title: Intraoperative ventilator settings and acute lung injury after elective surgery: a nested case control study.
abstract: BACKGROUND
  While acute lung injury (ALI) is among the most serious postoperative pulmonary complications, its incidence, risk factors and outcome have not been prospectively studied.
  
  
  OBJECTIVE
  To determine the incidence and survival of ALI associated postoperative respiratory failure and its association with intraoperative ventilator settings, specifically tidal volume.
  
  
  METHODS
  Prospective, nested, case control study.
  
  
  METHODS
  Single tertiary referral centre.
  
  
  METHODS
  4420 consecutive patients without ALI undergoing high risk elective surgeries for postoperative pulmonary complications.
  
  
  METHODS
  Incidence of ALI, survival and 2:1 matched case control comparison of intraoperative exposures.
  
  
  RESULTS
  238 (5.4%) patients developed postoperative respiratory failure. Causes included ALI in 83 (35%), hydrostatic pulmonary oedema in 74 (31%), shock in 27 (11.3%), pneumonia in nine (4%), carbon dioxide retention in eight (3.4%) and miscellaneous in 37 (15%). Compared with match controls (n = 166), ALI cases had lower 60 day and 1 year survival (99% vs 73% and 92% vs 56%; p<0.001). Cases were more likely to have a history of smoking, chronic obstructive pulmonary disease and diabetes, and to be exposed to longer duration of surgery, intraoperative hypotension and larger amount of fluid and transfusions. After adjustment for non-ventilator parameters, mean first hour peak airway pressure (OR 1.07; 95% CI 1.02 to 1.15 cm H(2)O) but not tidal volume (OR 1.03; 95% CI 0.84 to 1.26 ml/kg), positive end expiratory pressure (OR 0.89; 95% CI 0.77 to 1.04 cm H(2)O) or fraction of inspired oxygen (OR 1.0; 95% CI 0.98 to 1.03) were associated with ALI.
  
  
  CONCLUSIONS
  ALI is the most common cause of postoperative respiratory failure and is associated with markedly lower postoperative survival. Intraoperative tidal volume was not associated with an increased risk for early postoperative ALI.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, National Jewish Health, 1400 Jackson Street, G10a, Denver, CO 80206, USA. FernandezEvans@njc.org
authors.forename: E R
authors.initials: ER
authors.lastname: Fernández-Pérez
authors.forename: J
authors.initials: J
authors.lastname: Sprung
authors.forename: B
authors.initials: B
authors.lastname: Afessa
authors.forename: D O
authors.initials: DO
authors.lastname: Warner
authors.forename: C M
authors.initials: CM
authors.lastname: Vachon
authors.forename: D R
authors.initials: DR
authors.lastname: Schroeder
authors.forename: D R
authors.initials: DR
authors.lastname: Brown
authors.forename: R D
authors.initials: RD
authors.lastname: Hubmayr
authors.forename: O
authors.initials: O
authors.lastname: Gajic
mesh_terms: D055371:Acute Lung Injury / Q000517:prevention & control*; D000704:Analysis of Variance; D016022:Case-Control Studies; D017558:Elective Surgical Procedures; D017052:Hospital Mortality; D006801:Humans; D007430:Intraoperative Care / Q000295:instrumentation; D011183:Postoperative Complications / Q000517:prevention & control*; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000295:instrumentation*; D012131:Respiratory Insufficiency / Q000517:prevention & control; D016019:Survival Analysis; D012122:Ventilators, Mechanical