A safe, convenient alternative to human red blood cell (RBC) transfusion may one day become available. Oxygen therapeutics represents a potential new category of treatments that may replace blood transfusions. Oxygen therapeutic products deliver oxygen to tissues without having to transfuse blood, said Louis Katz, M.D., vp. for medical affairs, Mississippi Valley Regional Blood Center, Davenport, Iowa.
According to Katz, who is also chairman, Transfusion Transmitted Diseases Committee, American Association of Blood Banks, many reasons exist for developing a substitute for RBCs. He feels the public is most concerned about the transmission of bloodborne infections. He noted that the risk of transmission has become very small, however. A more relevant reason to consider oxygen therapeutics is the exacting requirements for obtaining, processing, and storing blood, he said.
The two major categories of oxygen therapeutics are hemoglobin-- based oxygen carriers (HBOCs), which can be made using either human or bovine hemoglobin, and perfluorocarbon-based products, said Katz. The manufacture and processing of these products should eliminate known pathogens, so they will not transmit infections, he added. HBCs and perfluorocarbons do not require compatibility testing and cross matching.
Both types of products are potentially suitable for long-term storage for months and perhaps years, Katz pointed out. He also said the products currently in clinical trials appear to be capable of reasonably and effectively delivering oxygen to the tissues.
Certain disadvantages to these products do exist, though, said Katz. If the product is derived from human hemoglobin, the supply of human hemoglobin is currently very limited, he said, adding that it generally requires two units of outdated human RBCs to make one unit of an oxygen therapeutic product. It is very expensive to outfit factories to produce HBOCs or perfluorocarbon-based products, he continued. Very large facilities are required.
Short-term use of HBOCs is associated with hypertension, cautioned Katz. Discoloration of the skin is also a potential adverse effect of HBOCs, said John W. Kennedy, M.Sc., president and CEO, Hemosol Inc., Ontario, Canada. This yellowing of the skin, which resembles a bruise, can occur when HBOCs are given at very high doses, he said. Skin discoloration occurs when the hemoglobin in the product, which is metabolized by the liver, becomes backlogged. …