Effects of pulmonary artery perfusion on gas exchange and alveolar matrix metalloproteinases after cardiopulmonary bypass in a swine model

Background: The lung is the least protected organ during cardiopulmonary bypass (CPB). The present pilot-study was designed to determine the effects of the infusion of cooled, oxygenated blood into the pulmonary artery as hypothermic lung perfusion (HLP) on gas exchange and inflammation after CPB in an animal model. Methods: Pigs were randomly assigned to a control group (n=6) undergoing CPB with moderate hypothermia and 60 minutes of cardioplegic cardiac arrest or an intervention group being additionally treated with 45 minutes of HLP during aortic crossclamping. The alveolo-arterial O2-gradient (AaDO₂), the concentrations of the metalloproteinases (MMP) 2 and 9 in bronchoalveolar lavage (BAL), and the relative count of nucleophils (RCN) were determined. Results: AaDO₂ increased in both groups but was lower after CPB in the HLP in comparison with the control group (384 ± 146 vs 542 ± 75 after 120 minutes; 377 ± 172 vs 541 ± 73 after 180 minutes; p<0.05). The RCN decreased in the HLP group compared to control immediately after CPB (p<0.05) while the MMPs 2 and 9 increased in both groups without any difference after 180 minutes. Conclusions: This suggests that HLP may improve pulmonary gas exchange and that this may - at least in part - be related to a decrease in post-CPB pulmonary inflammation.