Facing surgery? You could receive blood that has been stored for a week, three weeks or nearly six — and there's growing concern that people who get the older blood might not fare as well.
It's a question with big implications for the nation's already tight blood supply.
Blood is rotated almost like milk in a store: The Food and Drug Administration allows red blood cells to be stored for 42 days, and hospitals almost always use the oldest in their refrigerators first to ensure none expires. How old the blood you receive is depends on how much the hospital has of your type that day. The average age of transfused blood is just over 16 days.
This summer, hospitals across the country are launching major new research to try to settle if fresher blood really is better for at least some patients. And if so, they're hunting ways to turn back the clock for older blood and offset any deterioration.
Donated blood "saves lives every day. We certainly do not want to run out of it," says Dr. Simone Glynn of the National Institutes of Health, which is spearheading the multimillion-dollar studies.
But if shelf life is proven to make a difference, then "how can we have the safest product possible?" asks Glynn, transfusion medicine chief at NIH's National Heart, Lung and Blood Institute.
Those attempts range from trying to improve the oxygen-carrying capacity of stored blood to ridding it of so-called microparticles, cell fragments that gradually build up in storage.
Scientists have long known that blood breaks down the longer it's stored, but not whether those changes were enough to trigger side effects.
Several years ago, a number of small studies began suggesting that blood well under the FDA's 42-day storage limit may increase the risk of complications.
Enter the more stringent research to find out:
• In the largest NIH-backed study, 15 hospitals will recruit 1,800 patients about to have heart surgery who agree to be randomly assigned to get blood more than 20 days old or less than 11 days old, and then track how they fare. (Patients who don't participate would get older blood anyway, per standard hospital policy.)
• In Canada, researchers are enrolling 2,500 patients in critical-care units into a similar study that defines "fresh" as no older than a week. Separately, they're also studying the question in several hundred premature infants who need blood.
• The Cleveland Clinic has enrolled about 1,000 heart-surgery patients and counting into another comparison, this one defining fresh as no older than two weeks.
At the same time, the NIH is funding eight additional projects to explore what happens to stored blood that might trigger side effects.