Flow balance optimization and fluid removal accuracy with the Quanta SC+ hemodialysis system.

BACKGROUND: Fluid management is integral to hemodialysis, both to correct abnormalities in a patient's plasma composition and to maintain fluid balance. Consequently, accurate net fluid removal during treatment is a critical design element of hemodialysis machines. As dialyzers have evolved, with increased ranges of ultrafiltration coefficients available, it has become more challenging for dialysis machines to minimize errors in flow balance and net fluid removal. RESEARCH DESIGN AND METHODS: This paper describes the design, evaluation and experimental performance of the flow balance and ultrafiltration module of the SC+ system to deliver clinically specified fluid removal with both passive and active control measures, in laboratory conditions designed to simulate a wide range of therapies. RESULTS: The use of passive and active control allows the errors to be minimized across a wider dynamic range of conditions. For the SC+ system, the average flow balance error was 1 mL/hr with an SD of 19 mL/hr and with ultrafiltration it was 13 mL/hr and an SD of 20 ml/hr across all conditions. CONCLUSIONS: This paper demonstrates that the SC+ hemodialysis system, a small, simple and versatile CE marked device, operates within the limits required by international standards across a wide range of experimental conditions.

Enhancement of solute clearance using pulsatile push-pull dialysate flow for the Quanta SC+: A novel clinic-to-home haemodialysis system.

BACKGROUND AND OBJECTIVE: The SC+ haemodialysis system developed by Quanta Dialysis Technologies is a small, easy-to-use dialysis system designed to improve patient access to self-care and home haemodialysis. A prototype variant of the standard SC+ device with a modified fluidic management system generating a pulsatile push-pull dialysate flow through the dialyser during use has been developed for evaluation. It was hypothesized that, as a consequence of the pulsatile push-pull flow through the dialyser, the boundary layers at the membrane surface would be disrupted, thereby enhancing solute transport across the membrane, modifying protein fouling and maintaining the surface area available for mass and fluid transport throughout the whole treatment, leading to solute transport (clearance) enhancement compared to normal haemodialysis (HD) operation. METHODS: The pumping action of the SC+ system was modified by altering the sequence and timings of the valves and pumps associated with the flow balancing chambers that push and pull dialysis fluid to and from the dialyser. Using this unique prototype device, solute clearance performance was assessed across a range of molecular weights in two related series of laboratory bench studies. The first measured dialysis fluid moving across the dialyser membrane using ultrasonic flowmeters to establish the validity of the approach; solute clearance was subsequently measured using fluorescently tagged dextran molecules as surrogates for uraemic toxins. The second study used human blood doped with uraemic toxins collected from the spent dialysate of dialysis patients to quantify solute transport. In both, the performance of the SC+ prototype was assessed alongside reference devices operating in HD and pre-dilution haemodiafiltration (HDF) modes. RESULTS: Initial testing with fluorescein-tagged dextran molecules (0.3 kDa, 4 kDa, 10 kDa and 20 kDa) established the validity of the experimental pulsatile push-pull operation in the SC+ system to enhance clearance and demonstrated a 10 to 15% improvement above the current HD mode used in clinic today. The magnitude of the observed enhancement compared favourably with that achieved using pre-dilution HDF with a substitution fluid flow rate of 60 mL/min (equivalent to a substitution volume of 14.4 L in a 4-hour session) with the same dialyser and marker molecules. Additional testing using human blood indicated a comparable performance to pre-dilution HDF; however, in contrast with HDF, which demonstrated a gradual decrease in solute removal, the clearance values using the pulsatile push-pull method on the SC+ system were maintained over the entire duration of treatment. Overall albumin losses were not different. CONCLUSIONS: Results obtained using an experimental pulsatile push-pull dialysis flow configuration with an aqueous blood analogue and human blood ex vivo demonstrate an enhancement of solute transport across the dialyser membrane. The level of enhancement makes this approach comparable with that achieved using pre-dilution HDF with a substitution fluid flow rate of 60 mL/min (equivalent to a substitution volume of 14.4 L in a 4-hour session). The observed enhancement of solute transport is attributed to the disruption of the boundary layers at the fluid-membrane interface which, when used with blood, minimizes protein fouling and maintains the surface area.