Serum Potassium and Mortality Risk in Hemodialysis Patients: A Cohort Study
Esther de Rooij, Friedo W. Dekker, Saskia le Cessie, Ewout J. Hoorn, Johan W. de Fijter, Ellen K. Hoogeveen, Joost A. Bijlsma, M. Boekhout, Walther H. Boer, Paul J. M. van der Boog, H.R. Büller, Marjolijn van Buren, Frank de Charro, C.J. Doorenbos, Marinus A. van den Dorpel, A. van Es, Wouter J. Fagel, Geert W. Feith, C. W. H. de Fijter, L.A.M. Frenken, Willem S. de Grave, J.A.C.A. van Geelen, P. G. G. Gerlag, J.P.M.C. Gorgels, R. M. Huisman, Kitty J. Jager, Kim E. Jie, W.A.H. Koning–Mulder, M. I. Koolen, T.K. Kremer Hovinga, A. T. J. Lavrijssen, Antinus J. Luik, Jan van der Meulen, K. J. Parlevliet, M. H. M. Raasveld, Frank M. van der Sande, Marc Schonck, Macé M. Schuurmans, C. E. H. Siegert, Coen A. Stegeman, Paul E. Stevens, J.G.P. Thijssen, R. M. Valentijn, G Vastenburg, Cornelis A. Verburgh, H.H. Vincent, Piet Vos
Abstract
RATIONALE & OBJECTIVE: Both hypo- and hyperkalemia can cause fatal cardiac arrhythmias. Although predialysis serum potassium level is a known modifiable risk factor for death in patients receiving hemodialysis, especially for hypokalemia, this risk may be underestimated. Therefore, we investigated the relationship between predialysis serum potassium level and death in incident hemodialysis patients and whether there is an optimum level. STUDY DESIGN: Prospective multicenter cohort study. SETTING & PARTICIPANTS: 1,117 incident hemodialysis patients (aged >18 years) from the Netherlands Cooperative Study on the Adequacy of Dialysis-2 study were included and followed from their first hemodialysis treatment until death, transplantation, switch to peritoneal dialysis, or a maximum of 10 years. EXPOSURE: Predialysis serum potassium levels were obtained every 6 months and divided into 6 categories: ≤4.0 mmol/L, >4.0 mmol/L to ≤4.5 mmol/L, >4.5 mmol/L to ≤5.0 mmol/L, >5.0 mmol/L to ≤5.5 mmol/L (reference), >5.5 mmol/L to ≤6.0 mmol/L, and >6.0 mmol/L. OUTCOMES: 6-month all-cause mortality. ANALYTICAL APPROACH: Cox proportional hazards and restricted cubic spline analyses with time-dependent predialysis serum potassium levels were used to calculate the adjusted HRs for death. RESULTS: ). During the 10-year follow-up, 555 (50%) deaths were observed. Multivariable adjusted HRs for death according to the 6 potassium categories were as follows: 1.42 (95% CI, 1.01-1.99), 1.09 (95% CI, 0.82-1.45), 1.21 (95% CI, 0.94-1.56), 1 (reference), 0.95 (95% CI, 0.71-1.28), and 1.32 (95% CI, 0.97-1.81). LIMITATIONS: Shorter intervals between potassium measurements would have allowed for more precise mortality risk estimations. CONCLUSIONS: We found a U-shaped relationship between serum potassium level and death in incident hemodialysis patients. A low predialysis serum potassium level was associated with a 1.4-fold stronger risk of death than the optimal level of approximately 5.1 mmol/L. These results may imply the cautious use of potassium-lowering therapy and a potassium-restricted diet in patients receiving hemodialysis.