The Effects of On-Pump and Off-Pump Coronary Artery Bypass Surgery on Respiratory Function in the Early Postoperative Period

Abstract

Background: Respiratory complications are common after cardiac surgery and the use of extracorporeal circulation is one of the main causes of lung injury. We hypothesized a better postoperative respiratory function in off-pump coronary artery bypass grafting (OPCABG) as compared with “on-pump coronary artery bypass grafting” (ONCABG). Methods: This is a retrospective, single-center study at a cardiothoracic intensive care unit (ICU) in a tertiary university hospital. Consecutive data on 339 patients undergoing elective CABG (n = 215 ONCABG, n = 124 OPCABG) were collected for 1 year from the ICU electronic medical records. We compared respiratory variables (Pao2, Pao2/Fio2 ratio, Sao2, and Paco2) at 7 predefined time points (ICU admission, postoperative hours 1, 3, 6, 12, 18, and 24). We also evaluated time to extubation, rates of reintubation, and use of noninvasive ventilation (NIV). We used mixed-effects linear regression models (with time as random effect for clustering of repeated measures) adjusted for a predetermined set of covariates. Results: The values of Pao2 and Pao2/Fio2 were significantly higher in the OPCABG group only at ICU admission (mean differences: 9.7 mm Hg, 95% confidence interval [CI] 3.1-16.2; and 27, 95% CI 6.1-47.7, respectively). The OPCABG group showed higher Paco2, overall ( P = .02) and at ICU admission (mean difference 1.8 mm Hg, 95% CI: 0.6-3), although mean values were always within normal range in both groups. No differences were seen in Sao2 values, time to extubation, rate of reintubation rate, and use of postoperative NIV. Extubation rate was higher in OPCABG only at postoperative hour 12 (92% vs ONCABG 82%, P = .02). Conclusion: The OPCABG showed only marginal improvements of unlikely clinical meaning in oxygenation as compared to ONCABG in elective low-risk patients.