Effects of Dialysate Flow Configurations in Continuous Renal Replacement Therapy on Solute Removal: Computational Modeling

Abstract

Background/Aims: Continuous renal replacement therapy (CRRT) is commonly used for critically ill patients with acute kidney injury. During treatment, a slow dialysate flow rate can be applied to enhance diffusive solute removal. However, due to the lack of the rationale of the dialysate flow configuration (countercurrent or concurrent to blood flow), in clinical practice, the connection settings of a hemodiafilter are done depending on nurse preference or at random. Methods: In this study, we investigated the effects of flow configurations in a hemodiafilter during continuous venovenous hemodialysis on solute removal and fluid transport using computational fluid dynamic modeling. We solved the momentum equation coupling solute transport to predict quantitative diffusion and convection phenomena in a simplified hemodiafilter model. Results: Computational modeling results showed superior solute removal (clearance of urea: 67.8 vs. 45.1 ml/min) and convection (filtration volume: 29.0 vs. 25.7 ml/min) performances for the countercurrent flow configuration. Countercurrent flow configuration enhances convection and diffusion compared to concurrent flow configuration by increasing filtration volume and equilibrium concentration in the proximal part of a hemodiafilter and backfiltration of pure dialysate in the distal part. In clinical practice, the countercurrent dialysate flow configuration of a hemodiafilter could increase solute removal in CRRT. Nevertheless, while this configuration may become mandatory for high-efficiency treatments, the impact of differences in solute removal observed in slow continuous therapies may be less important. Under these circumstances, if continuous therapies are prescribed, some of the advantages of the concurrent configuration in terms of simpler circuit layout and simpler machine design may overcome the advantages in terms of solute clearance. Conclusion: Different dialysate flow configurations influence solute clearance and change major solute removal mechanisms in the proximal and distal parts of a hemodiafilter. Advantages of each configuration should be balanced against the overall performance of the treatment and its simplicity in terms of treatment delivery and circuit handling procedures.

Investigating the Dialysis Treatment Using Hollow Fiber Membrane: A New Approach by CFD

“…In addition to the aforementioned research, numerical works can be found discussing dialysis treatment from the perspective of chemical species transfer, such as Gostoli and Gatta [ 15 ], who studied mass transfer in countercurrent and concurrent flow in a capillary; Ding et al [ 16 ], when developing a double porous zone model for mass transfer in a hemodialyzer, and Kanchan and Maniyeri [ 17 ], Liao et al [ 18 ], Lu and Junfeng Lu, [ 6 ] and Donato et al [ 19 ] when studying the solute transport in hemodialysis membranes with a two-dimensional approach. However, to investigate the dialysis process from the perspective of momentum transport, Choi et al [ 20 ] and Kim et al [ 21 ] modeled the blood as a multiphase fluid.…”

Etiological factors, prognostic assessment, and outcomes of patients with acute kidney injury and multiple organ dysfunction syndrome

“…The 2011 KDOQI Guide reports that the cause of the disease should be determined first followed by the classification of the risk degree and deciding the next therapeutic schedule on the basis of the established cause and risk degree (AKI guideline for AKI, 2011). The mortality rate of AKI can be decreased if the disease is diagnosed early and treated in a timely manner, and replacement therapy is administered at the right time (Sesso et al, 2004;Bagshaw et al, 2006;Basile, 2008;Bentley, 2011;Kim et al, 2013).…”

Nomenclature for renal replacement therapy in acute kidney injury: basic principles

“…A counter-current configuration is preferred because the average concentration gradient is kept higher along the whole length of the dialyzer. Conversely, a co-current configuration guarantees better stability and control of hydrodynamic conditions, and better air removal during the priming phase [ 13 ]. High-flux filters permit achievement of significant convective transport: this modality is called high-flux hemodialysis [ 14 ].…”