Hemolysis in stored red blood cell concentrates: Modulation by haptoglobinor ulinastatin, a protease inhibitor

Objective: Polymorphonuclear leukocyte elastase may injure various tissues. The release of polymorphonuclear leukocyte elastase induced by various sti muli was reported to be inhibited by a protease inhibitor, ulinastatin. In stored blood preparations, polymorphonuclear leukocyte elastase increases d epending on the storage days as hemolysis increases. We hypothesized that p olymorphonuclear leukocyte elastase might be one of the factors inducing he molysis in stored blood. Haptoglobin binds to free hemoglobin to reduce hem olysis. The purpose of the study was to investigate the effects of ulinasta tin on hemolysis in blood preparations in comparison with haptoglobin. Design: In vitro study. Setting. Laboratory in a university hospital. Subjects. Nine 2-day-old packs of red blood cell concentrates (CRC) in 400 mL each of mannitol, adenine, glucose, phosphate, and citrate (MAP) (MAP-CR C) from the Japan Red Cross Society. Interventions. Each MAP-CRC was divided into three different packs of equal amount and was treated with 10 mL of saline (control group), 200 units of haptoglobin, or 50,000 units of ulinastatin. They were stored at 4 degreesC . Measurements and Main Results. Supernatant concentrations of total and free hemoglobin, total haptoglobin, polymorphonuclear leukocyte elastase, and p otassium were measured for 25 days. Free haptoglobin concentration was calc ulated. Total and free hemoglobin concentrations increased significantly de pending on the storage days in the control group, whereas haptoglobin and u linastatin groups showed no increase. Total and free haptoglobin concentrat ions were significantly higher in the haptoglobin group than in the other t wo groups. Free haptoglobin concentrations were 0 after 5 days of storage i n the control and ulinastatin groups. Polymorphonuclear leukocyte elastase concentrations increased with the increase in storage days without any diff erences among the three groups. Potassium concentration increased according to the storage and showed the highest value in the control group. Conclusions. Adding haptoglobin or ulinastatin to MAP-CRC was useful to sup press hemolysis during storage of the preparation. The polymorphonuclear le ukocyte elastase might not be involved in the mechanisms of hemolysis in MA P-CRC stored for 25 days.