Common dietary sources of K+ include certain fruits and vegetables, as well as cereals and unprocessed meat and fish. Nevertheless, the bioavailability of K+ differs between various sources, and is highest from salt substitutes and K+-containing additives (24, 25). The net base-producing plant-based foods high in K+ may boost cellular K+ uptake due to alkaline milieu and by stimulating the release of endogenous insulin (26). This enhances K+ uptake by the cells, thus attenuating the rise of serum K+. Furthermore, it may promote K+ removal by the stool, by increasing faecal bulk (27). The myth that consumption of K+-rich plant-based diet should be avoided has been refuted by recent studies that have demonstrated an association between such a diet and lower mortality in CKD patients, as long as urinary K+ excretion is preserved (28-33). Moreover, the well-known renoprotective effect of K+ in the general population is currently being investigated in a randomised, double-blind, placebo-controlled study including patients with CKD stages 3b to 4 (33-37). The hope is that novel K+ binders will enable the consumption of plant-based heart-healthy diets in CKD patients.
Interdialytic hyperkalaemia: A step towards optimal care
HK is prevalent in 30–50% of long-term haemodialysis patients, and higher serum potassium levels are associated with an increased risk of mortality in these patients (38-40). In the first hour of dialysis, there is a rapid fall in K+ levels; however, HK returns within 6 hours after haemodialysis (41-45). It has been demonstrated that almost three quarters of all arrhythmias occurred during or immediately after dialysis, and this is assumed to be related to the changes in K+ levels which occur during the dialysis sessions (46). In patients on haemodialysis, dietary K+ restriction is associated with a high rate of non-adherence, malnutrition, and increased morbidity and mortality (27, 47-49). Traditional potassium binders such as sodium polystyrene sulphonate (SPS) can be used for the management of HK; however, the long-term efficacy of these treatments has yet to be robustly demonstrated in patients on dialysis (47, 50-52). SPS is also poorly tolerated due to its unpleasant taste and texture (50). Data on how to optimally manage HK in patients on dialysis are limited. However, newer K+ binders may improve the management of a broad spectrum of patients at all stages of CKD (53-55). DIALIZE is the first randomised, placebo-controlled trial to evaluate the efficacy and safety of a novel K+ binder, sodium zirconium cyclosilicate (SZC), for the treatment of HK in patients on haemodialysis. The study results have demonstrated that SZC reduced serum K+ levels and sustained K+ control in haemodialysis patients. There were no differences between SZC and placebo in interdialytic weight gain, which is a marker of sodium and fluid retention. SZC was also well tolerated, with most adverse events being mild or moderate in intensity, and the adverse event profiles between the treatment groups were similar, including gastrointestinal events and hypokalaemia (56-61).