Causes of prolonged mechanical ventilation after coronary artery bypass surgery

Study objective: To evaluate causes of failure to be extubated (FTE) after coronary artery bypass graft (CABG) surgery. Design: Prospective observational study. Setting: Cardiovascular surgical ICU. Patients: Four hundred patients undergoing CABG surgery. Following surgery, patients were extubated by a standardized respiratory protocol and were assessed at 8, 24, and 48 h. Patients who could not be extubated at 8 h were designated as FTE, and at 24 and 48 h they were labeled as requiring prolonged mechanical ventilation (PMV) > 24 h and PMV > 48 h, respectively. Measurements and results: One hundred sixty-seven patients (41.75%), 27 patients (6.75%), and 21 (5.25%) patients, respectively, could not be extubated at 8, 24, and 48 h. Depressed level of consciousness was the most common reason for FTE in 58 of 167 patients (34.7%). The main cause of depressed level of consciousness was prolonged sedation due to anesthetic agents (51 patients; 30.5%). Hypoxemia was the most common cause for PMV for > 24 h (15 patients) and PMV > 48 h (13 patients). The causes of hypoxemia were cardiogenic and noncardiogenic pulmonary edema, pneumonia, and "hypoxemia of unknown etiology." Tachypnea due to acid-base disturbances was a reason for FTE and PMV for > 24 h in 27 and 3 patients, respectively. Cardiovascular instability was a rare reason for FTE. Postoperative bleeding was a cause for PMV in 18 patients. Four patients had more than a single reason for FTE at each assessment. Different causes have a variable effect on the duration of mechanical ventilation. Conclusion: The causes of PMV are heterogeneous, vary with time, and have a variable impact on the duration of mechanical ventilation required after the patient undergoes CABG surgery.