Blood Substitute Tested

Blood Substitute Tested

According to medical lore, the ancient Incas were the first to attempt blood transfusions. And over the centuries doctors around the world have pumped everything from beer to urine into hemorrhaging patients. Now, surgeons across Canada are pushing back the frontiers of transfusion science even more with an innovative blood substitute. Hemolink, which duplicates blood's life-saving, oxygen-carrying capacity, was tested on patients undergoing hip and knee replacement surgery. This week, a patient about to undergo heart surgery is scheduled to use Hemolink, the first of a group of heart patients in the final phase of the trial. The attraction is obvious, says Dr. Sheldon Tobe, a kidney specialist at Toronto's Sunnybrook Health Science Centre who would like to use Hemolink for kidney dialysis: "Our patients won't have to use as much donated blood."

With Canadians wary of contaminated blood and donations plummeting from 1.17 million units in 1990 to 880,000 last year, blood replacements are expected to be widely used. Indeed, industry forecasters predict a $7.6-billion North American market within a few years. The substitute lasts about 36 hours in humans - long enough for the body to begin reproducing its own blood. Products like Hemolink, which is manufactured by Toronto-based Hemosol Inc., will not only help keep blood supplies up - particularly in emergency rooms - they will also enable paramedics to deliver transfusions in the field more easily because the substitute blood is compatible with every blood type. Even more important: for the first time patients will be transfused with a substance that is absolutely free of potentially deadly viruses. Says Michael Gross, an associate professor of surgery at Dalhousie University who used Hemolink during operations in Halifax: "Most people still don't like the risk associated with a normal blood transfusion. Blood is not 100 per cent safe. Nothing is."

Two other leading U.S. firms, Northfield Laboratories Inc. of Evanston, Ill., and Biopure Corp. of Boston, are also trying to beat Hemosol to market with mock blood. Initial studies, published this month in the Journal of the American College of Surgeons, are encouraging. So much so that the U.S. Food and Drug Authority last week called for much wider tests, prompting company executives to predict they could be approved for general use within the next two years. Dr. John Marshall, director of research at Toronto Hospital's intensive-care unit, said the impact of artificial blood could be dramatic. "If we had a fluid that would carry oxygen," said Marshall, "that would be a very significant step forward."

Getting to market, however, is no sure thing. On June 2, after spending more than $456 million on research, Baxter Healthcare Corp. of Deerfield, Ill., which also attempted to create a hemoglobin-based blood, cancelled its program after complications arose in some severely ill patients. Only one other artificial oxygen carrier, Fluosol, a chemical developed by Green Cross Corp. in Japan in the 1970s, has been available. But it was withdrawn in 1994 for lack of use.

The drive to find an alternative to blood picked up speed following the contamination of the blood supply with the virus that causes AIDS. According to Hemosol president John Kennedy, the firm conducted two polls last winter that found that 30 per cent of respondents would rather have a substitute than donated blood and were willing to pay extra for it. Adds Kennedy: "The big gain is that we will be able to conserve donated blood for high-volume situations."

The mock blood is made from hemoglobin extracted from red blood cells in donated blood that has passed its 42-day shelf life. The cell membranes are opened up and the hemoglobin is extracted and run through microscopic filters to remove viruses. The blood is then reconstituted, enabling it to carry oxygen. In the future, blood replacements may become even more sophisticated. At McGill University in Montreal, biomedical engineer Thomas Chang is attempting to restore some of the enzymes that are stripped from the cells in the manufacturing process, making the substitutes more useful.

Red Cross officials, meanwhile, are not yet sure what impact artificial blood will have on the need for donations. Last year, 40,000 units of donated blood expired on the shelf and could have been used to make new blood products. But if the demand for virus-free substitute blood increases dramatically, companies producing artificial supplies might end up in competition with the Red Cross. "At this point, I think artificial blood will fill a well-defined niche," says Graham Sher, a medical director with the Red Cross in Toronto. "But I don't see the demand for donated blood decreasing." Whatever happens, the ancient science that began with the Incas is about to change dramatically.

Maclean's August 24, 1998