Scientist foresees blood substitute for transfusions

March 14, 1993|By Jonathan Bor | Jonathan Bor,Staff Writer

A substitute for blood that could be used in transfusions without risk of hepatitis or HIV infection could be available within five years, a federal scientist predicted yesterday.

"Blood is safer today that it ever was before by several orders of magnitude," Dr. Harvey G. Klein, director of transfusion medicine for the National Institutes of Health, said at a trauma symposium in downtown Baltimore.

"But the public won't be satisfied until there is zero risk."

Dr. Klein said the best prospect is a synthetic hemoglobin, brewed in vats containing yeast or bacteria. He tempered his enthusiasm by saying he is a consultant to Somatogen, a private company in Boulder, Colo., that is testing such a product on humans.

Hemoglobin, the pigment in red blood cells, is the molecule that transports oxygen to tissues throughout the body. In experiments, the substitute is being produced by yeast and bacteria that have been altered to carry the human gene for hemoglobin.

Another possibility is natural hemoglobin extracted from human blood, then sterilized to destroy any infection. The product also would have to be chemically altered to keep it from breaking down once it enters the bloodstream and to enhance its ability to deliver oxygen to tissues.

Dr. Klein spoke at the 15th annual National Trauma Symposium, sponsored by the Maryland Institute for Emergency Medical Services Systems. The three-day conference, which concludes today, drew 300 doctors and nurses from the United

States and such countries as Brazil, Iceland, Germany and Austria.

Human trials are being conducted by a host of private companies, some of which are expected to report early results next week at an international meeting in San Diego.

So far, small doses have been given to healthy people -- no one facing surgery -- in tests to measure safety.

If the products prove safe, more trials will judge their effectiveness in patients undergoing surgery. An effective substitute is one that survives sterilization, persists in the bloodstream without falling apart, and delivers oxygen to tissues without causing infection or allergic reactions.

The next phase of experimentation could involve Jehovah's Witnesses, who object to blood transfusions for religious reasons but might

agree to substitutes. Dr. Klein said some church officials have deemed the synthetic products acceptable.

Other candidates could include surgery patients who cannot accept transfusions because their immune systems are armed to reject anyone's blood but their own.

Although screening techniques have greatly enhanced the safety of the blood supply, Dr. Klein said, transfusions still carry a small but real risk of infection.

The odds of contracting viral hepatitis from a single unit of blood are about 1 in 3,000, while the chance of contracting HIV, the virus that causes AIDS, are about 1 in 225,000.

Even with such long odds, "We expect 200 to 400 cases of HIV transfusion by blood each year," Dr. Klein said.

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