Dialysate Potassium, Dialysate Magnesium, and Hemodialysis Risk

Abstract

One of the fundamental goals of the hemodialysis prescription is to maintain serum potassium levels within a narrow normal range during both the intradialytic and interdialytic intervals. Considering the extraordinarily high rate of cardiovascular mortality in the hemodialysis population, clinicians are obligated to explore whether factors related to dialytic potassium removal can be modified to improve clinical outcomes. Observational studies and circumstantial evidence suggest that extreme concentrations of serum and dialysate potassium can trigger cardiac arrest. In this review, we provide an overview of factors affecting overall potassium balance and factors modulating potassium dialysate fluxes in dialysis, and we review data linking serum and dialysate potassium concentrations with arrhythmias, cardiovascular events, and mortality. We explore potential interactions between serum and dialysate magnesium levels and risks associated with dialysate potassium levels. Finally, we conclude with proposed dialytic and novel nondialytic approaches to optimize outcomes related to potassium homeostasis in patients on hemodialysis. Dialysis clinicians need to consider changes in the overall clinical scenario when choosing dialysate potassium concentrations, and an effective change in practice will require more frequent serum potassium monitoring and responsive dialysis care teams.

Keywords: chronic hemodialysis; clinical epidemiology; electrolytes; end stage renal disease.

Figure 1.

Comparison of intradialytic and postdialytic potassium levels between a serum-dialysate gradient of 5.8 mEq/L (solid line; predialysis serum potassium 6.8 mEq/L and dialysate potassium 1 mEq/L) and a gradient of 4.7 mEq/L (dashed line; predialysis serum potassium 5.7 mEq/L and dialysate potassium 1 mEq/L). The high serum-dialysate gradient condition results in a total excursion of serum potassium levels of approximately 5 mEq/L (3 mEq/L fall and 2 mEq/L rebound) in the 10 hours after the start of treatment compared with approximately 3 mEq/L with the lower gradient condition. Modified from Blumberg et al., with permission.

Figure 2.

Sudden cardiac arrest (SCA) risk according to serum and dialysate potassium. The risk of SCA remains higher or equivalent (overlapping 95% confidence intervals) with lower-potassium dialysate <2 mEq/L compared with ≥2, even among patients who are hyperkalemic. Reprinted from Pun et al., with permission.

Figure 3.

Adjusted associations between the serum magnesium level and all-cause mortality among 142,555 patients on HD. The dashed lines represent the 95% confidence intervals. Reprinted from Sakaguchi et al., with permission.

Figure 4.

Mean serum and dialysate potassium levels in the months preceding peridialytic sudden cardiac arrest (n=97 patients with peridialytic sudden cardiac arrest exposed to low-potassium dialysate <2 mEq at the time of arrest). Despite falling average serum potassium levels, prescription of low dialysate potassium increased in the months preceding cardiac arrest. P.H. Pun et al., unpublished data.