Despite these data, the continuum between pulmonary dysfunction and overt complications has been poorly characterized. Because such complications considerably jeopardize outcomes and imply increased health-care costs and resource utilization, their prevention, early identification, and effective treatment is highly advisable. Preventive measures have been authoritatively described elsewhere [4, 5]. Refinements of operative techniques and cardiopulmonary bypass and mechanical ventilation strategies, meticulous application of “ventilator care bundles,” rational and early use of antibiotics, early extubation, and judicious blood management have all been advocated for a thorough preventive management algorithm. Acute respiratory distress syndrome, transfusion-related lung injury, and ventilation associated pneumonia, though infrequent, are the most dreaded of these complications because of inherent dismal outcomes.

Weaning from mechanical ventilation is essential to the success of the cardiac surgical procedure and a key step toward recovery and rehabilitation. The combination of several respiratory and cardiovascular parameters is known to improve the accuracy of prediction of successful weaning from ventilator support. Nevertheless, the same parameters perform poorly in the prediction of late extubation failure. Today, pulmonary complications account for 54.9 % of intensive care unit (ICU) recidivism and reintubation is needed in at least 6.6 % of the patients [6]. Causes of post-extubation failure include both airway (such as upper-airway obstruction, aspirations, and excess pulmonary secretions) and non-airway-related factors (including cardiogenic dysfunction). Pathophysiology of post-extubation failure usually includes two distinct pathways: (1) alveolar hypoventilation and ventilation-perfusion mismatch, due to increased respiratory rate and decreased tidal volume, and (2) a failure to increase cardiac output, which leads to an enhanced tissue oxygen extraction with critically low mixed venous oxygen saturation [7]. Reintubation prolongs the duration of invasive mechanical ventilation and increases the need for tracheostomy. Loss of airway-protecting mechanisms, airway trauma, intense sedation, and the potential for aspiration are some of the drawbacks of invasive ventilation that predispose to the development of ventilator-associated pneumonia and extend the length of the ICU and hospital stay, implying higher morbidity and mortality. A pivotal study by Hein and coworkers [8] on a contemporary series of cardiac surgery patients disclosed that hospital mortality in the event of respiratory failure is as high as 38 % and the chance of 3-year survival is lower than 45 %.

These findings emphasize the importance of both determining perioperative predictors of extubation failure and implementing new preventive and curative modalities that avoid the constraints of conventional invasive ventilation. Studies on predictors of reintubation and mechanical ventilation after prior successful weaning from ventilator support and extubation in the cardiac surgery setting are few. Back in 1999, a study conducted at the Mayo Clinic elegantly disclosed that preoperative predictors commonly occur either as single or multiple features in this patient subset, however, the author demonstrated that it is the combination of adverse intraoperative events with baseline disease process and laboratory and hemodynamic perturbations that compounds the risk of extubation failure in the individual patient. Indeed, difficult surgery (redo procedures, procedures involving the thoracic aorta or the placement of ventricular assist devices, those implying lengthy cardiopulmonary bypass time or massive transfusions of blood products) usually impact on the individual patient frailty as portrayed by surrogate markers of inadequate baseline cardiorespiratory reserve (chronic obstructive pulmonary disease, pulmonary hypertension, low left ventricular ejection fraction) and preoperative hematological and biochemical abnormalities (anemia, hypoalbuminemia, increased blood urea nitrogen and/or creatinine) [9]. Studies that are more recent substantially added to this knowledge and further stressed the role of prolonged primary intubation, because the longer the initial ventilator support, the higher the chance of extubation failure [2–5]. The clinical bottom line is that identification of patients at risk may, and, actually, should take place as early as ICU admission and should prompt alternate management algorithms.