Haemoglobin-based blood substitutes: what's on the horizon?

Military and civilian medical organisations have long recognised that an oxygen-carrying volume expander which is easy to store, transport and administer could be life-saving for trauma victims. Concern over fatal blood-borne pathogens including hepatitis and human immunodeficiency virus (HIV), as well as a shrinking donor pool further highlight the need for such a product. A variety of substances that transport oxygen and augment intravascular volume in the absence of red cells are emerging as possible "blood substitutes" for use in humans. These include haemoglobin solutions, liposome encapsulated haemoglobin (LEH) and perfluorocarbons. The purpose of this review is to discuss issues related to the various oxygen-carrying volume-expanding solutions by addressing the following questions: 1) What are the ideal properties of an oxygen-carrying volume expander? 2) What types of oxygen-carrying solutions are under development? 3) How does the efficacy of these compounds compare to their limitations and side effects? and 4) What are the potential clinical applications of these products?