Low dialysate sodium concentrations have been associated with intradialytic symptoms such as muscle cramps and hypotensive episodes. High dialysate sodium concentrations lead to sodium loading, thirst and subsequent increase in interdialytic weight gain and hypertension. The optimal dialysate sodium concentration for an individual depends on the serum sodium concentration. The difference between the dialysate sodium concentration and the predialysis serum sodium concentration has been defined as the sodium gradient. In this article, the role of the sodium gradient in fluid overload, hypertension, intradialytic symptoms and clinical outcome is discussed. Absolute serum sodium levels should always be taken into account when interpreting the relation between sodium gradient and clinical outcomes. Alignment of the dialysate sodium with the serum sodium concentration may be beneficial in many patients.
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