Safety of Blood Supply

All U.S. blood banks have set up special procedures to make sure that the blood supply is safe. The U.S. Food and Drug Administration (FDA) makes sure that the 3.5 million people who have a blood transfusion each year are protected by five layers of safeguards:

1. Anyone who wants to donate blood must answer a series of questions about potential risks that could affect the safety of their blood. For example, people who have used intravenous drugs in the past are not allowed to donate blood. Trained personnel take a very detailed medical history and conduct a brief physical examination to make sure that the donation is safe for both the potential donor and the patient who receives the donated blood.

2. Collection centers use a new sterile needle to collect blood into a new, sterile bag. The donor’s arm is carefully cleaned before the needle is inserted. When a donor gives a pint of blood at a blood collection center, he or she also provides a few test tubes of blood. These test tubes are sent to a laboratory, where a trained technician does several tests on each sample. Specifically, the technician screens the blood for:

• Seven infectious diseases, such as hepatitis B, hepatitis C, syphilis (a sexually transmitted disease), human T-lymphotropic virus types I and II (which can lead to leukemia and other diseases), and human immunodeficiency virus (HIV)
• Red blood cell antibodies (proteins that attack foreign substances in the body) that could cause a transfusion reaction in certain people.

3. Blood banks are required to keep a list of donors who have not been allowed to donate in the past. They do not collect blood from these people.

4. Once a center collects blood, the blood bank does not use the donated blood until it has been tested and the test results show that it does not have any infectious agents. The period when the blood is not used is known as quarantine.

5. Blood centers are required to investigate any manufacturing problems in their equipment, correct any problems they find, and let the FDA know about these problems.

If any of these safeguards shows that donated blood might not be safe, the donated blood is labeled unsafe for transfusion and can be recalled.

Recent Research Results

In October 2007, researchers at Duke University published two studies on possible reasons for certain complications from blood transfusions in a medical journal (see Bennett-Guerrero E, Veldman TH, Doctor A, Telen MJ, Ortel TL, Reid TS, Mulherin MA, Zhu H, Buck RD, Califf RM, McMahon TJ. Evolution of adverse changes in stored RBCs. Proc Natl Acad Sci U S A. 2007 Oct 23;104(43):17063-8; Reynolds JD, Ahearn GS, Angelo M, Zhang J, Cobb F, Stamler JS. S-nitrosohemoglobin deficiency: a mechanism for loss of physiological activity in banked blood. Proc Natl Acad Sci U S A. 2007 Oct 23;104(43):17058-62) These scientists explained that when red blood cells are stored after they are donated, they lose some of their nitric oxide.

The hemoglobin in red blood cells delivers oxygen and carries nitric oxide, which dilates (opens) blood vessels. As the blood carries the hemoglobin throughout the body, the hemoglobin releases nitric oxide whenever it reaches a tissue without enough oxygen. The nitric oxide makes the blood vessels open. This lets the red blood cells enter the tissue and deliver their oxygen.

But once donated blood has been stored for even a few hours, it starts losing its nitric oxide. With less nitric oxide, the cells can’t deliver enough oxygen to the all the tissues in the body. This can lead to heart attacks, strokes, organ failure, or even death.

However, soaking the red blood cells in nitric oxide for a few seconds seems to fix the problem. The researchers suggest that replacing the nitric oxide that is lost in stored red blood cells could make blood transfusions more effective. However, more research is needed to make sure that reconstituting the nitric oxide in stored red blood cells is safe and effective.