Stale banked blood can have fatal repercussions

Blood transfusions are supposed to save your life, not hasten your demise. Yet recent evidence suggests that transfusions can increase your chance of heart attack or death. Now two separate teams have figured out why -- and suggested a way of turning things around.

In the United States, almost 14 million units of blood are dispensed each year to 4.8 million patients. The collection and processing of the blood is strictly regulated and huge efforts are made to keep it free of infectious agents.

But while blood transfusions undoubtedly save many lives, over the past five years, several studies have found that patients who received transfusions were also more likely to suffer heart attack, heart failure, stroke and death.

In 2004, for instance, a study of heart patients found that those given transfusions were more than twice as likely to die in their first 30 days after arriving at hospital and three times as likely to have a heart attack.

Paradoxically, while the main reason for giving a transfusion is to carry more oxygen to body tissues, researchers found that sometimes the opposite happens, and tissues become starved of oxygen. Now researchers think they know why.

In the U.S., red blood cells can be banked for up to 42 days at 4 degrees C. Some evidence suggested that the longer the blood was stored, the worse the outcome. So two separate teams of researchers from Duke University in North Carolina set out to investigate.

Jonathan Stamler's team tested blood that had been collected, processed and stored according to set standards, and found that within a single day, levels of nitric oxide -- an important signaling molecule in the body -- had dropped by 85 percent. Timothy McMahon's team found that blood was already depleted of the compound within three hours of collection.

Getting oxygen into a tissue is largely dependent on blood flow, and this is a carefully orchestrated process. Red blood cells can sense the level of oxygen in their immediate surroundings and, when levels are low, will release NO to open up blood vessels and allow more oxygenated blood to pass through.

However, banked blood that is lacking in NO fails to do this. Consequently, it cannot perform the most important job that transfused blood is supposed to do.

The good news is that NO can be put back into blood. By adding a solution of nitric oxide to red blood cells, Stamler was able to restore levels to those of fresh blood. What's more, when the fortified blood was transfused into dogs with too little oxygen in their blood, the NO-rich blood got significantly more oxygen to the animal's heart than the regular banked blood.

Stamler thinks that blood banks and doctors should work together to find a way to make this a standard procedure, though doing so would require approval from the U.S. Food and Drug Administration.