Comparative Study of Postoperative Pulmonary Gas Exchange Between On-pump or Off-pump Coronary Artery Bypass Operations

Abstract

Objective: Pulmonary dysfunction is one of the postoperative morbidities that my links to use of cardiopulmonary bypass (CPB).The beating heart (off-pump) technique for coronary artery bypass grafting (CABG) aims to avoiding some complications related to using cardiopulmonary bypass (CPB). In this study, we compared postoperative pulmonary gas exchange between on-pump and off-pump coronary artery bypass operations. 

Methods: Fifty patients (mean age 60.4±8.4 years) with no preexisting lung disease and good left ventricular function undergoing primary CABG were randomized to undergo surgery with or without CPB assistance. Alveolar/arterial oxygen pressure gradients [P(A-a)O₂] were estimated preoperatively with patients breathing air, then 2-4 hours postoperatively during mechanical ventilation with three different oxygen concentrations (30%, 40%, and 60%), and again 1 hour after extubation while breathing the same three oxygen concentrations. 

Results: Preoperative P(A-a)O₂ gradients on air were equal in the two groups. Postoperatively and during mechanical ventilation, gradients increased with the increase in inspired oxygen fraction concentrations, but there were no significant differences in P(A-a)O₂ gradient between the two groups, either during ventilation or after extubation. 

Conclusions: The study points that off-pump surgery is not associated with superior pulmonary gas exchange in the first hours after routine CABG in patients with uncompromised pulmonary and left ventricular functions