Risk of Transfusion in Isolated Coronary Artery Bypass Graft: Models developed from the STS Database

BACKGROUND Perioperative blood transfusion is associated with adverse outcomes and higher costs following coronary artery bypass graft surgery (CABG). We developed risk assessments for patients’ probability of perioperative transfusion and the expected transfusion volume, to improve clinical management and resource use. METHODS Among 1,266,545 consecutive (2008-2016) isolated-CABG operations in STS’s Adult Cardiac Surgery Database, 657,821 (51.9%) received perioperative blood transfusions (red blood cell [RBC], fresh frozen plasma [FFP], cryoprecipitate, and/or platelets). We developed “full” models to predict perioperative transfusion of any blood product, and of RBC, FFP, or platelets. Using least absolute shrinkage and selection operator model selection, we built a rapid risk score based on 5 variables (age, body surface area, sex, preoperative hematocrit and use of intra-aortic balloon pump). RESULTS Full model C-statistics were 0.785, 0.815, 0.707, and 0.699 for any blood product, RBC, FFP, and platelets. Rapid risk assessments’ C-statistics were 0.752, 0.785, 0.670, and 0.661 for any blood product, RBC, FFP, and platelets. The observed versus expected risk plots showed strong calibration for full models and risk assessment tools; absolute differences between observed and expected risks of transfusion were <10.8% in each percentile of expected risk. Risk-assessments’ predicted probabilities of transfusion were strongly and non-linearly associated (p<.0001) with total units transfused. CONCLUSIONS These robust and well-calibrated risk assessment tools for perioperative transfusion in CABG can inform surgeons regarding patients’ risks and number of RBC, FFP, and platelets units they can expect to need. This can aid in optimizing outcomes and increasing efficient use of blood products.