Blood substitutes

Risk of disease transmission and limitations in the ability to transfuse in the prehospital or combat setting have stimulated research in the field of oxygen therapeutics. Several products have completed safety trials and are presently undergoing investigation for their efficacy. In the near future, the clinician will likely employ these products in the management of a variety of patient populations. Though similar in their oxygen carrying capacity, each agent possesses distinct physiologic effects. Understanding of the benefits and shortcomings of the various compounds is essential in order to optimally utilize them in various clinical settings. This review provides an overview of recent developments in the field of oxygen therapeutics and highlights results of clinical trials.

Modified hemoglobin solutions of human or bovine origin and perfluorochemical-based emulsions are in advanced stages of clinical testing. Bovine hemoglobin-based solutions have been associated with vascular reactivity, methemoglobin formation and development of antibodies. Larger safety trials are necessary before they can find widespread use. Polymerized human hemoglobin solutions have a favorable safety profile in early trials and have been effective as a resuscitation fluid in circumstances when red cells may be unavailable. Unfortunately, outdated human blood, the substrate for this product, is itself in short supply. Perfluorocarbons similarly reduce the need for allogeneic transfusion, but the need for high-inspired oxygen levels currently limits use. Recombinant, polymer-encapsulated and additional forms of chemically modified hemoglobins are being developed and are undergoing testing in animal models

Oxygen carriers offer a viable alternative to allogeneic transfusion. All oxygen therapeutic agents are not clinically equivalent. Optimal utilization requires a thorough understanding of the therapeutic potentials and adverse effects of the solution being considered for use.