[Current research on oxygen carriers for transfusion: hemoglobin solutions and fluorocarbon emulsions]

Although products currently under study are usually called "artificial blood" or "blood substitutes", it concerns only, for the moment, to achieve preparations able to carry and release oxygen to tissues while allowing also a temporary restoration of "blood" volume. The most advanced scopes are related to hemoglobin solutions and fluorocarbons emulsions. The limitations of free hemoglobin impose to modify it. The reestablishment of a normal, even reduced, affinity for oxygen is obtained by the fixation on hemoglobin of a 2,3-DPG substitute whose most known example is pyridoxal phosphate. The enhancement of vascular retention may be achieved by intramolecular cross-linking, intermolecular polymerization or covalent binding of hemoglobin on macromolecules. The two modifications of hemoglobin must be performed successively et numerous possibilities have been proposed. Bovine and recombinant hemoglobins are also promising. Originally and logically, fluorocarbons are synthetic compounds derived from hydrocarbons by an important or maximal substitution of hydrogen by fluorine. The physical properties of these molecules, impose, for transfusion, their emulsification in an aqueous physiological solution. They need an oxygen enriched atmosphere and their storage in tissues is often extended. At present, the most known emulsion is Fluosol DA, a mixture of perfluorodecalin and perfluorotripropylamine. It allowed to realize numerous researches and the proposal of the multiple possible employment for this category of oxygen carriers. The limitations of Fluosol DA led to fluorocarbons under investigation such as F dimethyl bicyclononanes, F methyladamantane, bis (F-butyl) ethene or F-octylbromide. The new hemoglobin solutions and fluorocarbons emulsions start to meet the requirements of potential users.