title: Forbidden word entropy of cerebral oximetric values predicts postoperative neurocognitive decline in patients undergoing aortic arch surgery under deep hypothermic circulatory arrest.
abstract: OBJECTIVE
  Up to 53% of cardiac surgery patients experience postoperative neurocognitive decline. Cerebral oximetry is designed to detect changes in cerebral tissue saturation and therefore may be useful to predict which patients are at risk of developing neurocognitive decline.
  
  
  METHODS
  This is a retrospective analysis of a prospective study originally designed to determine if treatment of cerebral oximetry desaturation is associated with improvement in postoperative cognitive dysfunction in patients undergoing aortic reconstruction under deep hypothermic circulatory arrest. Cognitive function was measured, preoperatively and 3 months postoperatively, with 15 neuropsychologic tests administered by a psychologist; the individual test scores were summed and normalized. Bilateral cerebral oximetry data were stored and analyzed using measures of entropy. Cognitive decline was defined as any decrease in the summed normalized score from baseline to 3 months.
  
  
  RESULTS
  Seven of 17 (41%) patients suffered cognitive decline. There was no association between baseline cerebral oximetry and postoperative cognitive dysfunction. Nor were changes in oximetry values associated with cognitive decline. However, cognitive decline was associated with loss of forbidden word entropy (FwEn) (correlation: Rho ρ = 0.51, P = 0.037 for left cerebral oximetry FwEn and ρ = 0.54, P = 0.025 for right cerebral oximetry FwEn).
  
  
  CONCLUSIONS
  Postoperative cognitive decline was associated with loss of complexity of the time series as shown by a decrease in FwEn from beginning to end of the case. This suggests that regulation of cerebral oximetry is different between those who do and those who do not develop cognitive decline.
authors.affiliation: Department of Anesthesiology, University of Michigan, Ann Arbor, USA.
authors.forename: Anna
authors.initials: A
authors.lastname: Dubovoy
authors.affiliation: Department of Anesthesiology, Kaiser Permanente Health System, The Permanente Medical Group, Sacramento, CA, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Chang
authors.affiliation: Department of Psychology, University of Michigan, Ann Arbor, USA.
authors.forename: Carol
authors.initials: C
authors.lastname: Persad
authors.affiliation: Department of Anesthesiology, William Beaumont Health Systems, Royal Oak, MI, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Lau
authors.affiliation: Department of Anesthesiology, University of Michigan, Ann Arbor, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Jewell
authors.affiliation: Department of Physician Assistant Studies, Pace University, New York, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Cox
authors.affiliation: Department of Anesthesiology, University of Michigan, Ann Arbor, USA.
authors.forename: Milo
authors.initials: M
authors.lastname: Engoren
mesh_terms: D000368:Aged; D001013:Aorta, Thoracic / Q000601:surgery*; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D002560:Cerebrovascular Circulation / Q000502:physiology; D050792:Circulatory Arrest, Deep Hypothermia Induced; D003072:Cognition Disorders / Q000175:diagnosis*; D019277:Entropy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D010092:Oximetry / Q000706:statistics & numerical data*; D011183:Postoperative Complications / Q000175:diagnosis* / Q000209:etiology; D011237:Predictive Value of Tests; D011300:Preoperative Care / Q000379:methods; D011446:Prospective Studies; D012189:Retrospective Studies