Hemorrhagic Disorders After Administration of Glutaraldehyde-polymerized Hemoglobin

Glutaraldehyde is frequently used for the chemical modification of hemoglobin to improve the characteristics for use as a blood substitute. Polymerization of hemoglobin prolongs the vascular retention by increasing the molecular size. There are different ways to perform the cross-linking reaction, and this determines the stability and the oxygen affinity of the final product. In our laboratory we developed a glutaraldehyde-polymerized hemoglobin solution (PolyHbXI) with a high degree of intramolecular cross-linking and lowered oxygen affinity. In preclinical safety studies, PolyHbXI was generally well tolerated. However, in three animal models (rats, rabbits and rhesus monkeys), we observed transient hemorrhagic disorders. We further analyzed this side effect in a histopathological study with rats. Hemorrhagic lesions were observed in several tissues (with predilection for the intestinal wall) two days after administration of PolyHbXI, and the lesions were resolved after one week. Microscopically, the bleedings were characterized as “small vessel vasculitis” with a neutrophil infiltration. Platelet numbers, bleeding time and APTT values were normal. This leads to the hypothesis that endothelial cell injury plays a central role in the pathophysiology. By comparing different modified hemoglobin preparations we found evidence that the toxic factor is the result of the cross-linking procedure with glutaraldehyde.