Comparison of Prescribed and Measured Dialysate Sodium: A Quality Improvement Project

Abstract

Background: There is controversy regarding the optimal dialysate sodium concentration for hemodialysis patients. Dialysate sodium concentrations of 134 to 138 mEq/L may decrease interdialytic weight gain and improve hypertension control, whereas a higher dialysate sodium concentration may offer protection to patients with low serum sodium concentrations and hypotension. We conducted a quality improvement project to explore the hypothesis that prescribed and delivered dialysate sodium concentrations may differ significantly.

Study design: Cross-sectional quality improvement project.

Setting & participants: 333 hemodialysis treatments in 4 facilities operated by Dialysis Clinic, Inc.

Quality improvement plan: Measure dialysate sodium to assess the relationships of prescribed and measured dialysate sodium concentrations.

Outcomes: Magnitude of differences between prescribed and measured dialysate sodium concentrations.

Measurements: Dialysate sodium measured pre- and late dialysis.

Results: The least square mean of the difference between prescribed minus measured dialysate sodium concentration was -2.48 (95% CI, -2.87 to -2.10) mEq/L. Clinics with a greater number of different dialysate sodium prescriptions (clinic 1, n=8; clinic 2, n=7) and that mixed dialysate concentrates on site had greater differences between prescribed and measured dialysate sodium concentrations. Overall, 57% of measured dialysate sodium concentrations were within ±2 mEq/L of the prescribed dialysate sodium concentration. Differences were greater at higher prescribed dialysate sodium concentrations.

Limitations: We only studied 4 facilities and dialysate delivery machines from 2 manufacturers. Because clinics using premixed dialysate used the same type of machine, we were unable to independently assess the impact of these factors. Pressures in dialysate delivery loops were not measured.

Conclusions: There were significant differences between prescribed and measured dialysate sodium concentrations. This may have beneficial or deleterious effects on clinical outcomes, as well as confound results from studies assessing the relationships of dialysate sodium concentrations to outcomes. Additional studies are needed to identify factors that contribute to differences between prescribed and measured dialysate sodium concentrations. Quality assurance and performance improvement (QAPI) programs should include measurements of dialysate sodium.

Keywords: Prescribed dialysate sodium; delivered dialysate sodium; hemodialysis; measured dialysate sodium; ordered dialysate sodium; quality assurance; quality improvement; renal replacement therapy (RRT).