Electrolyte concentration during haemodialysis and QT interval prolongation in uraemic patients

Aims To assess the effect of different combinations of potassium and calcium concentrations on QT interval in the dialysis bath in uraemic patients. Methods and results Sixteen haemodialysis (HD) patients underwent a 24 h Holter recording before and during HD sessions with six randomized combinations of electrolytes concentrations of the dialysis bath (K+, 2 and 3 mmol/L; Ca2+, 1.25, 1.5, and 1.75 mmol/L). The effect of different dialysis baths on QT interval was significant (P < 0.05). The longest mean QTc was observed with the lowest K+ (2 mmol/L) and Ca2+ concentrations (1.25 mmol/L), whereas the shortest mean QTc was observed with the highest K+ (3 mmol/L) and Ca2+ concentrations (1.75 mmol/L). QTc was > 440 ms in 9 of 16 patients (56%) at the lowest Ca2+ and K+ concentrations, and in 3 of 16 patients (18%) at the highest electrolytes level. Changes in QTc during the HD sessions were inversely correlated with that in total Ca and Ca2+ plasma concentrations (P < 0.0001). Conclusion Changes in ventricular repolarization duration associated with HD largely depend on the concentrations of Ca2+ and K+ in the dialysis bath. These findings may have important implications for the choice of the electrolytes concentration of the dialysis bath during the HD session.