P1445ESPECIALLY HYPOKALEMIA IS A RISK FACTOR FOR ALL-CAUSE MORTALITY IN INCIDENT HEMODIALYSIS PATIENTS

Abstract Background and Aims Both hypo- and hyperkalemia can potentially induce fatal cardiac arrhythmias in the general population. However, little is known about the effect of potassium as a modifiable risk factor in hemodialysis (HD) patients. Therefore, we investigated the relation between serum potassium level and all-cause mortality in incident HD patients and whether there is an optimum serum potassium level to pursue. Method All incident HD patients (>18 y) from the Netherlands Cooperative Study on the Adequacy of Dialysis (NECOSAD), a prospective multi-center cohort study, were included. These patients were followed from the start of their first dialysis treatment until death, transplantation or a maximum of 2 years. Serum potassium levels were obtained at fixed 6-month time intervals and divided into six categories: ≤ 4.0, > 4.0 - ≤ 4.5, > 4.5 - ≤ 5.0, > 5.0 - ≤ 5.5 (reference), > 5.5 - ≤ 6.0 and > 6.0 mmol/L. Using a Cox proportional-hazards model with serum potassium category as a time-dependent variable, hazard ratios (HR) for all-cause mortality were calculated, adjusted for baseline age, sex, current smoking, diabetes and residual kidney function. Results In total, 1278 HD patients were included. At baseline, mean (±SD) age was 64 (±14) years, 60% were men, 23% were current smokers, 21% had diabetes and the median (interquartile range) residual kidney function was 3.0 (1.5-4.8) ml/min/1.73m2. Mean (±SD) serum potassium level was 4.8 (±0.8) mmol/L. The prevalence of the six potassium categories was: 10%, 19%, 26%, 22%, 15% and 8%, respectively. A total of 298 (23%) deaths was observed during 2 years of follow-up. After multivariable adjustment the HR (95% CI) for any death according to the six potassium categories were: 2.5 (1.5-4.3), 1.9 (1.2-3.0), 1.6 (1.0-2.5), 1 (reference), 1.3 (0.8-2.2) and 1.7 (1.0-3.0). Conclusion We found a U-shaped relation between serum potassium and all-cause mortality in incident hemodialysis patients. Especially, low serum potassium was a 2.5-fold stronger risk factor for all-cause mortality compared to normal serum potassium. Our results indicate an optimum serum potassium level between 5.0 - 5.5 mmol/L, emphasizing that potassium lowering therapy should be used with caution in hemodialysis patients.