Red cell substitutes are solutions that can potentially be used in emergencies or during surgery when rapid expansion of the blood volume with an oxygen carrier is needed. The three main types of products being developed in research and commercial laboratories are those based on cell-free hemoglobin, perfluorocarbon emulsions, and liposome-encapsulated hemoglobin. No product is currently approved for clinical use, but a number of hemoglobin-based products are in advanced clinical trials and approval could come as soon as the next 1-2 years. Outside the red blood cell, hemoglobin is subject to degradation and heme loss, it readily diffuses in the plasma space and effectively scavenges nitric oxide. Thus the major limitation to cell-free hemoglobin products has been vasoconstriction, a biological effect that offsets the desired oxygen transport. The physiological effects of these solutions must be under-stood and controlled in order for hemoglobin-based products to fulfill their promise. An exciting consequence of the development of red cell substitutes has been a deeper insight into the way in which oxygen is delivered to tissues in the microcirculation and how blood flow distribution is regulated within and between organs. This insight will lead to more rationally designed second generation products. In coming years, it is expected that clinical applications for red cell substitutes will expand as experience with them grows and products with a range of properties become available to clinicians and scientists.
Mots clés substituts de sang, transport d'oxygène, physiopathologie, effets secondaires.