A comparison of dual dialyzers in parallel and series to improve urea clearance in large hemodialysis patients.

Background: Dialysis adequacy targets frequently are difficult to achieve in large hemodialysis patients. Dual dialyzers can be used to improve clearance. It is unknown whether series or parallel configurations are superior.

Methods: Eighteen large hemodialysis patients (mean weight, 92.4 kg) were enrolled in a randomized, crossover trial to directly compare dual dialyzers in parallel and series configurations. Treatment times, blood flow rates, and dialysate flow rates were kept constant.

Results: Compared with a single dialyzer, parallel dual dialyzers increased the single-pool Kt/V (spKt/V) from 1.25 +/- 0.22 to 1.43 +/- 0.29 (P < 0.003). Series dual dialyzers improved urea clearance measured by spKt/V (spKt/V(urea)) to 1.46 +/- 0.26 (P < 0.0003 compared with a single dialyzer). Kt/V and urea reduction ratio of dual dialyzers in parallel were not significantly different from those of dual dialyzers in series. Half the subjects failed to meet the National Kidney Foundation-Kidney Disease Outcomes Quality Initiative recommended adequacy target for spKt/V(urea) of 1.2 or less using a single dialyzer. With the use of dual dialyzers, 83% of subjects achieved this adequacy target. Serum levels of a middle molecule, beta2-microglobulin, were reduced 34% after 2 months of dual-dialyzer therapy. Cost analysis estimates annual net savings of 1,260 dollars with dual-dialyzer therapy, primarily from projected savings in inpatient expenses.

Conclusion: In large hemodialysis patients, our study shows that dual dialyzers in parallel and series are equally effective at improving urea clearance without prolonging dialysis treatment times.