Pulmonary collapse alone provides effective de-airing in cardiac surgery: a prospective randomized study

Objectives: We previously described and showed that the method for cardiac de-airing involving: (1) bilateral, induced pulmonary collapse by opening both pleurae and disconnecting the ventilator before cardioplegic arrest and (2) gradual pulmonary perfusion and ventilation after cardioplegic arrest is superior to conventional de-airing methods, including carbon dioxide insufflation of the open mediastinum. This study investigated whether one or both components of this method are responsible for the effective de-airing of the heart. Methods: Twenty patients scheduled for open, left heart surgery were randomized to two de-airing techniques: (1) open pleurae, collapsed lungs and conventional pulmonary perfusion and ventilation; and (2) intact pleurae, expanded lungs and gradual pulmonary perfusion and ventilation. Results: The number of cerebral microemboli measured by transcranial Doppler sonography was lower in patients with open pleurae 9 (6-36) vs 65 (36-210), p=0.004. Residual intra-cardiac air grade I or higher as monitored by transesophageal echocardiography 4-6 minutes after weaning from cardiopulmonary bypass was seen in few patients with open pleurae 0 (0%) vs 7 (70%), p=0.002. Conclusions: Bilateral, induced pulmonary collapse alone is the key factor for quick and effective de-airing of the heart. Gradual pulmonary perfusion and ventilation, on the other hand, appears to be less important.