Oxygen Carriers in Cardiac Surgery

Abstract

SUMMARYArtificial oxygen carriers – the hemoglobin‐based oxygen carriers (HBOCs) and the perfluorocarbon (PFC) emulsions – have been developed with the aim of avoiding the risks associated with allogeneic blood transfusions. H BOCs are solutions of free human or bovine hemoglobin, modified by internal crosslinking and by polymerization so as to avoid renal toxicity and to increase the intravascular lifetime. Last‐generation PFC emulsions are formed by lipid particles enclosing a synthetic hyperfluorinated, chemically inert hydrocarbon, perflubron, which dissolves gases without binding them. In order to be efficient, the emulsions must be used with 100% oxygen.HBOCs and PFC emulsions were found to be safe and to reduce allogeneic blood transfusions in preclinical and clinical phase I/II studies. One PFC emulsion (Oxygent®) and three H BOCs (DCLHb, Hemolink® and Hemopure®) were used in phase II and III clinical trials in cardiac surgery with cardiopulmonary bypass (CPB). HBOCs were well tolerated but increased the number of adverse events, mainly hypertension, jaundice‐like syndrome and elevation of the blood levels of hepatic and pancreatic enzymes. The effects of HBOCs on transfusion avoidance were modest, limited to the first postoperative days, without decreasing the total number of transfused red blood cell (RBC) units. Oxygent® was used in combination with acute normovolemic hemodilution in phase II studies. It was safe, had modest effects on transfusion avoidance in the post‐CPB period (until 5 days for the highest administered dose), but did not decrease the number of allogeneic red blood cell units transfused per patient. A phase III clinical trial was voluntarily stopped before completion because of an increased incidence of adverse events (stroke). More evidence is warranted before oxygen carriers can be recommended for routine use in cardiac surgery.