title: Does off-pump surgery offer benefit in high respiratory risk patients? A respiratory risk stratified analysis in a propensity-matched cohort.
abstract: OBJECTIVE
  The role of off-pump surgery in high respiratory risk patients remains unclear. In this study, we aim to evaluate the effect of off-pump surgery on high respiratory risk patients.
  
  
  METHODS
  To achieve comparative groups, a five digit propensity score matching with 18 pre-operative variables was performed on 4406 consecutive CABG patients operated between January 2000 and September 2003. Respiratory risk stratification was performed with the following variables: (1) FEV(1)<65% of predicted, (2) patients>75 years old, (3) history of current smoking, (4) body mass index more than 40 kg/m(2) and (5) NYHA class IV dyspnoea in combination with current respiratory medication. The presence of two or more variables defined high risk. The primary end point was post-operative ventilation time. We also compared alveolar arterial gradients (A-a gradient) on admission to ITU, 2 and 4h using Friedman rank time analysis.
  
  
  RESULTS
  We matched 1353 off-pump patients with 1353 unique on-pump patients. Respiratory risk stratified selection resulted in 73 off-pump and 55 on-pump high-risk patients. In the off-pump group, four (5.5%) patients had more than two selection criteria, compared to one (1.8%) for on-pump patients (p=0.29). The off-pump group had more patients with FEV1<65% compared to on-pump: 65 (89.0%) versus 40 (72.7%); p=0.017. The median ventilation time was significantly shorter for off-pump patients (7h [IQR: 5-14] vs 12h [IQR: 7-18], p=0.003). In the off-pump group, three (4.1%) patients had a ventilation time>48 h compared to eight (14.6%) in the on-pump group, p=0.037. A-a gradient measurements on admission to ITU were lower in off-pump patients (median: 182.3 [IQR: 126.6-216.2]) compared to on-pump patients (median: 194.7 [IQR 139.7-245.4], p=0.064).
  
  
  CONCLUSIONS
  Off-pump surgery offers benefit to high respiratory risk patients by reducing post-operative ventilation time. Off-pump patients also have lower A-a gradients in the early post-operative period but this failed to reach significance.
authors.affiliation: Department of Cardiothoracic Surgery, The Cardiothoracic Centre-Liverpool, Thomas Drive, Liverpool L14 3PE, United Kingdom. reddylcs@aol.com
authors.forename: Shekar L C
authors.initials: SL
authors.lastname: Reddy
authors.forename: Antony D
authors.initials: AD
authors.lastname: Grayson
authors.forename: Aung Y
authors.initials: AY
authors.lastname: Oo
authors.forename: Mark D
authors.initials: MD
authors.lastname: Pullan
authors.forename: Thejaswi
authors.initials: T
authors.lastname: Poonacha
authors.forename: Brian M
authors.initials: BM
authors.lastname: Fabri
mesh_terms: D000368:Aged; D015992:Body Mass Index; D015331:Cohort Studies; D047549:Coronary Artery Bypass, Off-Pump / Q000009:adverse effects; D004417:Dyspnea / Q000150:complications; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D011182:Postoperative Care / Q000379:methods; D011183:Postoperative Complications / Q000517:prevention & control*; D012121:Respiration, Artificial; D012128:Respiratory Distress Syndrome / Q000517:prevention & control*; D018570:Risk Assessment; D012907:Smoking / Q000009:adverse effects