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

Background. The influence of potassium (K) removal on dialysis efficiency a s measured by urea elimination is not clear. In this prospective, randomize d, crossover study we investigated the magnitude of K removal and its effec t on urea (u) elimination during high-flux haemodialysis (HD). Methods. Twelve stable, non-diabetic HD patients were investigated during t hree one-week standardized HD periods (1.8 m(2) high-flux polysulphone dial yser, treatment time 240 min, Qb = 300 ml/min, Qd = 500 ml/min, dialysate w ithout 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 m easured 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 O K 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) respectivel y. Accordingly, urea clearance, URR and Kt/V were constant during OK, 1K an d 2K treatments. Conclusions. Potassium-free dialysate significantly enhances potassium elim ination. Potassium removal has no influence on urea elimination. High potas sium removal, when needed, does not impair dialysis efficiency as measured by urea kinetics in high-flux, glucose-free, 40 mmol/l bicarbonate HD.