What Is the Optimal Dialysate Sodium Concentration?

In haemodialysis, sodium and fluid balance (where intake matches loss) is achieved by ultrafiltration and by diffusion between the plasma water and dialysate. If a patient’s sodium intake does not change, any reduction in fluid gain obtained by lowering dialysate sodium concentration will result in less sodium removal by ultrafiltration. The corresponding change in diffusion to achieve balance may mean the benefit of lower fluid gain is offset by morbidity caused by a fall in serum sodium during dialysis. The standard dialysate sodium should minimise harm caused by both high ultrafiltration rates and osmotic disequilibrium. For most units, this is likely to be 138 to 140 mmol/L.