title: Influence of Ventilation Strategies and Anesthetic Techniques on Regional Cerebral Oximetry in the Beach Chair Position: A Prospective Interventional Study with a Randomized Comparison of Two Anesthetics.
abstract: BACKGROUND
  Beach chair positioning during general anesthesia is associated with cerebral oxygen desaturation. Changes in cerebral oxygenation resulting from the interaction of inspired oxygen fraction (FIO2), end-tidal carbon dioxide (PETCO2), and anesthetic choice have not been fully evaluated in anesthetized patients in the beach chair position.
  
  
  METHODS
  This is a prospective interventional within-group study of patients undergoing shoulder surgery in the beach chair position that incorporated a randomized comparison between two anesthetics. Fifty-six patients were randomized to receive desflurane or total intravenous anesthesia with propofol. Following induction of anesthesia and positioning, FIO2 and minute ventilation were sequentially adjusted for all patients. Regional cerebral oxygenation (rSO2) was the primary outcome and was recorded at each of five set points.
  
  
  RESULTS
  While maintaining FIO2 at 0.3 and PETCO2 at 30 mmHg, there was a decrease in rSO2 from 68% (SD, 12) to 61% (SD, 12) (P < 0.001) following beach chair positioning. The combined interventions of increasing FIO2 to 1.0 and increasing PETCO2 to 45 mmHg resulted in a 14% point improvement in rSO2 to 75% (SD, 12) (P <0.001) for patients anesthetized in the beach chair position. There was no significant interaction effect of the anesthetic at the study intervention points.
  
  
  CONCLUSIONS
  Increasing FIO2 and PETCO2 resulted in a significant increase in rSO2 that overcomes desaturation in patients anesthetized in the beach chair position and that appears independent of anesthetic choice.
authors.affiliation: From the Department of Anesthesiology (P.P., A.D., A.A., M.N., A.S., M.H., G.A.M.) and Department of Orthopedic Surgery (B.S.M.), University of Michigan Medical School, Ann Arbor, Michigan.
authors.forename: Paul
authors.initials: P
authors.lastname: Picton
authors.forename: Andrew
authors.initials: A
authors.lastname: Dering
authors.forename: Amir
authors.initials: A
authors.lastname: Alexander
authors.forename: Mary
authors.initials: M
authors.lastname: Neff
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Miller
authors.forename: Amy
authors.initials: A
authors.lastname: Shanks
authors.forename: Michelle
authors.initials: M
authors.lastname: Housey
authors.forename: George A
authors.initials: GA
authors.lastname: Mashour
mesh_terms: D000777:Anesthetics / Q000008:administration & dosage*; D001182:Arthroscopy / Q000379:methods*; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010092:Oximetry / Q000379:methods*; D056888:Patient Positioning / Q000379:methods*; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000379:methods*; D012785:Shoulder Joint / Q000601:surgery
chemical_list: D000777:Anesthetics