The term "
blood substitute" is commonly misused when "
red cell substitute" is meant. The ideal
red cell substitute should deliver
oxygen (O2), require no compatibility testing, cause few side effects, have prolonged storage qualities, persist in the circulation, and be available at reasonable cost. While no
drug with all of these qualities is on the near horizon, several early generation
red cell substitutes are approaching submission for licensure, at least for limited indications.
Hemoglobin-derived
red cell substitutes from human bovine and recombinant sources, as well as perfluorochemicals that dissolve O2, are in different stages of development. While each formulation has its own physical characteristics,
biologic activities, and adverse reaction profile, all share one characteristic: The physiologic consequences of delivering O2 with small molecules is poorly understood, both accounting for problems seen in the clinical trials and providing therapeutic opportunities for the
cancer patient. All the
red cell substitutes in phase II trials have a life measured in hours and are unlikely to replace transfusions or drugs that stimulate erythropoiesis for chronic
anemia, but they may play a role in
cancer surgery, or even in
radiation therapy, or in the management of
cancer-related vascular occlusive syndromes.