Generation of free oxygen radicals and the toxicity of hemoglobin solutions

The observed toxicity of hemoglobin solutions (HbS) might depend, at least in part, on the tendency of Hb to autoxidation with generation of oxygen free-radicals. Aims of this study were: (1) to quantitate plasma elevations of H2O2 and lipid peroxides after replacement of 1/3 of calculated blood volume in various groups of rabbits with different Hb solutions; (2) to correlate these elevations with parameters of brain, heart, lung, liver and kidney injury or dysfunction; and (3) investigate the protective effect of mannitol as a radical scavenger. One Hb solution contaminated with stromal phospholipids raised H2O2 from 31.2 +/- 1.9 to 166 +/- 20 mumol/ml, lipid peroxides from 1.62 +/- 0.5 to 7.29 +/- 0.3 nmol/ml, CK-BB (brain isoenzyme) from 250 +/- 25 to 470 +/- 50 IU/L, CK-MB (myocardial isoenzyme) from 2.98 +/- 0.03 to 10.73 +/- 1.3 IU/L and SGPT from 38.1 +/- 5 to 167 +/- 45 IU/L, and reduced PaO2 from 87 +/- 10 to 57.5 +/- 2.5 mm Hg and creatinine clearance from 1.5 +/- 0.3 to 0.13 +/- 0.03 mg/min/Kg. These changes were progressively less severe with pure unmodified Hb, pure Hb crosslinked with "o-ATP", and pure crosslinked Hb + mannitol (4 mg/ml). These observations indicate a significant role for oxygen-derived radicals in the toxicity of Hb solutions.