Zero Diffusive Sodium Balance in Hemodialysis Provided by an Algorithm‐Based Electrolyte Balancing Controller: A Proof of Principle Clinical Study

Abstract

Artificial Organs 2019, 43(2): [150][151][152][153][154][155][156][157][158] Restoring and controlling fluid volume homeostasis is still a challenge and clearly an unmet medical need in contemporary end-stage kidney disease (ESKD) patients treated by intermittent hemodialysis as renal replacement therapy (RRT) (1). Fluid volume balance is currently achieved by combining fluid and sodium depletion by RRT: By a so-called "dry weight probing" approach referring to intra-dialytic weight loss (IDWL) (1,2), by adjusting the dialysate-to-plasma sodium gradient (3-5) and by enforcing daily dietary salt and fluid restrictions (6). The improper control of fluid volume and sodium mass balance in RRT patients leads to chronic fluid Abstract: Restoring and controlling fluid volume homeostasis is still a challenge in contemporary end-stage kidney disease patients treated by intermittent hemodialysis (HD) or hemodiafiltration (HDF). This primary target is achieved by ultrafiltration (dry weight probing) and control of intradialytic sodium transfer (dialysate-plasma Na gradient). The latter task is mostly ignored in clinical practice by applying a dialysate sodium prescription uniform for all patients of the dialysis center but unaligned to individual plasma sodium levels. Depending on the patient's natremia, a positive gradient gives rise to intradialytic diffusive sodium load and postdialytic thirst. On the contrary, a negative gradient may cause unwanted diffusive sodium removal and intradialytic symptoms. To overcome these challenges, a new conductivity-based electrolyte balancing algorithm embedded in a hemodialysis machine with the aim to achieve "zero diffusive sodium balance" in HD and online HDF treatments was tested in the form of a prospective clinical trial. The study comprised two phases: a first phase with a conventional fixed-sodium dialysate (standard care phase), followed by a phase with the electrolyte balancing control (EBC) module activated (controlled care phase). The results show a reduction in the variability of the intradialytic plasma sodium concentration shift, but it is overlain by a small but statistically significant increase in the mean plasma sodium levels. However, no clinical manifestations were observed. This sodium load can be explained by the design of the algorithm based on dialysate conductivity instead of sodium concentration. Furthermore, the increase in plasma sodium can be corrected by taking into account the potassium shift during the treatment. This study showed that the EBC module incorporated in the HD machine is able to automatically individualize the dialysate sodium to the patient's plasma sodium without measuring or calculating predialytic plasma levels from previous laboratory tests. This tool has the potential to facilitate fluid management, to control diffusive sodium flux, and to improve intradialytic tolerance in daily clinical practice.

Automated individualization of dialysate sodium concentration reduces intradialytic plasma sodium changes in hemodialysis

“…This randomized controlled crossover trial was a proof‐of‐principle study of sodium control, which offers an individual adjustment of the dialysate during treatment in order to reduce the intradialytic change of plasma sodium concentration. The underlying sodium control module and algorithm refined the dialysate side‐balancing approach based on conductivity measurements by incorporating a kinetic model correcting for the contribution of non‐sodium electrolytes in spent dialysate. As already suggested by Kuhlmann et al, this resulted in a substantial and significant reduction in the scatter of intradialytic plasma sodium changes.…”

“…In this way, the electrolyte balancing algorithm becomes a “sodium‐like balancing” algorithm that continuously matches the inlet dialysate sodium concentration to that of the outlet, virtually abolishing the inlet‐to‐outlet sodium gradient and consequently doing the same to the effective dialysate to plasma gradient.…”

“…This new “automated sodium control algorithm” was implemented in the dialysis system 5008 (Fresenius Medical Care, Bad Homburg, Germany) as the option “Na control.” To make the kinetic model applicable for clinical routine where pre‐dialytic ion concentrations are not available, this implementation instead uses parameter values derived from a clinical study . All electrolytes other than sodium are summarized in a “pseudo‐potassium” parameter because a previous study showed that a predominant part of the deviation in plasma Na kinetics from isonatremia could be explained by potassium kinetics.…”

“…Recently, a different approach has been implemented into a dialysis monitor . An automated controller continuously adjusts the dialysate inlet conductivity to that of the spent dialysate in order to keep the plasma conductivity constant.…”

“…An automated controller continuously adjusts the dialysate inlet conductivity to that of the spent dialysate in order to keep the plasma conductivity constant. A clinical study has shown that this tool reduces variability in intradialytic plasma sodium changes but at the expense of a slight but significant increase in plasma sodium . Taking into account potassium as the second most abundant cation, a zero diffusive sodium balance could be approached.…”