A simple method for incorporating single pass dialysate delivery and controlled ultrafiltration with the RP-6 high flux dialyzer

Pressure control of ultrafiltration rate with high-flux dialysis membranes

Control of ultrafiltration with high-flux dialysis membranes is normally achieved using complex, expensive, volumetric control methods. By using high-flux dialyzers with distensible membranes (parallel-plate dialyzers) in the cocurrent rather than in the countercurrent mode, ultrafiltration can be controlled simply and inexpensively by controlling the outlet pressure differential. Since this is the traditional method of ultrafiltration control, only minor, inexpensive equipment modifications are needed. As expected from transport theory, small molecule clearances are lower with cocurrent than with countercurrent flow. They are, however, adequate and superior to those achieved with post-dilutional hemofiltration (urea clearance greater than 110 ml/min with cocurrent single-pass, high-flux dialysis). Ultrafiltration control with this method is so simple and predictable that clearances at zero net ultrafiltration rates can easily be measured rather than extrapolated. Since dialysate pressure is always positive, no deaeration systems would be needed in dialysis equipment designed for use with cocurrent single-pass, high-flux dialysis.

Controlled ultrafiltration during single-pass dialysis with the RP-6 dialyzer and evaluation of its time-dependent ultrafiltration index

A simple and inexpensive method is described for controlling ultrafiltration when using the high flux RP-6 dialyzer. When th RP-6 is operated in the co-current mode and with single-pass dialysate delivery, (PBo-PDo) can be used to accurately and safely control ultrafiltration. Combined results from ten dialyses indicate there is a pressure-dependent concentration polarization which affects ultra-filtration as reported previously, and in addition, a time-dependent effect indicating a more complex dialyzer/blood interaction. The ultrafiltration index decreases linearly with time. The ultrafiltration can be adequately predicted by (Formula: see text).