Plasma exchange with a rotating filter.

Abstract

We have modified a rotating filter system to provide therapeutic plasma exchange. Seventeen patients underwent 188 treatments. Blood flows to the filter ranged from 75 to 100 ml/min; mean filtration fraction was 64 +/- 1% (+/- SE, N = 188). Mean plasma removal rate per treatment was 40.2 +/- 0.6 ml/min; net plasma removed per treatment was 3231 +/- 53 ml (N = 188); mean treatment time was 83 +/- 2 minutes (N = 188). Mean percent decline in platelet count was 15 +/- 4% (N = 46). Immunoglobulin kinetics were evaluated in order to validate our method of treatment prescription. The apparent volume of distribution (AVD) for each immunoglobulin class was compared to our estimate for plasma volume (EPV). The fraction AVD/EPV for IgG was 0.97 +/- 0.04 (N = 14), for IgA was 0.87 +/- 0.04 (N = 13) and for IgM was 0.96 +/- 0.3 (N = 26). Use of the EPV allowed for accurate prediction of treatment results. Correlation between expected and actual decline in serum levels revealed an r value of 0.86 for IgG (P = 0.0002), 0.88 for IgA (P = 0.0001), and 0.57 for IgM (P less than 0.003). We conclude that a rotating filter system can provide a highly efficient means of plasma exchange. The use of a simplified method of estimating plasma volume allows for a reliable prediction of treatment results.