Polymerized pyridoxylated hemoglobin: a red cell substitute with normal oxygen capacity.

Polymerization of pyridoxylated stroma free hemoglobin (poly SFH-P) yields a solution with a normal hemoglobin concentration, normal colloid osmotic pressure (COP), and a suitable P50. In the present study we compared its in vivo O2-carrying capacity and intravascular persistence with those of pyridoxylated hemoglobin (SFH-P), following a partial exchange transfusion (900 ml) in adult baboons (n = 4 in each group). Poly SFH-P in plasma had an O2-carrying capacity that was 77% greater than that achieved with SFH-P (8.0 versus 4.5 vol%). Furthermore, poly SFH-P provided 5.0 vol% at the end of 24 hours and 2.5 vol% at the end of 48 hours; in contrast SFH-P provided only 2.2 vol% at the end of 6 hours and none within 24 hours. A normal COP was maintained throughout the postexchange period with poly SFH-P despite a 68% increase in plasma protein concentration (from 7.1 to 11.9 gm/dl). The plasma P50 of poly SFH-P decreased from 16 torr immediately after exchange to 12 torr at the end of 48 hours. The in vivo rate of conversion to methemoglobin was similar with both solutions. Polymerized pyridoxylated hemoglobin is currently the only modification of hemoglobin solution that approximates the O2-carrying capacity of whole blood and can be infused without altering the plasma COP.