Stored Blood May Lack Vital Component
Tuesday, October 9, 2007
Much of the stored blood given to millions of people every year may lack a component vital for it to deliver oxygen to the tissues.
Nitric oxide, which helps keep blood vessels open, begins breaking down as soon as blood goes into storage, two research teams report in separate studies in this week's online edition of Proceedings of the National Academy of Sciences.
Doctors have become increasingly concerned about the numbers of heart attacks and strokes in patients receiving transfusions, and the new findings may help explain that. Red blood cells rely on opened blood vessels to deliver oxygen.
"If the blood vessels cannot open, the red blood cells back up in the vessel and tissues go without oxygen. The result can be a heart attack or even death," said Jonathan Stamler of Duke University, who led one of the research teams.
Currently blood is allowed to be kept in blood banks for up to 42 days. After that, it must be discarded. An estimated 14 million units of red blood cells are administered annually.
"We were surprised at how quickly [banked] blood changes -- we saw clear indications of nitric oxide depletion within the first three hours," Timothy McMahon, also of Duke and the leader of the other research group, said in a statement.
Researchers found that if they added nitric oxide to banked or stored blood at any point, the red blood cells were again able to open blood vessels and deliver oxygen to tissues, they said. They tested the blood with added nitric oxide both in the laboratory and in dogs.
Several of the researchers have consulting and/or equity relationships with Nitrox/N30, a company developing therapies based on nitric oxide.
"This is an important observation, and it needs to be followed up," said Louis Katz, a past president of America's Blood Centers, which provides about half the nation's blood. "It needs to be proven that it's clinically relevant."