title: Evaluation of a cerebral oximeter as a monitor of cerebral ischemia during carotid endarterectomy.
abstract: BACKGROUND
  Stroke is an important contributor to perioperative morbidity and mortality associated with carotid endarterectomy (CEA). This investigation was designed to compare the performance of the INVOS-3100 cerebral oximeter to neurologic function, as a means of detecting cerebral ischemia induced by carotid cross-clamping, in patients undergoing carotid endarterectomy with cervical plexus block.
  
  
  METHODS
  Ninety-nine patients undergoing 100 CEAs with regional anesthesia (deep or superficial cervical plexus block) were studied. Bilateral regional cerebrovascular oxygen saturation (rSO2) was monitored using the INVOS-3100 cerebral oximeter. Patients were retrospectively assigned to one of two groups: those in whom a change in mental status or contralateral motor deficit was noted after internal carotid clamping (neurologic symptoms; n = 10) and those who did not show any neurologic change (no neurologic symptoms; n = 90). Data from 94 operations (neurologic symptoms = 10 and no neurologic symptoms = 84) were adequate for statistical analyses for group comparisons. A relative decrease in ipsilateral rSO2 after carotid occlusion (calculated as a percentage of preocclusion value) during all operations (n = 100) was also calculated to determine the critical level of rSO2 decrease associated with a change in neurologic function.
  
  
  RESULTS
  The mean (+/- SD) decrease in rSO2 after carotid occlusion in the neurologic symptoms group (from 63.2 +/- 8.4% to 51.0 +/- 11.6%) was significantly greater (P = 0.0002) than in the no neurologic symptoms group (from 65.8 +/- 8.5% to 61.0 +/- 9.3%). Logistic regression analysis used to determine if a change in rSO2, calculated as a percentage of preclamp value, could be used to predict change in neurologic function was highly significant (likelihood ratio chi-square = 13.7; P = 0.0002). A 20% decrease in rSO2 reading from the preclamp baseline, as a predictor of neurologic compromise, resulted in a sensitivity of 80% and specificity of 82.2%. The false-positive rate using this cutoff point was 66.7%, and the false-negative rate was 2.6%, providing a positive predictive value of 33.3% and a negative predictive value of 97.4%.
  
  
  CONCLUSIONS
  Monitoring rSO2 with INVOS-3100 to detect cerebral ischemia during CEA has a high negative predictive value, but the positive predictive value is low.
authors.affiliation: Departments of Anesthesiology and Surgery, University of Michigan Health System, Ann Arbor, Michigan, USA. satsam@umich.edu
authors.forename: S K
authors.initials: SK
authors.lastname: Samra
authors.forename: E A
authors.initials: EA
authors.lastname: Dy
authors.forename: K
authors.initials: K
authors.lastname: Welch
authors.forename: P
authors.initials: P
authors.lastname: Dorje
authors.forename: G B
authors.initials: GB
authors.lastname: Zelenock
authors.forename: J C
authors.initials: JC
authors.lastname: Stanley
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000098:blood supply / Q000502:physiology; D002545:Brain Ischemia / Q000097:blood / Q000175:diagnosis* / Q000209:etiology; D002560:Cerebrovascular Circulation; D002572:Cervical Plexus; D016894:Endarterectomy, Carotid / Q000009:adverse effects* / Q000379:methods; D005260:Female; D006801:Humans; D007431:Intraoperative Complications / Q000097:blood / Q000175:diagnosis / Q000209:etiology; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D009407:Nerve Block; D010092:Oximetry / Q000295:instrumentation / Q000379:methods; D010100:Oxygen / Q000097:blood; D012189:Retrospective Studies; D019265:Spectroscopy, Near-Infrared / Q000379:methods
chemical_list: D010100:Oxygen