title: Low intraoperative tidal volume ventilation with minimal PEEP is associated with increased mortality.
abstract: BACKGROUND
  Anaesthetists have traditionally ventilated patients' lungs with tidal volumes (TVs) between 10 and 15 ml kg(-1) of ideal body weight (IBW), without the use of PEEP. Over the past decade, influenced by the results of the Acute Respiratory Distress Syndrome Network trial, many anaesthetists have begun using lower TVs during surgery. It is unclear whether the benefits of low TV ventilation can be extended into the perioperative period.
  
  
  METHODS
  We reviewed the records of 29 343 patients who underwent general anaesthesia with mechanical ventilation between January 1, 2008 and December 31, 2011. We calculated TV kg(-1) IBW, PEEP, peak inspiratory pressure (PIP), and dynamic compliance. Cox regression analysis with propensity score matching was performed to examine the association between TV and 30-day mortality.
  
  
  RESULTS
  Median TV was 8.6 [7.7-9.6] ml kg(-1) IBW with minimal PEEP [4.0 (2.2-5.0) cm H2O]. A significant reduction in TV occurred over the study period, from 9 ml kg(-1) IBW in 2008 to 8.3 ml kg(-1) IBW in 2011 (P=0.01). Low TV 6-8 ml kg(-1) IBW was associated with a significant increase in 30-day mortality vs TV 8-10 ml kg(-1) IBW: hazard ratio (HR) 1.6 [95% confidence interval (CI) [1.25-2.08], P=0.0002]. The association remained significant after matching: HR 1.63 [95% CI (1.22-2.18), P<0.001]. There was only a weak correlation between TV kg(-1) IBW and dynamic compliance (r=-0.006, P=0.31) and a weak-to-moderate correlation between TV kg(-1) IBW and PIP (r=0.32 P<0.0001).
  
  
  CONCLUSIONS
  Use of low intraoperative TV with minimal PEEP is associated with an increased risk of 30-day mortality.
authors.affiliation: Department of Anesthesiology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1010, New York, NY 10029, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Levin
authors.affiliation: Department of Anesthesiology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1010, New York, NY 10029, USA.
authors.forename: P J
authors.initials: PJ
authors.lastname: McCormick
authors.affiliation: Department of Anesthesiology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1010, New York, NY 10029, USA Department of Health Evidence and Policy, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1010, New York, NY 10029, USA.
authors.forename: H M
authors.initials: HM
authors.lastname: Lin
authors.affiliation: Department of Anesthesiology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1010, New York, NY 10029, USA.
authors.forename: L
authors.initials: L
authors.lastname: Hosseinian
authors.affiliation: Department of Anesthesiology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1010, New York, NY 10029, USA Department of Cardiothoracic Surgery, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1010, New York, NY 10029, USA gregory.fischer@mountsinai.org.
authors.forename: G W
authors.initials: GW
authors.lastname: Fischer
mesh_terms: D000328:Adult; D000368:Aged; D000768:Anesthesia, General / Q000379:methods; D005260:Female; D006801:Humans; D007430:Intraoperative Care / Q000379:methods*; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D009519:New York City / Q000453:epidemiology; D011175:Positive-Pressure Respiration / Q000009:adverse effects / Q000379:methods*; D012189:Retrospective Studies; D018570:Risk Assessment / Q000379:methods; D013514:Surgical Procedures, Operative / Q000401:mortality; D013990:Tidal Volume / Q000502:physiology*
keywords: intraoperative care; pulmonary ventilation; tidal volume