue perfusion pressure as an adjustment for decreased oxygen delivery. During resection of AVMs, this adaptation produces a relative hyperemic environment with tissue hyperoxia, hypocapnia, and alkalosis that is not corrected by the end of surgery.
authors.affiliation: Department of Anesthesiology, University of Illinois at Chicago, USA.
authors.forename: W E
authors.initials: WE
authors.lastname: Hoffman
authors.forename: F T
authors.initials: FT
authors.lastname: Charbel
authors.forename: G
authors.initials: G
authors.lastname: Edelman
authors.forename: J I
authors.initials: JI
authors.lastname: Ausman
mesh_terms: D000136:Acid-Base Equilibrium / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D001165:Arteriovenous Malformations / Q000503:physiopathology / Q000601:surgery*; D002245:Carbon Dioxide / Q000097:blood*; D002540:Cerebral Cortex / Q000098:blood supply*; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000295:instrumentation*; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000502:physiology; D012039:Regional Blood Flow / Q000502:physiology; D015427:Reperfusion Injury / Q000503:physiopathology; D012307:Risk Factors
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen