Supplementary Material for: Potassium Trajectories prior to Dialysis and Mortality following Dialysis Initiation in Patients with Advanced CKD

Introduction: Patients with advanced non-dialysis-dependent CKD (NDD-CKD) have a reduced ability for maintaining plasma potassium (K) in normal range. Deviation from normal plasma K ranges is associated with increased mortality; however, the average trajectory of plasma K over time in patients with advanced NDD-CKD and the outcomes associated with plasma K trajectory are unknown. Methods: We identified 34,167 US veterans with advanced NDD-CKD transitioning to dialysis between October 2007 and March 2015 with at least 1 K measurement each year over a 3-year period prior to dialysis transition (3-year prelude). The K trajectory defined as the change in K (slope) per year over the entire 3-year prelude was estimated using linear mixed-effects models. The association between unadjusted (crude) K slope (categorized as stable [−0.09 to 0.09 mEq/L/year], decreasing [≤−0.10 mEq/L/year], and increasing [≥0.10 mEq/L/year]) and time to all-cause and cardiovascular mortality during the 6 months following dialysis initiation was assessed using multivariable-adjusted survival models. Results: The crude and multivariable-adjusted K slopes (mean, 95% CI) over the 3-year prelude were 0.008 (0.0059, 0.0110) and −0.15 mEq/L/year (−0.19, −0.11), respectively. Decreasing K slope was associated with higher multivariable-adjusted risk of all-cause mortality (adjusted hazard ratio [95% CI] vs. stable K slope: 1.08 [1.00–1.17]). No association was observed between K slope and cardiovascular mortality. Discussion/Conclusion: The average intraindividual plasma K trajectory is remarkably stable in patients with advanced NDD-CKD. A decreasing K slope is associated with higher all-cause mortality risk.