Supplementary Material for: Serum Potassium, End-Stage Renal Disease and Mortality in Chronic Kidney Disease

<b><i>Background/Aims:</i></b> Hypokalemia and hyperkalemia are often noted in chronic kidney disease (CKD) patients, but their impact on mortality and end-stage renal disease (ESRD) is less well understood. We aimed at studying the associations between potassium disorders, and mortality and progression to ESRD in a CKD population. <b><i>Methods:</i></b> Using our electronic health record-based CKD registry, 36,359 patients with eGFR &lt;60 ml/min/1.73 m² and potassium levels measured from January 1, 2005 to September 15, 2009 were identified. We examined factors associated with hypokalemia (&lt;3.5 mmol/l) and hyperkalemia (&gt;5.0 mmol/l) using logistic regression models and associations between serum potassium levels (both as continuous and categorical variables) and all-cause mortality or ESRD using Cox-proportional hazards models. <b><i>Results:</i></b> Serum potassium &lt;3.5 mmol/l was noted among 3% and &gt;5.0 mmol/l among 11% of the study population. In the multivariable logistic regression analysis, lower eGFR, diabetes and use of ACE inhibitors or Angiotensin-Receptor Blockers were associated with higher odds of having hyperkalemia. Heart failure and African American race were factors associated with higher odds of hypokalemia. After adjustment for covariates including kidney function, serum potassium &lt;4.0 and &gt;5.0 mmol/l were significantly associated with increased mortality risk, but there was no increased risk for progression to ESRD. Time-dependent repeated measures analysis confirmed these findings. When potassium was examined as a continuous variable, there was a U-shaped association between serum potassium levels and mortality. <b><i>Conclusion:</i></b> In patients with stage 3-4 CKD, serum potassium levels &lt;4.0 and &gt;5.0 mmol/l are associated with higher mortality but not with ESRD.

<b><i>背景与目的：</i></b> 慢性肾脏病（chronic kidney disease, CKD）患者常出现低钾血症（hypokalemia）与高钾血症（hyperkalemia），但此类钾代谢异常对患者死亡率及终末期肾病（end-stage renal disease, ESRD）发生的影响尚不甚明确。本研究旨在探讨慢性肾脏病人群中钾代谢紊乱与全因死亡率、进展至终末期肾病之间的关联。<b><i>方法：</i></b> 依托基于电子健康档案的慢性肾脏病注册登记库，本研究筛选得到2005年1月1日至2009年9月15日期间确诊的36359例估算肾小球滤过率（estimated glomerular filtration rate, eGFR）<60 ml/min/1.73 m²且完成血清钾水平检测的慢性肾脏病患者。采用logistic回归模型（logistic regression models）分析与低钾血症（血清钾<3.5 mmol/L）、高钾血症（血清钾>5.0 mmol/L）相关的影响因素；同时采用Cox比例风险模型（Cox-proportional hazards models），分别以连续变量和分类变量形式评估血清钾水平与全因死亡率、终末期肾病进展的关联。<b><i>结果：</i></b> 本研究队列中，3%的患者血清钾水平<3.5 mmol/L，11%的患者血清钾水平>5.0 mmol/L。多因素logistic回归分析显示，更低的估算肾小球滤过率、糖尿病史以及血管紧张素转换酶抑制剂（ACE inhibitors）或血管紧张素Ⅱ受体拮抗剂（Angiotensin-Receptor Blockers）的使用，与高钾血症的发病风险升高显著相关；而心力衰竭史与非裔美国人种族则与低钾血症的发病风险升高相关。在校正包括肾功能在内的协变量后，血清钾<4.0 mmol/L及>5.0 mmol/L均与死亡率升高显著相关，但未观察到进展至终末期肾病的风险增加。时间依赖性重复测量分析验证了上述研究结果。当以连续变量形式分析血清钾水平时，其与死亡率呈U型关联。<b><i>结论：</i></b> 在3~4期慢性肾脏病患者中，血清钾水平<4.0 mmol/L及>5.0 mmol/L与更高的死亡率相关，但与终末期肾病进展无显著关联。