PolyHeme Chemistry
Northfield Labs makes PolyHeme from outdated human blood. First, hemoglobin is extracted from red blood cells. Then it is filtered to remove impurities. The next step is to modify and purify the hemoglobin to polymerize it. Polymerization causes molecules of hemoglobin to chemically link together, in an attempt to reduce the material's well-known effects when it circulates freely in the blood. 
These effects include vasoconstriction, kidney dysfunction, liver dysfunction and gastrointestinal distress. Finally, the modified hemoglobin is mixed into an electrolyte solution and packaged. Polyheme has a shelf life in excess of 12 months and does not need to be typed and matched before infusion.