Outcomes for difficult-to-wean subjects after cardiac surgery

The need for prolonged mechanical ventilation (PMV) after cardiac surgery is still a common problem. We hypothesized that subjects who required PMV after a single surgery (either coronary artery bypass grafting or valve surgery) would have better outcomes than those who had experienced both revascularization and valve surgery.

We retrospectively analyzed the characteristics and outcomes for patients consecutively admitted to our weaning unit (WU) after cardiac surgery between December 2007 and August 2012. Subjects' data were analyzed according to the number of procedures. Group 1 included subjects who had undergone a single surgery (valvular replacement or myocardial revascularization). Group 2 included subjects who had undergone combined surgery (valvular replacement and myocardial revascularization). Data for PMV subjects who were transferred to the WU for reasons other than cardiac surgery in the same period are also reported.

Of 584 PMV subjects admitted, 35 (5.9%, 19 in group 1 and 16 in group 2) were referred after cardiac surgery. At WU admission, group 2 showed significantly more comorbidities and a greater clinical severity than group 1. Compared with group 1, group 2 showed a significantly lower weaning rate (43.7% vs 78.9%, P = .003) and a higher in-hospital mortality (31.3% vs 5.3%, P = .04). The overall 6-month survival for subjects of group 1 was 73.7% compared with 37.5% for subjects in group 2 (P = .02). Adjusting for comorbidities and clinical severity, the difference between the 2 groups did not reach statistical significance for either the weaning rate or the overall 6-month survival. At discharge, health status, as assessed by means of functional independence measure, was significantly better in group 1 than in group 2 (P = .035).

These results suggest that patients needing PMV after combined cardiac surgery may suffer worse outcomes than those needing PMV after simple cardiac surgery.