Older donated blood tied to heart surgery risk
Study backs fresher transfusions
By Stephen Smith, Globe Staff | March 20, 2008
Patients undergoing heart surgery routinely receive blood that has sat on a refrigerator shelf for two weeks or longer, a practice that appears to heighten their risk of infection, kidney failure, and even death, according to a major new study.
The sweeping report in today's New England Journal of Medicine found that the age of donated blood may prove more critical than previously recognized. Scientists from the Cleveland Clinic discovered that cardiac surgery patients who received blood that was more than two weeks old were 30 percent less likely to be alive a year later than those transfused with fresher blood.
"It's like produce or meat - it has a limited shelf life," said Dr. Colleen Gorman Koch, who directed the research.
Specialists said the findings underscore the need to minimize transfusions, boost the stockpile of donated blood, and consider making sure the freshest blood gets to patients who need it the most. Chronically in short supply, blood can be stored for up to six weeks before federal rules dictate that it must be discarded.
"Increasingly, there's awareness that blood transfusion is not a free lunch, that there are quite significant hazards associated with its use," said Dr. James Rawn, director of the cardiac surgery intensive care unit at Brigham and Women's Hospital. "The importance of this study for me as a practitioner is to more strongly confirm that, ideally, we'd like to do heart surgery without giving any blood products."
The study, which tracked 6,002 patients who underwent bypass or valve replacement surgery, is believed to be the largest attempt ever to measure whether the age of donated blood affects the well-being of recipients.
Like sutures and scalpels, sacks of blood are a prominent feature in hospital operating rooms, with nearly half of all heart patients getting at least one pint. Surgeons have historically not known the age of the blood they are giving, and it's generally impossible for patients to have any control over the blood they receive.
Scientists have known for a while that the longer blood sits unused, the more it degrades. Doughnut-shaped red blood cells inexorably lose flexibility, until they become more like stale doughnuts, incapable of traveling efficiently through narrow blood vessels. They also forfeit their ability to efficiently deliver oxygen to tissue, depriving organs of the fuel they need and putting them at risk of failure.
When blood is fresher, "it's as if you rent a truck and you have something which has a ramp, as opposed to having to lift it up and lug" in oxygen, which is the case with older blood, said Dr. Susan Shurin, deputy director of the National Heart, Lung, and Blood Institute.
The six-week expiration date, specialists said, reflects a variety of biological considerations, as well as the vagaries of blood supply and demand. For example, Shurin said, the longer blood is stored, the greater the prospect that bacteria multiply, even during refrigeration. Those concerns, she said, become sufficiently worrisome by six weeks to restrict use of blood.
Each year, more than 14 million units of blood are given to patients in the United States. To manage supplies and avoid having to throw any of it out, blood banks typically distribute the oldest blood first. Doctors already try to minimize transfusions during surgery by, among other things, conserving, cleaning, and returning a patient's own blood.
The Cleveland Clinic scientists focused on patients undergoing heart surgery, a group that consumes a substantial share of the nation's blood supply.
The researchers followed patients who had surgery between June 1998 and January 2006, noting - but not controlling - the age of the blood they received. About 3,100 got blood stored for more than 14 days, while nearly 2,900 got the fresher blood. Nationally, among heart surgery patients who need transfusions, half get blood stored for 15 days or longer.
The scientists hunted for other factors that might have explained why the patients who got older blood fared worse, but the more they looked, the more they returned to the age of the blood as the probable culprit.
To be sure, the vast majority of heart surgery patients were still alive after one year, regardless of what type of blood they got. Still, there was a statistically significant difference: Nearly 93 percent of patients who got the fresher blood were alive, compared with 89 percent of those whose donated blood was older than two weeks.
Similarly, the patients getting older blood were more likely to suffer kidney failure (2.7 percent versus 1.6 percent) and serious infections (4 percent versus 2.8 percent). "I have to say," Koch said, "I wasn't entirely surprised."
Dr. Richard Benjamin, chief medical officer at the American Red Cross's national headquarters, described the study as "provocative . . . it certainly shows quite a strong result."
But, he said, the report falls short of being definitive because it does not represent what scientists consider the gold standard of research: a randomized clinical trial. In such a study, researchers in advance would divide patients into a group that, in this case, would get newer blood and a second group that gets older blood.
Until such a study is completed, Benjamin said, it's too soon to alter policy on blood use.
"We struggle every day to gather enough blood to meet the country's need," said Benjamin. "Any recommendation that suggests that we should not use some of the blood that we collect today is going to exacerbate those shortages."
The Food and Drug Administration, which establishes the nation's blood-use policy, expressed a similar sentiment in an e-mailed statement, saying that "while physicians may wish to consider these findings in making treatment decisions, regulatory actions are premature pending availability of more definitive scientific information."
Specialists said the findings regarding heart patients are not necessarily applicable to other people needing transfusions. That's because patients with cardiac conditions tend to be older and suffer a constellation of health problems. In contrast, an otherwise healthy patient who needs a transfusion to treat, say, anemia might do fine with blood that has been sitting around longer.
That suggests there may be a better way to manage the nation's blood supply - giving the freshest blood to those who would benefit most - according to an editorial accompanying the study and specialists, who said they were unaware of any hospital routinely doing this.
"The question is, are you getting as much bang for the buck as you could and in what circumstances do you need more bang for the buck?" Shurin said. "Someone whose organ system is on the brink may have much more need for a red blood cell that's in the prime of its life as opposed to a red blood cell that's been through the mill a little bit more."
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