To 1) determine risk factors for death when respiratory failure develops following cardiovascular surgery, 2) identify predictors of tracheostomy, and 3) define the utility of tracheostomy in this setting.
From 1998 to 2001, 846 of 12,928 patients (6.5%) who underwent cardiovascular surgery required postoperative ventilatory support ≥ 72 hours. Their preoperative, intraoperative, and intensive care unit (ICU) admission data were analyzed for factors associated with time-related competing risks of tracheostomy and death before tracheostomy. Risk-adjusted expected mortality was compared to observed mortality after tracheostomy.
At 7, 14, and 30 days, mortality was 11%, 15%, and 21%; tracheostomy frequency was 8%, 16%, and 21%. Risk factors for death without tracheostomy included long aortic clamp time (P=.001), acidosis (P<.0001), hypotension (P<.0001), lower cardiac index (P=.008), and need for vasopressin (P<.0001) at ICU admission. Predictors of tracheostomy were extremes of age (older, P<.0001; younger, P=.03), chronic obstructive pulmonary disease (P=.01), worse left ventricular function (P=.02), longer cardiopulmonary bypass time (P=.001), mitral valve replacement (P=.03), and aortic surgery (P=.03). Survival after tracheostomy (89%, 75%, and 32% at 14 and 30 days and 24 months) was worse than expected, based on status at ICU admission (91%, 85%, and 65% at these same intervals; figure).CONCLUSIONS: Respiratory failure following cardiovascular surgery portends an ominous outcome.
Worse-than-expected survival after tracheostomy suggests that it may not prevent mortality from respiratory failure, but rather identify a subset of patients less able to tolerate initial surgical stresses and the subsequent postoperative course.
S.C. Murthy, None.