It’s hard to argue with blood transfusions. Each year, nearly 5 million Americans receive them, and for many patients it’s a definitively life-saving therapy.There is, of course, a risk in transmitting diseases like hepatitis and HIV through transfusion, but modern operations can all but eliminate that threat. Curiously, however, there have been persistent observations about another problem with blood transfusion: In some settings, blood transfusions worked less effectively than expected, but no one knew exactly why. Now two groups at Duke University may have found the reason: the loss of the molecule nitric oxide from stored blood.
Nitric oxide is one of those "big" molecules. Its first biological effects were described in the 1970s, and in the 1980s it was determined that the gas contributes to the normal dilation of blood vessels. This led to an avalanche of research, a 1998 Nobel Prize for its discoverers, and, most famously, the creation of Viagra. (For those of you who are wondering, nitric oxide is not laughing gas. That’s nitrous oxide. Mixing up the two could presumably cause some very undesired results.)
In papers published in the Proceedings of the National Academy of Sciences, two teams at Duke showed that the nitric oxide normally found in red blood cells disappeared within a few hours of the blood being processed for transfusion. When animals in lab studies received transfusions of the nitric oxide–depleted blood, their blood vessels did not dilate to normal levels, decreasing the amount of blood—and oxygen—that gets delivered to muscle and other tissue. Replacing the nitric oxide, a relatively simple procedure, made the transfused blood effective at expanding blood vessels and delivering more oxygen.
This is the kind of study everyone likes. It answers a question that has been bothering people for a long time, the answer makes sense, and the potential solution is straightforward. If this work can be duplicated in other animals and then in humans, it could go a long way toward making blood transfusions a safer and more effective option for patients who need them.
Robert W. Lash, M.D. is an associate professor of internal medicine at the University of Michigan Medical School. His clinical interests include thyroid disease, diabetes, endocrine disorders in pregnancy, osteoporosis and metabolic bone disease, and medical education. A member of the LLuminari team of experts, a board certified internist and endocrinologist, Dr. Lash has an active clinical practice and is a hospitalist at the University of Michigan.
