[Cryopreservation of erythrocytes using hydroxyethyl starch: in vivo results of an autologous retransfusion model in humans]

The cryopreservation of human red blood cells (RBC) can be greatly beneficial in certain situations such as for rare blood groups, problems due to multiple antibodies, and as an interim aid during temporary shortages. Additionally, cryopreserved erythrocytes may be useful in cases of civil or military disasters. Frozen/thawed autologous RBC are of particular interest as a supplement to liquid storage for elective operations (e.g. orthopedics, vascular and transplantation surgery) to extend the preoperative collection period, which is otherwise limited to 7 weeks. In this study using 7 healthy volunteers, 500 ml of whole blood was replaced by a suspension of cryopreserved autologous RBC [2 aliquots of 216 ml each, hematocrit (HCT) 43 +/- 2% (v/v), HES (hydroxyethyl starch) concentration 11.5% (w/w)]. No washing step was performed after thawing. Viability of the red cells after thawing in terms of saline stability reached 91.9 +/- 0.7% (n = 4). In all 7 cases the frozen/ thawed autologous RBC were tolerated very well. No adverse reactions could be detected. A slight posttransfusional leukocytosis as well as a moderate increase in LDH and bilirubin were observed, but these effects disappeared within 20 h. The concentrations of platelets, electrolytes, urea, protein and creatinine within their physiological ranges. The activities of the liver enzymes and the coagulation parameters investigated remained unchanged. Initially the level of free plasma hemoglobin increased by a factor of 2. Then it decreased within 20 h, accompanied by a restoration of haptoglobin. More than 85% of the HES was eliminated from the plasma within the 1st day.