Age of Transfused Blood May Play Part in Recovery
By NICHOLAS BAKALAR
Transfusions with blood that has been stored for long periods of time may decrease the survival rates for seriously ill surgery patients, a new report suggests.
In a study of patients undergoing repeat heart surgery, researchers found that the risk of premature death, both in the hospital and long-term, increased significantly with each day the transfused blood had been stored. Food and xxx Administration regulations allow the refrigerated storage of liquid blood for 42 days.
Red blood cells, the authors write, undergo significant changes during storage, including an increase in abnormally shaped red blood cells that may impair oxygen delivery to tissues.
But the clinical significance of the changes is not clear. In a retrospective study of 321 heart surgery patients, the scientists found that the rate of in-hospital death increased by 8.5 percent and out-of-hospital death by 10 percent for each additional day the transfused blood had been on the shelf.
“According to the F.D.A., 42-day-old blood is just as safe and effective as 10-day-old blood,” said Dr. Elliott Bennett-Guerrero, the lead author on the study and an associate professor of anesthesiology at Duke University. “But we are concerned that one reason why some studies show blood transfusions to be detrimental may relate to the age of the blood.”
Rates of in-hospital mortality ranged from about 4 percent among patients who received the “newest” blood (1 to 19 days old) to 25 percent among those who received blood that had been stored for 31 to 42 days. Blood older than 42 days is discarded.
Although the retrospective nature of the study, which appears in the July issue of the journal Anesthesia & Analgesia, prevented the scientists from determining the exact mechanism at work, they were able to track kidney failure as one effect.
Transfusions with older blood were a significant predictor of post-operative kidney function. The patients who received blood stored for less than 20 days had about an 8 percent rate of acute renal dysfunction, while those who received blood stored more than a month had an almost 50 percent rate of kidney failure.
The length of hospital stay also went up consistently with the age of the blood used.
People who received blood less than 20 days old averaged about 12 days in the hospital; those who received blood older than one month had an average stay of about 18 days, including twice as much time spent in the intensive care unit.
The correlations held even after adjusting for xxx, obesity, type of surgery, number of transfusions and other variables.
“If you’re getting one unit of blood,” Dr. Bennett-Guerrero said, “it probably doesn’t matter much whether it’s older or fresher. But if you’re getting six or eight units of blood, it might matter more whether that blood is old.”
The question of aging blood has been around for decades, Dr. Bennett-Guerrero said.
“The main standard the F.D.A. uses is that 75 percent of transfused blood cells have to be in circulation 24 hours after the transfusion,” Dr. Bennett-Guerrero said. “That’s why blood has a shelf life of 42 days. But there have been no trials to determine if this older blood helps patients or is harmful.”
The average age of most transfused blood, Dr. Bennett-Guerrero said, is about two to three weeks.
“It’s important to donate blood,” he added. “The more people who donate blood, the more that’s in the system, and the more flexibility blood banks have to administer fresher blood to patients.”
Still, he said, he is not suggesting that current practice should be changed on the basis of this study.
“It is one more piece of evidence,” he said, “that might suggest to clinicians that transfusing blood may not always be benign.”
Dr. Bennett-Guerrero emphasized that a large randomized trial would be required before any firm conclusions could be drawn.
“We don’t know for sure that older blood is bad for you,” he said. “But we really need to know the answer, one way or the other.”