In the case of the biodegradable cryoprotectant hydroxyethyl starch (HES) no deglycerolization process is required prior to the transfusion of frozen red blood cells (RBC). In a first study the elimination of an HES 200,000/0.62 from the plasma of 6 dogs was investigated by means of a novel HPLC-GFC method. 16% of the blood volume were replaced by autologous HES protected frozen/thawed RBC. In a second study the HES concentration in the plasma of 7 healthy volunteers was determined following the substitution of 8% of the blood volume, but a washing step has been performed to reduce the concentration of the cryoprotectant (HES 200,000/0.5). In a third study, however, this step was omitted. The elimination of the HES followed always first order kinetics. In the case of the transfusions without postthaw washing in dogs and humans, the initial plasma concentrations amounted to 2.11 +/- 0.15 g/dl and 0.75 +/- 0.26 g/dl, respectively. The corresponding value for the washed preparations was less than 0.03 g/dl. Within 4-5 h the concentrations dropped to less than 50% of the initial values. The 9-hour value was less than 35% (dogs), the 20-hour value about 15% (humans) of the initial concentration. As HES is primarily eliminated via the kidneys, within this period the concentrations of HES in the urine dropped from 4.3 +/- 2.11 g/dl to less than 0.03 g/dl (humans, no washing step). In conclusion, the elimination of the accompanying cryoprotectant HES was no problem in the concentrations applied. A simple washing step with isotonic saline, however, effectively reduced the concentration of the extracellular cryoprotectant HES far below critical levels.
