We recycle a lot of things -- paper, plastic, metal, blood.
A Johns Hopkins University study, published in the June issue of the journal Anesthesia and Analgesia, explains one reason for that. As banked blood sits on shelves for as long as 42 days, the membranes of red blood cells become less able to change shape and squeeze through the smallest capillaries to deliver critical oxygen to tissues.
"The smallest capillaries are five microns in diameter. Red blood cells are seven microns," said Steven Frank, an associate professor in the Department of Anesthesiology at the Johns Hopkins School of Medicine, who led the research. In addition to their weakened ability to deliver oxygen, the red blood cells can sometimes plug those capillaries, he said.
The irony is that blood banks sometimes face shortages of donated blood, and red blood cell salvaging, as it is sometimes known, is cheaper than using banked blood. Banked blood -- whether obtained from the Red Cross, a practice followed by smaller hospitals, or banked at major facilities such as Hopkins -- costs about $240 per unit, Frank said. Recycled blood costs about $120 for the plastic tubing and other equipment needed to salvage the first unit, but nothing more once the equipment is set up in an operating room and a person is brought in to run it.
Smaller hospitals may not have the equipment or personnel for such salvaging, but larger ones certainly do, Frank said. The technique, which can recapture 50 percent to 75 percent or more of a patient's blood, can be used during heart surgery, vascular surgery, joint replacements, transplants, some Caesarean sections and even trauma surgery, he said.
"We do use the cell-saver blood," Frank said. "I just think we don’t use it enough. The banked blood is the easy way out. It’s always available."
Recycling a patient's blood became popular in the 1980s, when the risk of HIV in donated blood was higher. But now banked blood is considered so safe that getting HIV or hepatitis from it carries the same risk as being struck by lightning or killed in an airplane crash, Frank said.
Five large studies have shown that the amount of blood needed doesn't affect the fresh vs. stored equation either, Frank said. In all of those studies, people receiving fresh blood were less likely, or no more likely, to suffer heart attacks, strokes, death or infections after surgery, he said.
In the Johns Hopkins study, researchers divided 32 patients into three groups. One received only recycled blood; one received mostly recycled blood supplemented by a small amount of banked blood; and one received recycled blood plus a larger amount of stored blood. The banked blood had been stored an average of 25 days.
The patients receiving banked blood did worse than those who received only their own recycled blood, the study showed, a condition that lasted for about three days after surgery.
"People say blood saves lives, and it does if you’re hemorrhaging," Frank said. But it's also "very clear that the longer they're stored in the blood bank, the less functional the red blood cells are."