Effects of hypothermic conditions on the oxygen carrying capacity of crosslinked hemoglobins.

In view of the potential application for hemoglobin-based oxygen carriers (HBOCs) in organ perfusion under hypothermic conditions, we examined the temperature dependence of oxygen equilibrium curves (OECs) at 15-37 degrees C of three HBOCs: HbA-FMDA and HbBv-FMDA, produced by the reaction of human or bovine oxyHb with fumaryl mono-dibromoaspirin, and HbA-DBBF, produced by the reaction of human deoxyHb with bis(3,5-dibromosalicyl) fumarate. OECs for HbA-DBBF, HbA-FMDA and HbBv-FMDA at 37 degrees C were right shifted (P50 = 24.5, 17 and 35 torr, respectively). van't Hoff's rule gave HbA-DBBF (-12.2 +/- 2.8), HbA-FMDA (-12.0 +/- 2.0), HbBv-FMDA (-10.5 +/- 1.8); these values do not significantly differ from that for native HbAo (-11.5 +/- 2.4). Among the hemoglobins included in this study, HbBv-FMDA had the most favorable oxygenation characteristics at low temperatures (a P50 of 6.0 torr at 15 degrees C as compared to only 2-3 torr for the other hemoglobins in the study). Recently, however, a human hemoglobin crosslinked with bis-pyridoxyl tetraphosphate was reported to have a P50 of 15 torr at 16 degrees C (Keipert et al, Transfusion 1989; 29: 768-773). Therefore, precise knowledge of the oxygen delivering capacity of any potential HBOC should be explored under hypothermic conditions as performance under these conditions may determine its usefulness as an organ perfusate.