Hypokalemia and hyperkalemia may lead to potentially life threatening cardiac arrhytmias. The usual dialysate potassium level is 2 mmol/l. Low dialysate concentration, particularly those of 0 or 1 mmol/l, Should be avoided. If used, extreme caution should be exercised because the rapid decline in plasma potassium concentration, which occurs in the early stages of a dialysis treatment, is arrhythmogenic. Haemodialysis is associated with the markers of cardiac electrophysiologic abberancy, particularly in patients with underlying cardiovascular disease, and those markers are amplified by a low potassium bath. Reducing the blood-to-bath potassium gradient during dialysis mitigates the dialysis-associated electrophysiologic effects. However, the cardiacelectrophysiologic markers appear to add little or nothing to the sudden death risk assessment and so are of dubious predictive value. The risk of intradialytic hypotension inversely correlates to the potassium concentration in the dialysate. The use of 1 mmol/l potassium dialysate in a chronic hemodialysis setting has been associated with an increased incidence of cardiac arrest. Similar to sodium, potassium profiling has been suggested, but the evidence is weak.