Outcomes of Adopting a Higher Versus Lower Concentration of Hemodialysate Magnesium as a Center-Wide Policy (Dial-Mag): A Clinical Research Protocol of a Pragmatic, Registry-Based, Cluster Randomized Trial.

Background: In individuals receiving hemodialysis, lower serum magnesium concentrations are associated with a higher risk of death and cardiovascular disease and more discomfort from muscle cramps. Small trials suggest that increasing serum magnesium by using a higher concentration of dialysate magnesium may be beneficial. This protocol outlines a large, randomized trial examining the effects of adopting a high versus low concentration of dialysate magnesium as a hemodialysis center-wide policy on the risk of mortality, major adverse cardiovascular events, and the burden of muscle cramps. Objective: To determine whether implementing a dialysate magnesium concentration of 0.75 mmol/L versus ≤ 0.5 mmol/L as a hemodialysis center-wide policy, for up to 4 years, affects (1) the rate of all-cause mortality or major cardiovascular-related hospitalizations or (2) the level of discomfort individuals experience from muscle cramps. Design: Pragmatic, 2-arm, parallel-group, registry-based, open-label, 2-sided superiority cluster randomized trial. Hemodialysis centers were randomly allocated (1:1) to one of the 2 arms. The assignment was constrained by five center-level prognostic factors and stratified by province. Setting: 137 hemodialysis centers in four Canadian provinces-Ontario, British Columbia, Alberta, and Manitoba. The trial period is from April 4, 2022, to March 31, 2026. Outcomes will be analyzed after March 31, 2026, using provincial health care databases and self-reported questionnaires. Participants: Individuals who received maintenance hemodialysis at participating centers during the trial period. Intervention: Use of a dialysate magnesium concentration of either 0.75 mmol/L or ≤ 0.5 mmol/L as a center-wide policy during the trial period. Measurements: The two primary outcomes are (1) a composite of all-cause mortality or major cardiovascular-related hospitalization (a hospital admission with myocardial infarction, congestive heart failure, or ischemic stroke) recorded in large health care databases and (2) self-reported muscle cramps collected from questionnaires. Methods: Using an intent-to-treat approach, the intervention effect on the instantaneous rate of the primary composite outcome will be analyzed using a stratified Cox proportional hazards model accounting for center-level clustering. The observation time will be censored for provincial emigration or the trial end date. Self-reported muscle cramps will be analyzed using a cumulative link (proportional odds) model. All models will be stratified by province and adjusted for the covariates used to constrain randomization. Limitations: The trial start date was delayed in some centers due to post-pandemic supply disruptions (including discontinued dialysate formulations); however, all centers secured dialysate concentrates in alignment with the trial-allocated magnesium level. Conclusions: The results of this pragmatic trial will inform center-wide policy on the optimal dialysate magnesium concentration for patient health. Trial Registration: www.clinicaltrials.gov; identifier: NCT04079582.