Blood transfusions often kill the patients they are meant to help. For years, it has been known that patients who receive donated blood run a much higher risk of dying from heart attacks and other cardiac problems in the weeks following their blood transfusion. Now, some researchers believe that these problems stem from the fact that stored blood lacks nitric oxide, a vital component that helps it function properly.
Studies have shown that patients receiving donated blood during a transfusion meant to restore oxygen to dying tissue run a 25% chance of having a heart attack and an 8% chance of dying within a month of the blood transfusion. Similar patients only run an 8% risk of having a heart attack and a 3% risk of dying in the same time period. The statistics are similar for all patients receiving blood transfusions with stored blood, whether they are trauma victims, have suffered from heart attacks or anemia, or are undergoing chemotherapy. But unfortunately, doctors have had no choice but to take their chances with stored blood, as compatible fresh blood is a scarce commodity, especially in emergency situations.
Finally, some researchers at the Duke University Medical Center believe they have discovered the problem with stored blood. According to an article published earlier this month in the Proceedings of the National Academy of Sciences, stored blood begins losing nitric oxide almost as soon as it is donated. Blood cannot function properly without nitric oxide, because this gas helps the blood deliver vital nutrients to tissue. It does this by taking oxygen to tissue, and by opening tiny blood vessels in the body so that blood can flow more easily. According to the Duke study, within a scant 42 days of donation, most of the nitric oxide that was once in stored blood has expired.
Basically, patients who receive old, stored blood are getting something that is going to do them more harm than good. The Duke scientist reasoned that without nitric oxide, red blood cells have no way to enter the body’s tiniest blood vessels. So they pile up, and actually block blood flow to the heart. As a result, this nitric oxide deprivation can ultimately lead to heart attacks and other heart problems, and quite possibly death.
Already, these new findings are inspiring changes in the way doctors approach blood transfusions. Traditionally, a blood transfusion was considered if the level of a patient’s red blood cells – called hematocrit – dropped below the normal range of 45% to 50%. But now, some physicians wait until hematocrit levels are below 30% before ordering a blood transfusion. By doing this, patients can often be spared a potentially fatal blood transfusion.
But the Duke researchers have proposed another solution to the blood transfusion problem that could save thousands of lives every year. They say experiments with mice have shown that replacing the depleted nitric oxide in stored blood will return it to full effectiveness. And they believe this would work with humans as well.
Unfortunately, these new findings have not been enough to persuade blood suppliers to change how they process and store donated blood. The American Red Cross, by far the country’s largest supplier of donated blood, says that it wants to wait for other studies to confirm Duke’s findings before it makes changes. In the meantime, doctors will have no choice but to continue weighing the risks and benefits of blood transfusions for some of their sickest patients.
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