to red cells, but we have heard earlier that it is hard enough to show that red cells work.
People are therefore looking for some sort of useful or practical benefit to an organ or to an organism. One possibility is showing that you can decrease allogeneic blood transfusions. Even though we know that the risk of allogeneic transfusion is very low, that might be something that could be considered of benefit and could support approval of such products.
In order to make these demonstrations of efficacy a bit easier, people are looking at different levels of use, localized perfusion, hypovolemic shock, and perioperative hemodilution, trying to go one at a time rather than get approval for all indications at once.
In conclusion, a red cell substitute appears feasible. There has been an enormous amount of research done in the past several years, and major advances have been made. However, progress has been slow. There have been toxicities, and there is still a lack of fundamental information. There was not the same enormous investment in all areas of basic research in the 1970s as there was in the molecular biology that spawned the biotech industry. When the AIDS crisis gave new stimulus to the development of blood substitutes in the 1980s, there was a large infusion of industrial activity.
The military has been interested in red cell substitutes since the late 1970s or early 1980s and has been the mainstay of support for research. Nevertheless, it remains difficult to demonstrate efficacy. The nature of a successful product is going to depend upon the results of our future research, and it may well be that a successful product will be part of an overall approach to the avoidance of allogeneic transfusion.