Older Transfused Blood May Raise Risks After Surgery
Units near the 42-day storage limit could boost heart patients' chances of death, study finds
THURSDAY, June 22, 2006 (HealthDay News) -- When it comes to blood transfused during surgery into very sick heart patients, newer may be better, researchers report.
"High-risk patients who received older blood were more likely to die after cardiac surgery," said lead investigator Dr. Elliot Bennett-Guerrero, director of perioperative clinical research at the Duke University Medical Center.
Specifically, repeat bypass patients who received the "freshest" blood during their operation (stored for one to 19 days) had a 4 percent in-hospital death rate, compared to a 25 percent rate in similar patients receiving the "oldest" blood (stored for 31 to 42 days). U.S. Food and Drug Administration regulations prohibit the use of blood stored for more than 42 days.
The study authors and others stressed that blood transfusion is often absolutely necessary to save lives. They also noted that for healthier patients requiring fewer units of blood, any increase in risk from receiving older blood would probably be minimal.
The study appears in the July issue of Analgesia & Anesthesia.
Each year, Americans receive more than 12 million units of potentially life-saving blood, with more than 2 million units used in cardiovascular surgeries, according to data included in the study.
Whether or not the amount of time blood has spent in storage can affect the recipient's health "has been an age-old question in transfusion medicine," Bennett-Guerrero said.
In the new study, the Duke team took a retrospective look at the medical files of 321 patients who underwent repeat, open-heart surgeries for either coronary artery bypass or valve replacement between 1995 and 2001. The patients received a relatively large amount of donated blood -- an average of 5 units -- during these procedures.
The researchers tracked the patients' incidence of in-hospital and long-term mortality, as well as post-surgical complications such as kidney failure. They compared the rate of those types of outcomes to the number of units and age of the blood each patient received.
In-hospital death rates rose along with the age of blood received, the study found, as did hospital length-of-stay -- an average of 3.5 days for those receiving freshest blood vs. seven days for those getting older units.
Patients who received older blood also had higher rates of death in the eight years after their surgery, the researchers noted. According to Bennett-Guerrero, that's probably due to the long-term consequences of complications sustained just after surgery (for example, kidney failure) that may have been triggered -- at least in part -- by the use of older transfused blood.
Why might blood stored closer to the 42-day maximum be less healthy than "younger" blood?
"One of the theories is that as red blood cells age during storage, they become stiffer," Bennett-Guerrero said. "There's lots of evidence that these stiffer red blood cells may not deliver oxygen as efficiently. Or, they may even clot up or get stuck in organs and cause those organs to become damaged."
One blood expert called the study "commendable" but urged caution in interpreting the results.
"This paper is provocative, but it's a retrospective study with lots of confounding factors," said Dr. Richard Benjamin, chief medical officer of the American Red Cross. "We need to do a randomized, prospective trial to see if what we think we are seeing here is real."
Benjamin noted that the study focused on the very sickest type of patients, whose surgeries required very large amount of blood. The average "low-risk" patient might require just one or two units, he said.
"Remember, the more blood that you get, the more likely you are to get at least one old unit," Benjamin said. He added that the patients in the Duke study were already fragile; it's likely that healthier individuals wouldn't be at any significant risk from receiving a unit of older blood. "The danger [to that group] is infinitesimally small," Benjamin said.
And he said that, until supplies of donated blood increase, the only alternative is for patients is to receive "no blood at all."
"Our difficulty at the Red Cross is that we'd love to give everyone fresh blood -- there's no question about that," Benjamin said. "But we can't because there just isn't enough of it. So, we have to keep it on the shelf for a while. If we restricted its use to fresh blood only, a lot of people wouldn't get transfused, and they'd die."
Bennett-Guerrero agreed that a larger, prospective trial is needed, and said his team is applying for a U.S. National Institutes of Health grant to conduct just such a trial. If the results of that trial are similar to those found in the retrospective study, they may point to a need for more selective rationing of fresher blood to specific patients on a case-by-case basis, he said.
Bennett-Guerrero also seconded the notion that older, sicker patients may be at highest risk from receiving older blood.
"If you look at patients who are doing really well, maybe at lower risk for surgical procedures, my guess is that in that setting, it doesn't matter whether they even receive the blood or not, or whether the blood is older," he said. "But if you take someone who is 80 years old with complex heart surgery, who's already at high risk of developing complications, it may be a factor that puts them over the edge."
Find out how you can donate blood at the American Red Cross.