What Are Hemoglobin-Based Oxygen Carriers?

Within each red blood cell are some 300 million hemoglobin molecules. Hemoglobin represents about one third of the volume of a mature red cell. Each molecule contains the protein globin and a pigment called heme - which includes an iron atom. When a red blood cell passes through the lungs, oxygen molecules penetrate the cell and attach themselves to hemoglobin molecules. Seconds later, the oxygen is discharged into body tissue, sustaining the life of the cells.

Some manufacturers now process hemoglobin, releasing it from human or bovine red blood cells. The extracted hemoglobin is then filtered to remove impurities, chemically modified and purified, mixed with a solution, and packaged. The end product—not yet approved for use in most lands—is called a hemoglobin-based oxygen carrier, or HBOC. Since the heme is responsible for the rich red color of blood, a unit of HBOC looks just like a unit of red blood cells, the primary component from which it is taken.

Unlike red blood cells, which must be refrigerated and discarded after a few weeks, the HBOC can be stored at room temperature and used months later. And since the cell membrane with its unique antigens is gone, severe reactions due to mismatched blood types pose no threat.