title: Brain tissue oxygen, carbon dioxide, and pH in neurosurgical patients at risk for ischemia.
abstract: A sensor that measures oxygen pressure (PO2), carbon dioxide pressure (PCO2), and pH was evaluated in brain tissue of patients at risk for ischemia. The sensor is 0.5 mm in diameter and was inserted into cortex tissue in 14 patients undergoing craniotomy for cerebrovascular surgery. A compromised cerebral circulation was identified in 8 of 14 patients by single photon emission computed tomography (SPECT) scan, cerebral angiography, and transient ischemic episodes before surgery. Under baseline conditions with isoflurane anesthesia and normal blood gases, tissue P02 was lower in the eight compromised compared to six noncompromised patients (noncompromised 37 +/- 12 mm Hg, compromised 10 +/- 5 mm Hg; P < 0.05), PCO2 was increased (noncompromised 49 +/- 5 mm Hg, compromised 72 +/- 23 mm Hg; P < 0.05), and pH was decreased (noncompromised 7.16 +/- 0.08, compromised 6.82 +/- 0.21; P < 0.05). Critical tissue values for the identification of ischemia were a P02 of 20 mm Hg, PCO2 of 60 mm Hg, and a pH of 7.0. These results suggest that brain tissue measures of P02, PCO2, and pH provide information on the adequacy of cerebral perfusion in neurosurgical patients.
authors.affiliation: Department of Anesthesiology, University of Illinois, Chicago 60612, 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
mesh_terms: D000328:Adult; D000769:Anesthesia, Inhalation; D018685:Anesthetics, Inhalation / Q000008:administration & dosage; D001784:Blood Gas Analysis; D001921:Brain / Q000378:metabolism*; D002545:Brain Ischemia / Q000209:etiology* / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism*; D002533:Cerebral Angiography; D002540:Cerebral Cortex / Q000378:metabolism; D002560:Cerebrovascular Circulation; D002561:Cerebrovascular Disorders / Q000378:metabolism / Q000601:surgery*; D003399:Craniotomy; D004867:Equipment Design; D006801:Humans; D006863:Hydrogen-Ion Concentration; D002546:Ischemic Attack, Transient / Q000209:etiology / Q000378:metabolism; D007530:Isoflurane / Q000008:administration & dosage; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption; D010313:Partial Pressure; D012307:Risk Factors; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D018685:Anesthetics, Inhalation; D002245:Carbon Dioxide; D007530:Isoflurane; D010100:Oxygen