There was a time when I, in a previous incarnation as a blood banker, spent a lot of time thinking about the shelf life of blood and how to increase the utilization of blood in blood bank inventory. Hence, a recent article about this topic caught my eye, partly out of a sense of nostalgia (see: The Shelf Life of Donor Blood). Here is an excerpt from it:
For decades, the Food and Drug Administration has limited storage of refrigerated red blood cells to 42 days. But it has been clear for some time that stored blood degrades in various ways long before that six-week limit, and some research suggests that the changes may be harmful to patients who receive older blood. Now a study published in the journal Anesthesia & Analgesia has found that after even 21 days, the membranes of stored blood cells have stiffened, apparently the result of damage over time. That’s a problem because red blood cells are about the same diameter as small capillaries, and they have to change shape to get through.....“What we showed is that the cell membranes lose their flexibility,” said the lead author, Dr. Steven M. Frank....“That makes it more difficult for them to travel through.” The study also found that the older blood cells did not recover their flexibility after being transfused into patients, unlike certain other kinds of changes that blood cells undergo during storage. For example, nitric oxide, essential to keep blood vessels open, is depleted from cells after a few hours of storage, but is restored rapidly after transfusion. Still, researchers do not fully understand the importance of such findings to clinical practice. Even permanent changes in cell structure may not matter, according to [another expert]. “You constantly have blood cells that are getting old in your body, and they’re filtered out,” he said. “It may be that that same system harmlessly filters out these structurally abnormal blood cells.” Two large randomized clinical trials have been undertaken to clear up some of the uncertainties about stored red blood cells.....Dr. Richard J. Benjamin, chief medical officer at the Red Cross, said the two trials would provide important information. If older blood turns out to be less effective, he said, “there are a couple of ways we can respond.” “There are already better storage solutions in development that show drastically improved biochemistry parameters,” he said. “Is the next step to restrict the age of blood for vulnerable populations? ....” As the system works now, the newest blood goes to hospitals that do transfusions infrequently. This gives them time to store the blood safely until it is needed. But it leaves hospitals that use the most blood — trauma hospitals and academic medical centers — with the older blood.
Some highly esteemed hospitals now hold the view that most blood transfusions should be avoided. In short, they view blood transfusion with a jaundiced eye (see: Avoiding Blood Transfusion as a Hospital Quality and Cost-Savings Measure; The Value of a Restrictive Blood Transfusion Strategy for Hospitalized Patients). These hospitals are establishing policies to discourage transfusions on the basis of both cost and quality concerns. Such policies extend beyond the risk of transmitting infectious disease with the blood. I personally don't think that there will be a rapid drop in demand for blood regardless of the results of the two randomized clinical trials referred to in the excerpt above. It's often hard to get older physicians to accept new policies. Rather, I suspect that demand for blood may gradually level off and perhaps even go down slightly in the near future as these anti-transfusion policies extend beyond the few places where they have been already implemented.