High versus low dialysate sodium concentration in chronic haemodialysis patients: a systematic review of 23 studies

BACKGROUND: It is the object of debate whether a low or high dialysate sodium concentration (DNa+) should be advocated in chronic haemodialysis patients. In this paper, we aimed at evaluating benefits and harms of different DNa+ prescriptions through a systematic review of the available literature. METHODS: MEDLINE and CENTRAL databases were searched for studies comparing low or high DNa+ prescriptions. Outcomes of interest were mortality, blood pressure (BP), interdialytic weight gain (IDWG), plasma sodium, hospitalizations, use of anti-hypertensive agents and intradialytic complications. RESULTS: Twenty-three studies (76 635 subjects) were reviewed. There was high heterogeneity in the number of patients analysed, overall study quality, duration of follow-up, DNa+ and even in the definition of 'high' or 'low' DNa+. The only three studies looking at mortality were observational. The risk of death was related to the plasma-DNa+ gradient, but was also shown to be confounded by indication from the dialysate sodium prescription itself. BP was not markedly affected by high or low DNa+. Patients treated with higher DNa+ had overall higher IDWG when compared with those with lower DNa+. Three studies reported a significant increase in intra-dialytic hypotensive episodes in patients receiving low DNa+. Data on hospitalizations and use of anti-hypertensive agents were sparse and inconclusive. CONCLUSIONS: There is currently no definite evidence proving the superiority of a low or high uniform DNa+ on hard or surrogate endpoints in maintenance haemodialysis patients. Future trials adequately powered to evaluate the impact of different DNa+ on mortality or other patient-centred outcomes are needed.