Anemia and blood transfusion and outcome on the intensive care unit

The observation of Sakr and colleagues that transfusion may be beneficial in certain subgroups of intensive care unit (ICU) patients [1] is interesting, since large observational studies demonstrate that transfusion is independently associated with an increased risk of death [2]. Also, a systematic review showed that the benefits of transfusion in the ICU do not outweigh the risks [3]. Sakr and colleagues ascribe their discrepant results to the fact that transfused blood was leukoreduced. Of the 17 randomized controlled trials on the association of nonleukoreduced blood with mortality, however, a benefit of leukoreduction was found only in cardiac surgery patients [4]. A meta-analysis confirmed that available evidence does not justify universal leukoreduction [5]. Given the increased risk of nosocomial infection, multiple organ failure and acute respiratory distress syndrome, an explanation of a beneficial effect from transfusion in anemic critically ill patients is tempting. We propose that the results of this study may be related to the indication of transfusion, this being active bleeding and not correction of anemia associated with critical illness. Hereby, transfusion may have prevented adverse events due to postoperative bleeding, explaining the survival benefit. The fact that 76% of patients were referred from the operating/recovery room and that the median length of ICU stay was only 1 day may support this hypothesis. Based on numerous reports on the association of transfusion with adverse outcome, a liberal transfusion strategy in critically ill anemic patients in the absence of acute bleeding should not be advocated.