In this article, Ferraris and coworkers attempt to identify patient characteristics that can differentiate patients who will benefit from allogeneic blood transfusion from patients who may be harmed by transfusion. Statistical analyses were performed on surgical patients entered between 2010 and 2012 into the database of the American College of Surgeons National Surgical Quality Improvement Project. This database includes more than 50 demographic and preoperative clinical risk variables as well as 30-day morbidity and mortality related to operative procedures submitted by more than 300 acute care hospitals throughout the United States. Excluded were trauma and pediatric surgery as well as operations on cardiopulmonary bypass. In order to explore the relationship between allogeneic transfusion and operative mortality, 10 patient groups were created from the database with increasing predictive risk of mortality and with equal numbers of deaths in each decile group.

Of 470,407 patients entered into the database, 32,953 (7%) received at least one single blood transfusion within 72 hours of the surgical procedure. The proportion of transfused patients who died or developed serious morbidity was 11.3% and 55.4%, respectively, compared with 1.3% and 6.1% in non-transfused patients (P < 0.001). The adverse effects of transfusion were dose-dependent. Preoperative risk variables had excellent predictive accuracy for the probability of operative mortality. Overall, sicker patients were more likely to receive transfusions. Operative high-risk patients (ASA class IV, preoperative cancer, preoperative sepsis, liver failure with ascites, emergency operations, dialysis dependency, congestive heart failure, chronic obstructive pulmonary disease and others) had a minimal risk associated with allogeneic transfusion and benefited the most from transfusion, whereas the patients at lesser perioperative risk had an 8- to 12-fold increase in the odds of developing serious morbidity or mortality associated with allogeneic transfusion. Interestingly, only 6% of patients presented preoperative anaemia and only one third of these patients were finally transfused. However, the situation with the greatest risk for adverse surgical outcomes was the combination of preoperative anaemia and allogeneic transfusion. These observations are limited by the difficulty to statistically identify allogeneic transfusion as an independent risk factor in the presence of a variety of other major risk factors. – Oliver Habler

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