Low-potassium and glucose-free dialysis maintains urea but enhances potassium removal.

Background: The influence of potassium (K) removal on dialysis efficiency as measured by urea elimination is not clear. In this prospective, randomized, cross-over study we investigated the magnitude of K removal and its effect on urea (u) elimination during high-flux haemodialysis (HD).

Methods: Twelve stable, non-diabetic HD patients were investigated during three one-week standardized HD periods (1.8 m(2) high-flux polysulphone dialyser, treatment time 240 min, Qb = 300 ml/min, Qd = 500 ml/min, dialysate without glucose, bicarbonate 40 mmol/l), using dialysates containing 0 (0K), 1 (1K), and 2 (2K) mmol/l of K. Mass removal of K (M(K)) and u (M(U)) were measured during the mid-week treatment by partial dialysate collection. Urea reduction rate (URR) and Kt/V were determined.

Results: 0K, 1K and 2K treatments were perfectly comparable. Plasma K (PK) continuously declined reaching stable concentrations after 180 min. While 0K dialysate removed 117.1 mmol, 80.2 and 63.3 mmol (P < 0.001) were removed by 1K and 2K baths respectively. M(U) was not influenced by M(K) (r = 0.22) and amounted to 491.1 (0K), 508.6 (1K), and 506.2 (2K) mmol (NS) respectively. Accordingly, urea clearance, URR and Kt/V were constant during 0K, 1K and 2K treatments.

Conclusions: Potassium-free dialysate significantly enhances potassium elimination. Potassium removal has no influence on urea elimination. High potassium removal, when needed, does not impair dialysis efficiency as measured by urea kinetics in high-flux, glucose-free, 40 mmol/l bicarbonate HD.