Potential lifesaver
Thousands of accident and trauma victims bleed to death each year on the way to the hospital or in the emergency room.
Transfusions could save them, but to avoid life-threatening tissue rejection, their blood first must be tested to determine its type. That test requires hospital laboratory equipment and can take up to an hour.
A synthetic blood substitute, given at the scene, could keep body tissue alive while avoiding the potential of rejection -- possibly saving 10,000 lives annually. Although several such substitutes have been devised over the years, some have caused serious side effects, such as high blood pressure, while developers of others have simply run out of money.
Medical experts now think one product may make it through the developmental gantlet. Called PolyHeme, the product has been shown in early tests to be safe. It’s already being tested at trauma centers nationwide.
“This product is one of the most exciting things to come along in emergency medicine in the last 30 years,” says Dr. David B. Hoyt, chief of trauma medicine at UC San Diego.
If it proves effective, the artificial blood could save victims of car crashes, gunshot wounds and stabbings as well as soldiers wounded on the battlefield. Eventually it could be used in rural areas or developing countries, where blood supplies may be limited, and as a backup during natural disasters, which can exhaust inventories of stored blood.
The need is as great as the potential, experts say.
When trauma patients lose massive amounts of blood, their blood pressure drops perilously low, depriving vital organs of needed oxygen and greatly increasing the risk of death.
Patients currently are injected with an intravenous saltwater solution to restore blood pressure and prevent hemorrhagic shock, which is a sudden decline in blood volume that can lead to death. But the saline does not contain hemoglobin, which is carried in the red blood cells that contain tissue-nourishing oxygen. As a consequence, victims’ organs can shut down before doctors and nurses can get fully cross-matched compatible blood. Those who survive can suffer brain damage.
“This can be used to treat people before they suffer irreversible harm,” says Dr. Steven A. Gould, chief executive of Northfield Laboratories Inc. of Evanston, Ill., which makes PolyHeme.
PolyHeme is composed of red blood cells extracted from outdated human blood. (Donated blood has a shelf life of about 42 days.)
The hemoglobin protein is then chemically modified so that it is universally compatible and can be safely stored in an ambulance for up to 12 months.
Even its proponents acknowledge that PolyHeme is merely a stopgap measure, not a replacement for real blood. “That is the disadvantage of blood substitutes,” Hoyt says. “Patients do need real blood if they haven’t been able to make their own supply.” After about 24 hours, the body absorbs the chemically altered cells.
Still, early studies have been encouraging. In one 2002 study of 171 massively bleeding patients who were given PolyHeme, 75% survived at least 30 days, compared with 35.5% among a set of matched historical controls who did not receive blood for religious reasons.
In January, the company began a nationwide test in which paramedics will use the blood substitute on severely injured patients headed for 20 trauma centers. The study, which will eventually encompass 750 patients, should be completed in 2005. If all goes well, the synthetic blood product could be available within the next two years, says Gould, transforming the treatment of serious trauma.
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Other products in the pipeline
Historically, the development of artificial blood, which has been a goal of emergency medicine since the 1950s, has been marked by failure. Some products made capillaries collapse, cutting off blood supply to tissues, while others raised blood pressure.
However, two other blood substitutes, currently being tested for use during orthopedic surgery, could ultimately be used to save lives. “The idea behind these products is to reduce the amount of blood they have to transfuse,” says Keith Berman of Health Research Associates, a pharmaceutical consulting firm in Pasadena.
One, called Hemopure, is derived from bovine hemoglobin. Made by Biopure Corp. of Cambridge, Mass, the product is approved for surgical use in South Africa and recently completed the final phase of clinical trials in preparation for FDA approval.
Hemospan, which is made by Sangart Inc. of San Diego, isn’t quite as far along; it just completed a test in 20 orthopedic surgery patients in Sweden.
