Relationship between measured and prescribed dialysate sodium in haemodialysis: a systematic review and meta-analysis.

BACKGROUND: Dialysate sodium (DNa) prescription policy differs between haemodialysis (HD) units, and the optimal DNa remains uncertain. We sought to summarize the evidence on the agreement between prescribed and delivered DNa, and whether the relationship varied according to prescribed DNa.

METHODS: We searched MEDLINE and PubMed from inception to 26 February 2020 for studies reporting measured and prescribed DNa. We analysed results reported in aggregate with random-effects meta-analysis. We analysed results reported by individual sample, using mixed-effects Bland-Altman analysis and linear regression. Pre-specified subgroup analyses included method of sodium measurement, dialysis machine manufacturer and proportioning method.

RESULTS: Seven studies, representing 908 dialysate samples from 10 HD facilities (range 16-133 samples), were identified. All but one were single-centre studies. Studies were of low to moderate quality. Overall, there was no statistically significant difference between measured and prescribed DNa {mean difference = 0.73 mmol/L [95% confidence interval (CI) -1.12 to 2.58; P = 0.44]} but variability across studies was substantial (I2 = 99.3%). Among individually reported samples (n = 295), measured DNa was higher than prescribed DNa by 1.96 mmol/L (95% CI 0.23-3.69) and the 95% limits of agreement ranged from -3.97 to 7.88 mmol/L. Regression analysis confirmed a strong relationship between prescribed and measured DNa, with a slope close to 1:1 (β = 1.16, 95% CI 1.06-1.27; P < 0.0001).

CONCLUSIONS: A limited number of studies suggest that, on average, prescribed and measured DNa are similar. However, between- and within-study differences were large. Further consideration of the precision of delivered DNa is required to inform rational prescribing.