Mechanical Ventilation During Cardiopulmonary Bypass.

Abstract

DESPITE PROGRESS IN perioperative management, postoperative pulmonary complications (PPCs) still are a leading cause of morbidity and mortality in cardiac surgery. About 25% of patients with no severe cardiac dysfunction who undergo cardiac surgery experience significant respiratory impairment for at least 1 week after the intervention. Post-cardiac surgery PPCs clinically range from fever with productive cough to acute respiratory distress syndrome (ARDS), requiring prolonged mechanical ventilation (MV) and showing reduced survival. Cardiopulmonary bypass (CPB) is necessary for the majority of procedures in cardiac surgery, making CPB-related lung damage inevitable. Inflammatory response after CPB, exclusion of lung tissue from perfusion and ventilation, and atelectasis due to airway collapse are the most important factors implicated in CPB-related lung injury. Cardiac anesthesiologists commonly need to address post-cardiac surgery respiratory failure and PPCs, such as pneumonia, atelectasis, pleural effusion, diaphragm dysfunction, and ventilation-associated pneumonia, which carry a high burden of morbidity and mortality. Regardless of any specific complication, impairment of gas exchange, reflected by a reduction in the PaO2/FIO2 ratio (the ratio between arterial blood oxygen partial pressure and inspired air oxygen fraction), frequently occurs after cardiac surgery and has been associated with poor hospital outcome, although accurate validation of this parameter in this setting is lacking. A PaO2/FIO2 value of 300 or less indicates reduced efficiency in alveolar-capillary membrane performance. A detailed definition of PPCs can be found in Table 1. The aim of this review was to summarize the evidence in the literature concerning CPB-related lung dysfunction and to show how MV strategies might prevent respiratory insufficiency after cardiac surgery.