Old blood may be bad blood, a study says today in the New England Journal of Medicine.
Researchers at the Cleveland Clinic found that heart surgery patients who got transfusions of blood that was more than two weeks old fared worse than those who received newer blood.
Researchers have long known that blood degrades over time, which is why the Food and Drug Administration does not allow it to be stored for more than 42 days -- although with constant blood shortages throughout the country, it often is used within several days of being donated.
But some have questioned whether 42 days is too long. As blood grows older, it loses power to bring oxygen to tissues.
"What we found was that patients who receive older blood don't do as well," study author Colleen Koch says.
In fact, the researchers write in the journal, "the relative risk of postoperative death is increased by 30 percent in patients given blood that has been stored for more than two weeks. These results may appear to suggest that blood should be classified as outdated earlier than current recommendations."
The report is one of the larger studies of old blood; records of 6,002 patients were examined. But some say it still does not definitively answer the question because it is what scientists call a "retrospective" study, meaning researchers studied records rather than designing a study from the beginning.
The study also applied to older patients (the median age was 70) having cardiac surgery, in which blood is put through the rigors of a cardiopulmonary-bypass pump.
"In this situation, old blood is not the best for these patients," says Celso Bianco, executive vice president of America's Blood Centers. But, he says, "I would encourage more studies in this area."
Richard Benjamin, chief medical officer of the American Red Cross, says that though the study is "provocative," it has weaknesses, and "it's not really appropriate to conclude that old blood is bad."
Koch says the Cleveland Clinic is designing a prospective, randomized, controlled trial to specifically address such questions.
Though transfusions often save lives in emergencies, it is not always clear that they're warranted, says Sunil Rao, assistant professor of medicine at Duke University. He did a study published in 2004 indicating that heart patients who received transfusions to treat blood loss or anemia actually fared worse than those who had received no transfusions at all.
"What if we subjected blood transfusion to the same type of testing we subject drugs to?" he asks. "Do you think it would get approved? I'm not so sure it would."
At the very least, patients and physicians should think seriously before giving any transfusion at all, both Rao and Koch say, let alone one with old blood.