Fibrinogen salvage during DF Thermo using Evaflux-5A plasma fractionators

DF Thermo, a modified form of double-filtration plasmapheresis (DFPP), has been used for the treatment of various indications such as arteriosclerosis obliterans (ASO). In case of ASO, fibrinogen is a substance to be removed by DFPP. On the other hand, plasmapheresis for chronic viral hepatitis C became an insurance covered treatment in Japan in April 2008. Since then DFPP has also become a treatment of chronic viral hepatitis C as an adjunctive therapy for the purpose of improving the effect of medication. Therefore, there has been a growing concern in recent years about patients' low fibrinogen levels due to DFPP treatment. With the aim of improving fibrinogen retention by DF Thermo, we examined by in vitro trial, the effects when recirculating the filtrate and elevating its temperature. The trial was conducted using bovine plasma, run through experimental circuits with the same configuration as the clinical setting of the One-Way method and DF Thermo method. The DF Thermo circuit contained a thermostat, on which the temperature was set to 40°C. Two One-Way method circuits were prepared with different temperature settings, i.e., 20°C and 40°C. With these three different conditions, variance of the fibrinogen retention under different temperatures and the implementation of recirculation were compared. Results show that the DF Thermo circuit tends to have enhanced the fibrinogen retention compared to the One-Way method 20°C and 40°C. The explanation is likely as follows: viscosity of plasma reduces when warmed, which in turn helps maintain the permeability of membrane, and the recirculation of the plasma helps prevent membrane fouling, thus more fibrinogen is retained in the DF Thermo method.