Cryopreservation of human red cells in liquid nitrogen with hydroxyethyl starch

Summary

Erythrocytes were frozen in plastic bags in liquid nitrogen with 14% (w/v) hydroxyethylstarch (HES). Both a small volume (25.0 ml) and a full unit system (405 ml) were employed. Small volume freezings were investigated to optimize container configuration, conditions, composition of media, and postthawed stability of cells. Based on this experience a method for full unit freezing of packed erythrocytes was devised.

The results of the 10 most recent experiments with 25.0 ml freezing gave postthawed cell recoveries of 99.2 ± 0.3%. Stability for 1 hr in 0.15 M NaCl at 22.0°C was 85.9 ± 4.3%. The cells gained 17 mequiv of Na⁺ and lost 21 mequiv of K⁺. The ATP decreased 23% while 2,3 DPG was unchanged.

In the large volume method using all the packed red cells in a unit after removal of platelet rich plasma and buffy coat, a single bag was sandwiched between large perforated aluminum plates. The results of eight recent freezings and short-term storage in liquid nitrogen vapor gave cell recoveries of 97.2 ± 1.1%, and stabilities in saline of 75.7 ± 1.8%. Relatively small losses of ATP and 2,3 PDG were observed. The cells gained 33 mequiv of Na⁺ and lost 31 mequiv of K⁺. Assuming acceptable 24-hr posttransfusion survival can be achieved, the feasibility of freezing full units of red cells in a one-step procedure is now demonstrated.