Predicting blood usage in cardiac surgery--the transfusion predictor product.

Blood cross-matched for patients undergoing cardiac surgery is used infrequently and represents a significant cost. We investigated the ability to predict the need for intraoperative transfusion. We hypothesized that red blood cell volume is a predictor because dilution is the primary cause for transfusion requirement intraoperatively. A total of 401 consecutive patients having cardiothoracic surgery requiring the use of cardiopulmonary bypass were retrospectively analyzed by revision of their perfusion record. This sample included 82% elective, 17% urgent, and 1% emergency procedures. The product of body surface area and preoperative hemoglobin gave us gHb/l/m2, which are the units of the Transfusion Predictor Product (TPPU). Mean patient age was 66.9 +/- 10.7 years, and 112 (28%) were women. Mean TPP was 257.2 +/- 45.5u. 52 patients (13%) received red blood cells intraoperatively. At less than TPP 211.7u, one standard deviation below the mean value, 32 patients of 69 (46%) received blood transfusion intraoperatively (p < 0.001). At a TPP greater than 211.7u, 20 patients of 322 (6%) had blood transfusion intraoperatively. Patients with a TPP > 211.7u do not require routine cross-matching of blood. Cross-matching for these patients should be individualized on the basis of predicted duration of CPB and/or other types of patient comorbidity.