How long can donated blood be safely stored for transfusion?
In this month’s issue of Anesthesiology, Dr. Lorenzo Berra (Assistant Professor of Anesthesia, Department of Anesthesia, Critical Care and Pain Medicine, Harvard Medical School at Massachusetts General Hospital, Boston, Massachusetts) and coauthors examined whether donated blood stored for 40 days (40d blood) is as safe as donated blood stored for only 3 days (3d blood) and published their findings in the article “Transfusion of Stored Autologous Blood Does Not Alter Reactive Hyperemia Index in Healthy Volunteers.” Unfortunately, the study was not done merely as an academic exercise to improve our knowledge. As noted in the introduction of the article, there are retrospective studies showing that prolonged storage of donated blood may lead to worse clinical outcomes.
On the other hand, when I did a Google search of the phrase “blood bank shortage,” I received over 1 million hits. What is striking is that these reports are both national (Huffington Post) and local (Daily Iowan and Paragould Daily Press) from the past several weeks and have been reported consistently over a longer period of time with reports dating from 2011 and earlier.
With the current storage limit of 40 days, blood banks are able to store less common blood types as well as transfer the donated units needed between blood banks. If it turns out that blood banked more than 14 days is associated with worse outcome, then the existing shortage will become increasingly dire.
The challenge will be to weigh risk benefits of prolonged banked blood. If the choice is to have no banked blood available for a patient or to transfuse knowing that there may be adverse effects, physicians will find themselves in the proverbial Catch-22 and be forced to choose between the lesser of two evils.
This study tries to begin to help us answer these questions by controlling for all other variables and having the storage time as the only independent variable. The study population consisted of healthy, young adults (18-40 years…and which incidentally makes me no longer young!) who did not undergo surgery and who received either a 40d or 3d autologous blood transfusion. Each volunteer received both a 3d and 40d transfusion, and each transfusion was separated by a period of two weeks. The order of transfusion was randomized. In the study, the authors measured vital signs, blood levels of hemoglobin and other factors, and, indirectly, the nitric oxide levels. Fortunately they did not find a significant difference in vital signs or nitric oxide levels (via hyperemia index).
However, it is worth noting that these results were obtained from a population of healthy (and young) adults who were neither undergoing surgery nor were trauma patients, and they also did not receive massive transfusions. Hence, while we cannot forget about this issue, for now we ought to continue to be vigilant and weigh the risks vs. the benefits of transfusions.