Studies Probe Weaknesses in Donated Blood

MONDAY, Oct. 8 (HealthDay News) -- Researchers have spotted a chemical deficiency that renders donated blood stored in blood banks less effective at delivering oxygen to tissues, compared to fresh blood.

But in a second study, the same group of scientists may have also found a way to remedy the problem.

Though unlikely to change current clinical practice in the short term, the findings help explain why, in many cases, blood transfusions do more harm than good by boosting risks for heart attack, organ failure and even death, experts say.

The studies "reinforce that conservatism [in giving transfusions] is important," said Dr. Louis Katz, executive vice president for medical affairs at the Mississippi Valley Regional Blood Center in Davenport, Iowa, and past president of America's Blood Centers, a network of community blood banks. "First, do no harm -- don't transfuse unless you must," he said. Katz was not involved in either study.

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Both reports were published this week in the early online edition of the Proceedings of the National Academy of Sciences.

Drs. Jonathan Stamler and Timothy McMahon, of Duke University Medical Center in Durham, N.C., led separate research teams that independently examined the ability of fresh and banked human blood to serve its medical purpose -- to increase oxygen availability to tissues that need it.

This activity is based on two parameters -- how much oxygen, and how much nitric oxide the red blood cells hold. Nitric oxide (NO) is a vasodilator -- a compound that opens (dilates) blood vessels. It is carried in red blood cells by hemoglobin, the oxygen-delivering protein that gives red blood cells their color. When hemoglobin encounters a tissue with relatively little oxygen, it releases NO, thereby causing blood vessels to open and ease the red cells' entry into the tissue, where they can release their oxygen.

Stamler and McMahon (previously a research fellow in Stamler's lab) found that stored blood rapidly loses the bulk of its NO within three hours of collection. Its ability to induce vasodilation likewise diminishes, they said.