Researchers in the United States say one of the reasons why many patients do not do well after blood transfusions is because donated blood rapidly loses some of its life-saving properties.
The researchers at Duke University Medical Center in Durham, North Carolina, have found that nitric oxide in red blood cells is the key to transferring oxygen in the blood to tissues.
This important gas dissipates almost immediately after red blood cells leave the body and much of the blood stored in blood banks becomes impaired.
Blood delivers oxygen to tissues because of the presence of nitric oxide, which opens up vessels allowing blood cells to pass through, but according to the researchers if the blood lacks nitric oxide, oxygen will not enter into the tissues.
Duke researcher Dr. Jonathan Stamler says if the gas is restored the banked blood appears to regain this ability.
Dr. Stamler, the senior author of the report, says the medical community has been struggling with the issue of blood not being quite good enough for the last five to eight years and numerous studies have shown that patients who receive blood transfusions have higher incidents of heart attacks, heart failure, stroke and even death.
Dr. Stamler says the issue is not a new one and though researchers have known that banked blood is not the same as the blood in the body, the exact difference was unclear.
Stamler and his colleagues measured the levels of nitric oxide in stored human blood obtained from a commercial supplier and found that nitric oxide levels started dropping quickly.
They tested the theory on dogs and found that when they were given stored blood, the flow of oxygen-rich blood was impaired; but when nitric oxide was added back into stored blood, the blood flow was restored.
A second team led by Dr. Timothy McMahon documented the depletion of nitric oxide in banked blood and were surprised at how quickly the blood changes.
Dr. McMahon says they saw clear indications of nitric oxide depletion within the first three hours.
Both teams have called for clinical trials to study exactly who might benefit from banked blood and research into methods to safely add nitric oxide back into banked blood in order to see how this might improve its effectiveness.
Dr. Stamler says transfusions were important as they "could be life-saving" but there was "little doubt" transfused blood could be harmful.
According to the National Institutes of Health about 5 million Americans receive blood transfusions each year.
Both studies appear in the journal the Proceedings of the National Academy of Sciences.