Pulmonary perfusion reduces accumulation of neutrophils in the lung during cardiopulmonary bypass

Objectives

Exposure of blood to the foreign surface area of the bypass circuit is known to be associated with a complex 'whole body inflammatory reaction', which may contribute to the development of multiple organ dysfunction, including postoperative lung injury. Recently, we demonstrated lung ischemia during cardiopulmonary bypass (CPB). We therefore hypothesize that (1) lung ischemia induces an inflammatory reaction in the lung parenchyma and (2) that pulmonary perfusion during CPB reduces the inflammatory reaction of the lung.

Methods

Eighteen piglets (5.0 ± 0.5 kg) underwent 120 min of normothermic, total CPB without aortic cross-clamping, followed by 60 min of postbypass perfusion. Nine of them received continuous pulmonary perfusion with autologous, oxygenated blood during CPB while the pulmonary artery was clamped. Six additional piglets served as control and were ventilated after sternotomy for 180 min only.

Results

With the beginning of CPB, bronchial arterial blood flow decreased to 13% of the baseline value (42.1 ± 10.4 to 5.6 ± 1.0 ml/min), remained decreased until the end of CPB, and returned to starting levels 60 min after CPB. The decrease in bronchial blood flow was associated with a threefold increase in tissue lactate content. At the end of reperfusion there was a twofold increase in alveolar septal thickness and a significant accumulation of albumin, lactate dehydrogenase, neutrophils and elastase in the bronchioalveolar fluid as compared with control. Controlled pulmonary perfusion significantly ameliorated all of the observed changes.

Conclusions

(1) CPB causes a reduction in bronchial arterial blood flow, which is associated with injury to the lung. (2) Controlled pulmonary perfusion reduces injury to the lung during CPB. (3) The inflammatory response, as evidenced by the analysis of bronchoalveolar lavage fluid, may be caused by ischemia.