REDUCTION OF THE METHYLENE-BLUE (MB) CONC ENTRATION IN MB-PHOTOOXIDATED PLASMA BY FILTRATION

Background: Virus inactivation of fresh frozen plasma (FFP) can be ach ieved by photodynamic methods in the presence of phenothiazine dyes li ke methylene blue (MB). The potential hazard of FFP treated by this pr ocedure is still unclear, yet. Elimination of MB may reduce adverse re actions. Materials and Methods: We examined the effect of leukocyte de pletion by filtration on the remaining concentration of MB in FFP (n = 25), which was previously MB treated. 5 pools of 1,000 mi FFP each we re divided into 3 aliquots: 200 mi of every pool was deep frozen (-40 degrees C) without further preparation immediately (group I). The rema ining 800 mi was mixed with MB (1 mu mol/l) and photooxidated. 200 mi of this MB plasma was frozen without filtration (group II), the remain ing 600 mi of MB plasma was leukocyte depleted by filtration (LPS-2(R) , Pall Biomedizin, Dreieich, Germany) before freezing (group III). MB concentrations in the different groups were examined by photometry at 660 nm. Results: Compared to untreated plasma, treatment with MB in pl asma of the same pool resulted in significantly decreased factor VIII values [median and ranges: 0.50 (0.45-0.73) U/ml versus 0.65 (0.55-0.8 0) U/ml]. Filtration of the first 200 mi of the MB-treated plasma redu ced the concentration of MB by 75 +/- 21%. In larger plasma volumes, t he capacity of the filter in reducing the amount of MB decreased. Whil e coagulation factors V and VIII, von Willebrand factor and thrombin-a ntithrombin-III complex were not influenced by the filtration profess, the number of contaminating leukocytes and concentrations of beta-thr omboglobulin and platelet factor 4 decreased significantly. Conclusion : We conclude that concentrations of MB in MB-treated FFP can be lower ed by leukocyte filtration. Thereby, possible side effects of MB may b e further reduced.