D C Cheng1. 1. Department of Anesthesia, Toronto General Hospital, University of Toronto, Ontario, Canada. davy.cheng@uhn.on.ca
Abstract
PURPOSES: There are currently two major classes of oxygen therapeutics: hemoglobin based oxygen carriers (HBOCs) and synthetic perfluorocarbons (PFCs). This review focuses on the use of o-raffinose cross-linked human hemoglobin (Hb raffimer) in cardiac surgery. SOURCE: The literature on HBOCs was reviewed and the development and clinical trials on Hb raffimer were outlined. PRINCIPAL FINDING: The benefits of HBOCs include avoidance of known viruses, pathogens and cross-matching; increased stability and storage time; and efficient oxygen delivery to tissues. The limitations of HBOCs include binding the endogenous vasodilator, nitric oxide, thereby resulting in transient hypertension, esophageal dysfunction and abdominal discomfort. The short half-lives of these products makes them best suited to situations of acute anemia. Hb raffimer is prepared from outdated red blood cells, cross-linked with o-raffinose, a polyaldehyde obtained through the oxidation of the trisaccharide raffinose. The Hb is covalently cross-linked (beta-beta) within the 2,3 DPG binding pocket to form a stable 64 kDa tetramer. At this time, a total of over 500 patients have been enrolled and more than 300 patients have been treated with Hb raffimer. Preliminary analysis of data from recent Phase II & III clinical trials of Hb raffimer in routine coronary artery bypass grafting surgery suggest that the product is well tolerated and may facilitate avoidance of allogeneic blood product transfusion in this surgical setting. CONCLUSION: The converging evidence from clinical studies with HBOCs has demonstrated that these products have the potential to provide hemoglobin and oxygen carrying capacity to tissues in times of acute anemia during surgery. It is anticipated that Hb raffimer will be used to facilitate intraoperative autologous donation and emerge as an important alternative to allogeneic blood transfusion during cardiac surgery.
PURPOSES: There are currently two major classes of oxygen therapeutics: hemoglobin based oxygen carriers (HBOCs) and synthetic perfluorocarbons (PFCs). This review focuses on the use of o-raffinose cross-linked human hemoglobin (Hb raffimer) in cardiac surgery. SOURCE: The literature on HBOCs was reviewed and the development and clinical trials on Hb raffimer were outlined. PRINCIPAL FINDING: The benefits of HBOCs include avoidance of known viruses, pathogens and cross-matching; increased stability and storage time; and efficient oxygen delivery to tissues. The limitations of HBOCs include binding the endogenous vasodilator, nitric oxide, thereby resulting in transient hypertension, esophageal dysfunction and abdominal discomfort. The short half-lives of these products makes them best suited to situations of acute anemia. Hb raffimer is prepared from outdated red blood cells, cross-linked with o-raffinose, a polyaldehyde obtained through the oxidation of the trisaccharideraffinose. The Hb is covalently cross-linked (beta-beta) within the 2,3 DPG binding pocket to form a stable 64 kDa tetramer. At this time, a total of over 500 patients have been enrolled and more than 300 patients have been treated with Hb raffimer. Preliminary analysis of data from recent Phase II & III clinical trials of Hb raffimer in routine coronary artery bypass grafting surgery suggest that the product is well tolerated and may facilitate avoidance of allogeneic blood product transfusion in this surgical setting. CONCLUSION: The converging evidence from clinical studies with HBOCs has demonstrated that these products have the potential to provide hemoglobin and oxygen carrying capacity to tissues in times of acute anemia during surgery. It is anticipated that Hb raffimer will be used to facilitate intraoperative autologous donation and emerge as an important alternative to allogeneic blood transfusion during cardiac surgery.