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Artificial oxygen carriers are not blood substitutes. They serve to carry oxygen to tissues and are either hemoglobin based or perfluorocarbon based. Driving the development of artificial oxygen carriers are concerns involving both the safety and quantity of the blood supply. No artificial oxygen carriers are currently approved for clinical use in the United States. Hemopure has been approved for use in South Africa. The companies producing Hemopure and PolyHeme, both of which are hemoglobin-based oxygen carriers, have filed a Biologic License Application in the United States. Phase III trials have been completed for Hemopure, while PolyHeme is currently undergoing phase III trials in the PolyHeme Urban Ambulance Trial. No North American trials are under way for perfluorocarbons.
Key words: Artificial oxygen carriers, hemoglobin-based oxygen carriers, perfluorocarbon-based oxygen carriers.
Artificial oxygen carriers (AOCs) are synthetic solutions with the ability to bind, transport, and unload oxygen in the body.1,2 Some authors prefer the term oxygen therapeutics, which includes AOCs, for those agents designed to deliver oxygen to hypoxic tissues and organs.3,4 These compounds lack other components of blood, such as immune cells and coagulation factors. As such, "blood substitutes" does not accurately describe either their use or their function; thus, these agents are more properly called red blood cell (RBC) substitutes or those terms just described.3 The US Food and Drug Administration (FDA) must approve any AOC before its clinical use because these substances are considered drugs.
Types and uses of artificial oxygen carriers
* Types of artificial oxygen carriers. Two viable categories of AOCs currently exist: hemoglobin-based oxygen carriers (HBOCs) and perfluorocarbons (PFCs).1-9 Hemoglobin taken directly fromRBCs cannot be used as an intravascular oxygen carrier. To avoid spontaneous breakdown of hemoglobin and the toxicity of hemoglobin extracted from RBCs, HBOCs use purified human, animal (bovine), or recombinant hemoglobin as raw materials. The purified hemoglobin is then either altered chemically or microencapsulated.1-3,6,7,10-12 Perfluorocarbons are liquid fluorinated hydrocarbon compounds capable of carrying dissolved oxygen and delivering that oxygen under physiologic conditions. Theymust be sufficiently biocompatible to administer into the intravascular space. Perfluorocarbons require emulsification because they do not readily mix in aqueous systems such as blood.1-3,6,13
* Uses of AOCs. Artificial oxygen carriers have been developed for 2 major purposes. As bridge oxygenators, they function...