Artificial Oxygen Carriers as Red Blood Cell Substitutes – Perfluorocarbons and Cell-Free Hemoglobin

Abstract

Forthcoming shortfall of blood products and persisting concerns about viral transmission and immunosuppressive side effects of allogeneic blood transfusion have reinforced the studies with alternative oxygen carriers in the last years. Modern perfluorochemicals and cell-free hemoglobin solutions can be applied without prior cross-matching and are now available as stable formulations with long shelf life. Both groups of oxygen carriers have shown their effectivity and tolerability in numerous animal studies. An emulsion of perflubron which has a 60% weight/volume relation is actually undergoing phase III studies with respect to its effectivity in augmented acute normovolemic hemodilution since it has been shown to reverse hemodynamic transfusion triggers. While clinical studies with human cross-linked hemoglobin (DCLHb) have been stopped last year because of the results of two clinical trials showing an increased mortality in patients with stroke and multiple injury shock being treated with DCLHb in comparison with saline, a phase III study with polymerized bovine hemoglobin HBOC-201 is actually being performed in noncardiac patients with perioperative bleeding. The objective of this multicenter study is to show that treatment with HBOC-201 can reduce or avoid allogeneic RBC transfusion. Besides its use in clinical transfusion protocols, artificial oxygen carriers have a unique potential to deliver oxygen to the tissues by plasmatic transport due to its different physiology of oxygenation when compared with conventional oxygenation provided by red blood cells. Future studies must show if these modern oxygen carriers are able to improve outcome of patients with impaired perfusion and organ oxygenation.