**4. Conclusion**

132 Progress in Hemodialysis – From Emergent Biotechnology to Clinical Practice

Fig. 9. Schematic Diagram of PPPHD with Dual Piston Pump. (D, dialysate pump; E,

Fig. 10. Pulse Generation and Push/Pull during PPPHD with Dual Piston Pump. (D,

dialysate pump; E, effluent pump)

effluent pump)

Much evidence shows that HDF delivers better dialysis outcomes than high-flux HD; for example, HDF has been shown to improve middle-to-large size molecular removal, allow better EPO control, reduce oxidative stress and inflammation (Lornoy et al., 2000, Vaslaki et al., 2006, Ward et al., 2000), and even to positively influence patient mortality (Canaud et al., 2006, Jirka et al., 2006). These benefits have been attributed to the higher convective doses permitted during HDF. Furthermore, ultrapure dialysate, required due to the large amount of substitution infusion, further inhibits the inflammation risk (Lonnemann, 2000).

In this chapter, we review HDF techniques that do not require exogenous substitution infusion. These techniques must be accompanied by spontaneous fluid restoration, such as, backfiltration or ultrafiltrate regeneration (Table 3). A simpler way might be to increase forward and backward filtration rates during HD sessions, although this can only be done to a limited extent. Much higher efficiencies can be achieved by the two-chamber techniques, that is, double high-flux HDF and HFR, which were developed in an effort to increase solute removal and shorten treatment times, by separating ultrafiltration and backfiltration, or convection and diffusion domains. However, these modalities appear to unavoidably increase overall system complexity. Push/pull HDF, which uses a single hemodialyzer, was derived by considering phases, rather than physical regions, for forward and backward filtration. The pulse push/pull HD described here is also based on the phase-separated use of forward filtration and backfiltration using a single high-flux dialyzer. This strategy was devised as a result of efforts to modulate flow patterns for extracorporeal dialysis treatment, and thus, a unique design for managing dual pulsation through the dialysate compartment allows the whole unit to be as simple as the conventional HD unit.

Pulse Push/Pull Hemodialysis: Convective Renal Replacement Therapy 135

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As these novel HDF strategies evolved, remarkable improvements have been achieved in dialysis technologies. Modern dialysis machines offer HDF and HD as default therapies, and are also equipped with outstanding monitoring facilities not only for patients (BTM, BVM, OCM2), but also for treatments (fail-safe design and high-precision balancing) (Polaschegg, 2010). In particular, advances in water treatment allow ultrapure replacement fluid to be prepared in real time. These technical advancements are certainly lowering the barriers to higher convective HDF therapies.


§ Total filtration volume per session (4 hours, L); +, low (<20L); ++, moderate (20-40L); +++ high (>60L)

Table 3. Infusion-free HDF modalities. (HFR, hemofiltrate reinfusion; TFV, total filtration volume; PP, push/pull; FR, filtrate regeneration; BF, backfiltration)

Therefore, in addition to convective clearances, we believe the PPPHD system should be equipped by features that simplify overall treatment and enable dialysis to be performed in outside clinics, because this unit allows simple and efficient operation. Future development targets designed to accomplish these features include; greater user friendliness (that is, intuitive control and operation, fail-safe operations and treatment automation), readily available sterile dialysate, accessible maintenance, and a miniaturized unit that is both light and portable (without compromising depurative efficiency). A dialysis unit equipped with these features may also provide treatment alternatives beyond the current thrice weekly 4-h practice, and perhaps allow even daily dialysis for ESRD patients.
