The influence of selective pulmonary perfusion on the inflammatory response and clinical outcome of patients with chronic obstructive pulmonary disease undergoing cardiopulmonary bypass

Abstract

Patients undergoing cardiac surgery presenting with chronic obstructive pulmonary disease (COPD) have a higher 30-day mortality risk. In these patients, pulmonary dysfunction linked to an inflammatory response is frequent after cardiac operations using cardiopulmonary bypass (CPB), which causes pulmonary hypoperfusion. We hypothesize that selective pulmonary perfusion (sPP) of the lungs leads to a reduction of pulmonary inflammation and a better clinical outcome. Fifty-nine COPD patients (forced expiratory volume in 1 s/vital capacity <70%) undergoing cardiac surgery procedures (coronary artery bypass grafting 64%, valve 14%) were block-randomized to sPP (venous blood, temperature 2°C, 4 l) or standard CPB (28/28). The primary end-point of the study was to evaluate the effect of pulmonary perfusion on gas exchange by measuring alveolar-arterial oxygen gradient. The surrogate end-points were inflammatory response, intensive care unit (ICU) stay, time on respirator (TOR) and major adverse cardiac and cerebrovascular events. A cytokine assay for interleukin-1β, IL-6, IL-10, tumour necrosis factor-α (TNF-α) and polymorphonuclear elastase was performed with peripheral blood at different time-points [(t1) pre-CPB, (t2) end of CPB, (t3) 3 h, (t4) 24 h, (t5) 48 h postoperatively]. Repeated-measure analysis of variance and non-parametric statistics were used to assess the between-group and during time differences. The two groups proved comparable for perioperative variables. Serum cytokines were not different in the two groups throughout the study (P > 0.05 at single time-points), but as a function of time, the markers of the inflammatory response increased after CBP (P < 0.05 pre-CPB to 24 h). Clinical end-points were statistically comparable in both groups, but with a trend towards a shorter TOR (72 ± 159 h/106 ± 193 h) and ICU stay (3.9 ± 7.2 days/5.5 ± 9.2 days) in the sPP group despite a slightly longer time on extracorporeal circulation (120 vs 158 min). These results indicate a non-significant trend that repeated hypothermic lung perfusion with venous blood during CPB may have a protective effect on the lungs. A multicentre study design and larger cohort seem necessary to demonstrate the benefits of sPP more clearly.