Mechanical ventilation during cardiopulmonary bypass improves outcomes mostly upon pleurotomy

We read with great interest a recently published article in the journal by Rodríguez-Lima et al. [1]. They revealed that among neonates undergoing cardiac surgeries for the correction of either transposition of the great arteries with or without ventricular septal defect or aortic arch hypoplasia with or without ventricular septal defect, the implementation of mechanical ventilation during cardiopulmonary bypass (CPB) attenuated postoperative serum concentrations of C-reactive protein, mechanical ventilation time and vasoactive-inotropic score. In addition, there was a trend towards decreasing intensive care unit length of stay. Given their valuable and practical findings and appearing in the studies, we believe that some notions need to be taken into considerations in the future.

The reasons that cardiac surgeons do not like to continue ventilation during CPB are the idea of ventilation–perfusion mismatch and the lack of consensus or adequate data on its positive effect. But more importantly, the movement of the cardiac surgery field with ventilation disturbs meticulous surgical procedure. Most investigations on this subject have shown that CPB without mechanical ventilation is associated with a decrease in Pao₂/Fio₂ ratio, arterial pH and a reduction in the respiratory system’s static compliance as well as increases in PaCo₂, pulmonary shunt and the alveolar-arterial oxygen gradient. On the other hand, ventilation throughout CPB caused decreased interstitial oedema and polymorphonuclear infiltration in the lung parenchyma [2]. According to our prior investigations, a considerable increase in the incidence of pulmonary complications is due to pleurotomy and the subsequent atelectasis during cardiac surgery with off-ventilation [3, 4], the same finding that other study reached [5]. An experimental study by da Costa Freitas et al. [2] revealed that pigs receiving lung ventilation and perfusion during CPB with opening pericardium and both pleura had histologic findings suggestive of attenuated pulmonary inflammation and injury. For patients undergoing thoracic surgeries, continuous ventilation has been advised for decreasing iatrogenic atelectasis caused by the opening of pleural space [6].

So the neglected points in the studies like the study of Rodríguez-Lima et al. that compared on- and off-ventilation during CPB are opening of the pleura and subsequent atelectasis that surely affect postoperative pulmonary function.

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