Lower- Versus Conventional-Sodium Dialysate and Left Ventricular Mass in Hemodialysis Patients: Causal Analyses of a Randomized Clinical Trial

AbstractRationale "Dialytic BP" (indicated by pre/post-dialysis blood pressure measurements), "Inter-dialytic BP" (indicated by home/ambulatory measurements), antihypertensive dose, and IDWG. In the structural model, "Fluid Volume" had a large effect on LVMI (standardized path coefficient 95% confidence intervals 0.51 0.35,0.67), and smaller ones on "Dialytic BP" and "Inter-dialytic BP" (respectively: 0.31 0.15,0.47, 0.22 0.02,0.41). "Dialytic BP" and "Inter-dialytic BP" had small-to-medium-sized effects on LVMI (respectively: 0.23 0.04,0.42, 0.22 0.07,0.37). Neither IDWG or antihypertensive dose affected LVMI. Allocation to lower dialysate Na+ had a large effect on IDWG (-0.37 -0.50,-0.24), a marginal effect on antihypertensive dose (-0.20 -0.41,0.02), but none on "Fluid Volume" or BP constructs. Limitations Allocation rather than the intervention itself; residual confounding from unrecorded intermediary outcomes. Conclusions Allocation to lower dialysate Na+ did not change LVMI because of insufficient effect upon its main causes, namely fluid volume and BP. Although it reduced IDWG and antihypertensive dose, these factors did not causally affect LVMI.