More than a decade has passed since the publication of the results of the Transfusion Requirements in Critical Care (TRICC) trial, supporting the restriction of red blood cell (RBC) transfusions in the gravest patients1. Since then, some reports are indicative of improvements in transfusion practices (mostly as regards reduced haemoglobin [Hb] thresholds at which patients are transfused2–4). Nonetheless, the overall use of allogeneic RBC transfusions in clinical practice remains relatively high and still varies widely among many centres and practitioners5–7. The latest data from the U.S. Department of Health and Human Services indicate that over 14.6 million units of RBC or whole blood were transfused in the USA in 2006, which is a 3.3% increase from the previous report8. Similarly, the Agency for Healthcare Research and Quality (AHRQ) reported that in 2007, blood transfusions were given in one in every ten hospital admissions in which a procedure was performed; this is a 140% increase from 1997, making transfusion the fastest growing common procedure in hospitals in the USA9.
Allogeneic blood transfusions have historically been linked with a myriad of risks and complications. Some risks (e.g. transfusion reactions and transmission of pathogens) have been largely mitigated through advancements in blood banking (e.g. screening for antibodies and markers of infective agents), although these risks are not likely to ever be completely eliminated10,11. Some other risks and complications (e.g. immunomodulation and transfusion-related acute lung injury [TRALI]) appear to have more subtle and elusive aetiologies and are more difficult to tackle11. The presence of leukocytes, residual plasma, and the effects of blood storage have been investigated as possible causes of harmful consequences of banked allogeneic blood12–15. Notably, a number of clinical trials on the effects of storage age of blood on patients’ outcomes are underway: the results of these trials could substantially change the transfusion practice landscape, if they demonstrate that the currently accepted shelf-life of banked blood is too long and should be revised16–19. The other potential threat to safe, readily available transfusions is the aging population which could result in more recipients and fewer donors, putting more pressure on the less than 10% margin that currently exists between the number of collected and transfused blood units8. Finally, direct and indirect costs associated with transfusion have been rising steadily20, providing another motivation for improving transfusion practices.