**4.5 Acute lung injury**

Impaired pulmonary function is a well-known complication of cardiac surgeries, however it has multiple factors to be related with such as anesthesia, temporary cardiac dysfunction, infused catecolamines, altered mechanics of thoracic cage, duration of mechanical ventilation, neurological, renal and infectious complications rather than a single factor; CPB being the mostly accused. Although it is not possible to perform all the cardiac procedures without CPB, avoiding bypass alone cannot prevent the lung injury completely (Apostolakis et al,2010).

Although there are limited, insufficient data supporting the broad clinical use heparincoated circuits and miniaturized circuits, minimizing the extracorporeal surface area and being biocompatible and free of any material that activates blood should lower the incidence of lung injury (de Vroege et al,2004). Leucocyte depletion may reduce the entrapment into lung capillaries, that in experimental studies it has been shown to reduce the heart and lung reperfusion injury (Apostolakis et al,2010,as cited in Bando et al,1990). Ultrafiltration and controlled hemodilution reduce interstitial lung edema, improving the lung functions after surgery (Apostolakis et al,2010). Using a controlled cardiac suction device, reducing the time between the contact of shed blood with pericardium and its re-transfusion, becoming activated only when the blood is accumulated in pericardium-minimizing air entrance may also improve lung functions. Furthermore, since the heparin level of pericardial blood is lower than systemic level, topical heparin administration may also diminish the inflammatory reactions contributing to lung injury (Tabuchi et al,1993).

Apnoea during CPB has been shown to be associated with increased incidence of pulmonary dysfunction. The results of clinical trials are conflicting, that some revealed improvement in lung functions by maintaining ventilation (with or without CPAP) together with pulmonary artery perfusion during CPB, whereas others revealed no difference (Stanley et al,1977;John et al,2008).

The rules of myocardial protection during ischemia and reperfusion, indirectly protect the lungs from several proinflammatory factors produced during the process (Apostolakis et al,2010).
