newsobserver.com | Blood puzzle may be solved
Blood puzzle may be solved
Duke data could aid transfusions
Jean P. Fisher, Staff Writer
For years physicians noticed that patients who received transfusions of banked blood were more likely to die than those who got no blood. Now Duke University researchers think they know why -- and how the problem may be solved.
Donated blood almost immediately begins to lose a key gas that opens up vessels so oxygen and nutrients get to starved tissues, the Duke researchers report. Without that gas -- nitric oxide -- the vessels stay closed, blood can't deliver its precious cargo, and patients founder, the scientists suggest in two articles published online late Monday in the journal Proceedings of the National Academy of Sciences.
The good news is that nitric oxide can easily be put back into banked blood, restoring its ability to open vessels and transfer oxygen, the Duke scientists also report. Tests showed that blood replenished with nitric oxide successfully opened blood vessels in live dogs, doubling the flow of blood to the animals' hearts.
If similar results can be produced in humans, the findings could have huge consequences for the way donated blood is transfused.
Dr. Jonathan Stamler, a Duke physician trained in both cardiology and pulmonology and senior author of one of the recent articles, thinks replenishing blood before transfusion -- something that could be done in minutes by hospital staff -- could eventually become standard procedure. About 14 million units of donated blood are given to nearly 5 million Americans each year.
"There's a real hope that this can change practice," said Stamler.
The American Red Cross, the nation's largest supplier of banked blood, indicated that the Duke findings are of "considerable interest."
"We anticipate it may eventually lead to a better understanding of how to preserve red cell properties during storage," the Red Cross said in a statement.
Doctors unconnected to the Duke studies agree that there's a worrisome relationship between transfusion and poor patient outcomes, which has been demonstrated in studies over the past decade. But they say a lot more research is needed before depleted nitric oxide can be confirmed as the main culprit.
The reasons patients who get transfusions do worse "aren't well understood," said Dr. Mark Brecher, director of transfusion medicine at UNC Hospitals in Chapel Hill. Still, he thinks the Duke researchers have opened an intriguing new area of research.
"But I think it is just part of the answer," Brecher said. "They do not explain all of the questions about banked blood."
It has long been understood that banked blood undergoes many biological changes that may affect patients. Stamler's lab first described nitric oxide's role in dilating blood vessels years ago.
But the Duke studies are the first to document the rapid loss of nitric oxide in banked blood. One study found levels of the gas begin falling within three hours of donation and plummet 70 percent within 24 hours. That suggests a link to bad outcomes.
Stamler, who led the study that tested banked blood in dogs, agreed that studies in people are needed to determine the true clinical benefit. His study looked only at how well blood with both normal and depleted levels of nitric oxide opened blood vessels. It did not look at whether opening those vessels resulted in a better clinical outcome.
Without that information, it's hard to say what the findings really mean for patients, said Dr. Pascal "Osi" Udekwu, medical director of trauma and general surgery at WakeMed in Raleigh. Many transfusions are given either to surgical patients or those injured in accidents.
"This would be really important if they could show us an improved outcome," Udekwu, who is also an associate professor of surgery at UNC-Chapel Hill, said of the Duke studies. "But they have not shown that correction of this single problem will make blood use any safer."
Blood transfusion was once unquestioningly accepted as beneficial or even life-saving for patients whose blood levels drop, starving their tissues for oxygen. But that has changed over the past several years as research established a link between transfusion and increased risk for heart attack, heart failure and even death. One analysis of heart patients, published by Duke cardiologists, found that patients who had blood transfusions were about three times as likely to suffer a heart attack or die within 30 days as patients who did not have a transfusion.
Such findings initially caused physicians to speculate that problems in transfused patients might be unrelated to blood, stemming instead from the fact that they were already very ill. But the link between transfused blood and increased risk of death has since been established.
"It's something that we struggle with in medicine that no one knows about -- it's just not in the public domain," Stamler said. "We give millions of units, and we don't have a good idea of who we're benefiting."
He hopes his research can help find more answers.
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