Evaluation of methemoglobin formation during the storage of various hemoglobin solutions.

Many researchers are trying to develop a blood substitute based on chemically modified human hemoglobin. In the process of making such solutions, we were faced with the problem of determining the best storage conditions to minimize oxidation of the solutions between the time of manufacture and use. Samples of stroma-free hemoglobin, purified A0 hemoglobin, and various cross-linked hemoglobins were stored for 8-12 months at +4 degrees C -20 degrees C, and -80 degrees C and were analyzed periodically for formation of methemoglobin (MetHb). Various suspending solutions were evaluated for their effects on the rate of MetHb formation, and the approximate rates of MetHb production per month were calculated. Short-term storage of hemoglobin solutions (< 14 days) can be done at +4 degrees C, but extended storage should be done at -80 degrees C with quick thawing. Salts minimize the hemoglobin oxidation during the stress of freeze-thaw operations. Storage at -20 degrees C. presents further problems and should be avoided.