A novel score to estimate the risk of pneumonia after cardiac surgery

Objective The purpose of this study was to derive and validate a risk score for pneumonia (PNA) after cardiac surgery. Methods Adults undergoing cardiac surgery between 2005 and 2012 were identified in a single-institution database. The primary outcome was postoperative PNA. Patients were randomly assigned to training and validation sets in a 3:1 ratio. A multivariable model was constructed incorporating univariate pre- and intraoperative predictors of PNA in the training set. Points were assigned to significant risk factors in the multivariable model based on their associated regression coefficients. Results A total of 6222 patients were included. The overall rate of postoperative PNA was 4.5% (n = 282). A 33-point score incorporating 6 risk factors (age, chronic lung disease, peripheral vascular disease, cardiopulmonary bypass time, intraoperative red blood cell transfusion, and pre- or intraoperative intra-aortic balloon pump) was generated. The model used to generate the score in the training set was robust in predicting PNA (c = 0.72, P <.001). Predicted rates of PNA increased exponentially with increasing risk score, ranging from 1.2% (score = 0) to 59% (score = 33). There was significant correlation between predicted rates of PNA based on the training cohort and actual rates of pneumonia in the validation cohort in weighted regression analysis (r = 0.74, P <.001). The composite score outperformed the STS prolonged ventilation model in predicting PNA in the validation cohort (c-index 0.76 vs 0.71, respectively). Conclusions This 33-point risk score is strongly predictive of postoperative PNA after cardiac surgery. The composite score has utility in tailoring perioperative management and in targeting diagnostic and preventative interventions.