title: Comparison of the effect of etomidate and desflurane on brain tissue gases and pH during prolonged middle cerebral artery occlusion.
abstract: BACKGROUND
  The authors compared the effects of etomidate and desflurane on brain tissue oxygen pressure (PO2), carbon dioxide pressure (PCO2), and pH in patients who had middle cerebral artery occlusion for > 15 min.
  
  
  METHODS
  After a craniotomy, a probe that measures PO2, PCO2, and pH was inserted into cortical tissue at risk for ischemia during middle cerebral artery occlusion. A burst suppression pattern of the electroencephalogram was induced with etomidate (n = 6) or 9% end-tidal desflurane (n = 6) started before middle cerebral artery occlusion. Mean blood pressure was supported with phenylephrine to 90-95 mmHg.
  
  
  RESULTS
  During baseline conditions, tissue PO2, PCO2, and pH were similar between the two groups (PO2 = 15 mmHg, PCO2 = 60 mmHg, pH = 7.1). During administration of etomidate before middle cerebral artery occlusion, tissue PO2 decreased in five of six patients without a change in PCO2 or pH. During administration of 9% desflurane, tissue PO2 and pH increased before middle cerebral artery clipping. Middle cerebral artery occlusion for an average of 33 min with etomidate and 37 min with desflurane produced a decrease in pH with etomidate (7.09 to 6.63, P < 0.05) but not with desflurane (7.12 to 7.15).
  
  
  CONCLUSIONS
  These results suggest that tissue hypoxia and acidosis are often observed during etomidate treatment and middle cerebral artery occlusion. Treatment with desflurane significantly increases tissue PO2 alone and attenuates acidotic changes to prolonged middle cerebral artery occlusion.
authors.affiliation: Department of Anesthesiology, University of Illinois at Chicago, USA. Whoffman@uic.edu
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: M
authors.initials: M
authors.lastname: Misra
authors.forename: J I
authors.initials: JI
authors.lastname: Ausman
mesh_terms: D000328:Adult; D000368:Aged; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D001921:Brain / Q000098:blood supply / Q000187:drug effects* / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D002536:Cerebral Arteries; D003250:Constriction; D000077335:Desflurane; D005045:Etomidate / Q000494:pharmacology*; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000378:metabolism; D007530:Isoflurane / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption
chemical_list: D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D002245:Carbon Dioxide; D000077335:Desflurane; D007530:Isoflurane; D005045:Etomidate