Dialysate sodium management in hemodialysis and online hemodiafiltration: The single‐pool kinetic model revisited

Abstract

Background Determining the optimal dialysate sodium remains one of the challenges of hemodialysis prescription. Several arguments suggest that the dialysate sodium should be individually adjusted according to the patient's natremia. This strategy is greatly facilitated by using an algorithm. Only three such algorithms have been embedded in hemodialysis machines for the widespread generalization of this strategy in clinical routine: the Diacontrol (Hospal‐Baxter Healthcare Corp., Deerfield, IL, USA), the HFR‐Aequilibrium (Bellco‐Medtronic, Dublin, Ireland), and the Na‐control (Fresenius Medical Care, Bad‐Homburg, Germany). Methods Model the solute mass‐transfer across the dialyzer membrane in online hemodiafiltration and adapt the Diacontrol algorithm based on a single‐pool kinetic model of sodium balance for quantifying ionic balance and managing tonicity. Results (1) Substituting sodium measurements with conductivity measurements allows the control of tonicity which is a more physiological parameter than natremia. (2) Consideration of all ion exchanges as a whole and not just sodium exchange avoids some of the assumptions required by kinetic modeling of sodium balance. (3) Equations provided by the model are applicable to both hemodialysis and online hemodiafiltration. (4) The differences between this model used by Diacontrol and the models on which the other two software's (HFR‐Aequilibrium and Na‐control) are based are highlighted. Conclusions The single‐pool kinetic model developed for the management of natremia in hemodialysis is also valid for the management of tonicity for both conventional hemodialysis and all online hemodiafiltration procedures.

Automated adjustment of dialysate sodium by the hemodialysis monitor: Rationale, implementation, and clinical benefits

“…Some hemodialysis monitors calculate an online value of plasma‐water conductivity as a surrogate for natremia. Indeed, since sodium, together with the accompanying anion to ensure electroneutrality, is the main determinant of plasma‐water conductivity, there is a strong correlation between plasma‐water conductivity and natremia with a natremia/plasma‐water conductivity ratio close to 10 (mmol/L)/(mS/cm) 33 . Thus, the plasma‐water conductivity value (mS/cm) is usually converted into a value (mmol/L) of natremia (online natremia), which is displayed on the screen of some hemodialysis machines.…”

“…Diacontrol, based on an algorithm using a single‐pool kinetic model, 33 was the first software integrated into a hemodialysis machine for automated management of dialysate sodium. It consists of feedback between PWC and dialysate sodium (Figure 2).…”

“…Indeed, since sodium, together with the accompanying anion to ensure electroneutrality, is the main determinant of plasma-water conductivity, there is a strong correlation between plasma-water conductivity and natremia with a natremia/plasma-water conductivity ratio close to 10 (mmol/L)/ (mS/cm). 33 Thus, the plasma-water conductivity value (mS/cm) is usually converted into a value (mmol/L) of natremia (online natremia), which is displayed on the screen of some hemodialysis machines. A study by Moret et al 34 showed that the intra-individual coefficient of variation of pre-dialytic plasma-water conductivity (1.3%) is as low as that of pre-dialytic natremia (1.4%).…”

Personalized Management of Sodium and Volume Imbalance in Hemodialysis to Mitigate High Costs of Hospitalization

“…An automated and active dialysate sodium concentration adjustment to patient's plasma sodium concentration while assessing sodium mass removal has been advocated by experts [109]. The tight linear relationship between sodium content and conductivity of saline solutions enables the continuous estimation of sodium levels (compensated for potassium changes) during each HD session [96,[110][111][112]. Conductivity kinetic modeling tools that facilitate the control of diffusive sodium transfer during therapy have been advanced in recent years by using modern sensors and analytics and allow for inexpensive, accurate, and individualized sodium balance and prescriptions [28,84,90,103,[110][111][112][113].…”

“…The tight linear relationship between sodium content and conductivity of saline solutions enables the continuous estimation of sodium levels (compensated for potassium changes) during each HD session [96,[110][111][112]. Conductivity kinetic modeling tools that facilitate the control of diffusive sodium transfer during therapy have been advanced in recent years by using modern sensors and analytics and allow for inexpensive, accurate, and individualized sodium balance and prescriptions [28,84,90,103,[110][111][112][113]. In this setting, sodium mass removal and free water may be managed almost independently by the sodium module following physician prescription and patient's profile.…”