title: Apneic Oxygenation Versus Low-Tidal-Volume Ventilation in Anesthetized Cardiac Surgical Patients: A Prospective, Single-Center, Randomized Controlled Trial.
abstract: OBJECTIVE
  To compare the physiology of apneic oxygenation with low-tidal-volume (VT) ventilation during harvesting of the left internal mammary artery.
  
  
  METHODS
  Prospective, single-center, randomized trial.
  
  
  METHODS
  Single-center teaching hospital.
  
  
  METHODS
  The study comprised 24 patients who underwent elective coronary artery bypass grafting surgery.
  
  
  METHODS
  Apneic oxygenation (apneic group: 12 participants) and low-VT ventilation (low-VT group: 12 participants) (2.5 mL/kg ideal body weight) for 15 minutes during harvesting of the left internal mammary artery.
  
  
  RESULTS
  The primary endpoint was an absolute change in partial pressure of arterial carbon dioxide (PaCO2). Secondary endpoints were changes in arterial pH, pulmonary artery pressures (PAP), cardiac index, and pulmonary artery acceleration time and ease of surgical access. The mean (standard deviation) absolute increase in PaCO2was 31.8 mmHg (7.6) in the apneic group and 17.6 mmHg (8.2) in the low-VT group (baseline-adjusted difference 14.2 mmHg [95% confidence interval 21.0-7.3], p<0.001). The mean (standard deviation) absolute decrease in pH was 0.15 (0.03) in the apneic group and 0.09 (0.03) in the low-VT group baseline-adjusted difference 0.06 [95% confidence interval 0.03-0.09], p<0.001. Differences in the rate of change over time between groups (time-by-treatment interaction) were observed for PaCO2(p<0.001), pH (p<0.001), systolic PAP (p = 0.002), diastolic PAP (p = 0.023), and mean PAP (p = 0.034). Both techniques provided adequate ease of surgical access; however, apneic oxygenation was preferred predominantly.
  
  
  CONCLUSIONS
  Apneic oxygenation caused a greater degree of hypercarbia and respiratory acidemia compared with low-VT ventilation. Neither technique had deleterious effects on PAP or cardiac function. Both techniques provided adequate ease of surgical access.
authors.affiliation: University of Melbourne, Victoria, Australia.
authors.forename: Laura
authors.initials: L
authors.lastname: Machan
authors.affiliation: Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia.
authors.forename: Leonid
authors.initials: L
authors.lastname: Churilov
authors.affiliation: Department of Anesthesia, Austin Hospital, Heidelberg, Victoria, Australia.
authors.forename: Raymond
authors.initials: R
authors.lastname: Hu
authors.affiliation: Department of Anesthesia, Austin Hospital, Heidelberg, Victoria, Australia.
authors.forename: Philip
authors.initials: P
authors.lastname: Peyton
authors.affiliation: Department of Anesthesia, Austin Hospital, Heidelberg, Victoria, Australia.
authors.forename: Chong
authors.initials: C
authors.lastname: Tan
authors.affiliation: Department of Anesthesia, Austin Hospital, Heidelberg, Victoria, Australia.
authors.forename: Param
authors.initials: P
authors.lastname: Pillai
authors.affiliation: Department of Anesthesia, Austin Hospital, Heidelberg, Victoria, Australia.
authors.forename: Louise
authors.initials: L
authors.lastname: Ellard
authors.affiliation: Department of Anesthesia, Austin Hospital, Heidelberg, Victoria, Australia.
authors.forename: Ian
authors.initials: I
authors.lastname: Harley
authors.affiliation: Department of Anesthesia, University of Melbourne, Victoria, Australia; Department of Surgery and Centre for Anesthesia, Perioperative and Pain Medicine, University of Melbourne, Victoria, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Story
authors.affiliation: Department of Cardiac Surgery, Austin Hospital, Heidelberg, Victoria, Australia.
authors.forename: Philip
authors.initials: P
authors.lastname: Hayward
authors.affiliation: Department of Cardiac Surgery, Austin Hospital, Heidelberg, Victoria, Australia.
authors.forename: George
authors.initials: G
authors.lastname: Matalanis
authors.affiliation: Department of Cardiac Surgery, Austin Hospital, Heidelberg, Victoria, Australia.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Roubos
authors.affiliation: Department of Cardiac Surgery, Austin Hospital, Heidelberg, Victoria, Australia.
authors.forename: Sivendran
authors.initials: S
authors.lastname: Seevanayagam
authors.affiliation: Department of Anesthesia, University of Melbourne, Victoria, Australia; Department of Surgery and Centre for Anesthesia, Perioperative and Pain Medicine, University of Melbourne, Victoria, Australia. Electronic address: laurence.weinberg@austin.org.au.
authors.forename: Laurence
authors.initials: L
authors.lastname: Weinberg
mesh_terms: D000368:Aged; D006348:Cardiac Surgical Procedures / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008323:Mammary Arteries / Q000601:surgery; D008875:Middle Aged; D010102:Oxygen Inhalation Therapy / Q000379:methods*; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000379:methods*; D013990:Tidal Volume / Q000502:physiology*
keywords: apneic oxygenation; cardiac function; cardiac surgery; hypercarbia; low-tidal-volume ventilation; pulmonary artery pressures; respiratory acidemia