Factors associated with prolonged mechanical ventilation following coronary artery bypass surgery

Study objectives: To identify the typical duration of postoperative mechanical ventilation following coronary artery bypass graft surgery (CABG), and to identify risk factors for prolonged postoperative ventilation. Design: Retrospective study of 4,863 consecutive patients using univariate and multivariate survival analysis to identify independent risk factors. Setting: Saint Thomas Hospital, Nashville, TN, a 575-bed, academically affiliated, regional referral hospital specializing in cardiovascular diseases. Patients: All patients undergoing CABG in our hospital from January 1, 1996, to December 31, 1997. Interventions: None. Measurements and results: Duration of mechanical ventilation and mortality were measured. More than 94% of the patients were extubated in the first 3 days following surgery, 4% more were extubated from postoperative days 4 to 14, and almost 2% were receiving ventilation for > 14 days. Those risk factors that reflect preoperative medical instability, especially cardiac or respiratory insufficiency, were associated with the highest incidence of prolonged postoperative mechanical ventilation and for operative mortality. The Society of Thoracic Surgeons-predicted mortality estimate was the best single independent predictor for prolonged postoperative ventilation. Conclusions: Typically, patients can be expected to be extubated within 3 days after CABG. Certain preoperative comorbidities, especially preoperative cardiac or respiratory instability, are predictive of prolonged postoperative mechanical ventilation.