Hospital variability in length of stay after coronary artery bypass surgery: results from the Society of Thoracic Surgeon’s National Cardiac Database

Background. There is growing interest in comparing resource, as well as patient outcome metrics among coronary artery bypass graft surgery (CABG) providers, yet few tools exist for adjusting these provider comparisons for patient case-mix. In this study, we aimed to define the magnitude of hospital variability in postoperative length of stay (PLOS) in contemporary practice and to determine the degree to which this variability was accounted for by differences in patient case-mix. We also sought to determine the relationship between hospitals’ risk-adjusted PLOS and mortality outcomes. Methods. We analyzed 496,797 isolated CABG procedures performed between January 1997 to January 2001 at 587 US hospitals participating in the Society of Thoracic Surgeon’s National Cardiac Database. Logistic and linear regression were used to identify independent preoperative factors affecting a patient’s likelihood for early discharge (PLOS ≤5 day), prolonged stay (>14 days), and overall PLOS. Hierarchical models were used to determine the degree to which hospital factors influenced PLOS beyond patient factors. Results. Overall, 53% of CABG patients were discharged within 5 days of CABG, whereas 5% required prolonged (>14 days) stays. More than 25 preoperative patient factors were independently associated with a patients’ likelihood for early discharge and prolonged stay (model C index 0.70 and 0.75, respectively). After adjusting for patient factors, however, there remained wide unexplained variability among hospitals in PLOS and limited correlation between these PLOS metrics and hospitals’ risk-adjusted mortality results (Spearman correlation coefficient −0.15 and 0.35). Conclusions. Our study provides a method for institutions to receive meaningful risk-adjusted bypass PLOS information. Given the marked variability among hospitals in CABG PLOS, institutions should consider benchmarking metrics of efficiency, as well as patient outcomes.