Risk analysis for readmission after coronary artery bypass surgery: developing a strategy to reduce readmissions

Background: Readmission within 30 days of adult cardiac surgery procedures is a frequent contributor to the costs of cardiac surgery hospitalizations, but current data regarding risk factors for readmission are limited. We therefore sought to analyze quality improvement risk factors for readmissions after coronary bypass surgery (CABG).

Study design: The records of patients undergoing CABG at our institution from July 2006 to June 2011 were evaluated for variables with potential literature-based associations with readmission, including New York Cardiac Surgery Reporting System (CSRS) risk factors, discharge medications, and laboratory values.

Results: The readmission rate was 13% (n = 158 of 1,205); the CSRS predicted rate was 8.7% (observed/expected ratio = 1.5). Median time from CABG discharge to readmission was 6 days (interquartile range [IQ] 3 to 13 days). Median readmission length of stay was 4 days (IQ 2 to 7 days). The most frequent reasons for readmission were cardiac (n = 40 [25% of readmissions]) and pulmonary complications, including pleural effusions (n = 36 [23%]). Beyond CSRS risk factors, only abnormal discharge serum creatinine was associated with increased readmission (p = 0.05). Combining CSRS risk variables for government insurance and unplanned reoperation led to the highest readmission risk (odds ratio [OR] 5.7, 95% CI 1.7 to 18.7).

Conclusions: Coronary bypass surgery readmissions remain a persistent clinical challenge. Given that readmissions often occur within the first week postdischarge and are typically of short duration, post-CABG readmissions may be reduced through careful postoperative surveillance for readmission risk factors (eg, abnormal serum creatinine or unplanned reoperations) and/or for frequent causes of readmission (eg, pleural effusions).