Serum potassium levels and its variability in incident peritoneal dialysis patients: associations with mortality.
BACKGROUND
Abnormal serum potassium is associated with an increased risk of mortality in dialysis patients. However, the impacts of serum potassium levels on short- and long-term mortality and association of potassium variability with death in peritoneal dialysis (PD) patients are uncertain.


METHODS
We examined mortality-predictability of serum potassium at baseline and its variability in PD patients treated in our center January 2006 through December 2010 with follow-up through December 2012. The hazard ratios (HRs) were used to assess the relationship between baseline potassium levels and short-term (≤1 year) as well as long-term (>1 year) survival. Variability of serum potassium was defined as the coefficient of variation of serum potassium (CVSP) during the first year of PD.


RESULTS
A total of 886 incident PD patients were enrolled, with 248 patients (27.9%) presented hypokalemia (serum potassium <3.5 mEq/L). During a median follow-up of 31 months (range: 0.5-81.0 months), adjusted all-cause mortality hazard ratio (HR) and 95% confidence interval (CI) for baseline serum potassium of <3.0, 3.0 to <3.5, 3.5 to <4.0, 4.5 to <5.0, and ≥5.0 mEq/L, compared with 4.0 to <4.5 (reference), were 1.79 (1.02-3.14), 1.15 (0.72-1.86), 1.31 (0.82-2.08), 1.33 (0.71-2.48), 1.28 (0.53-3.10), respectively. The increased risk of lower potassium with mortality was evident during the first year of follow-up, but vanished thereafter. Adjusted all-cause mortality HR for CVSP increments of 7.5% to <12.0%; 12.0% to <16.7% and ≥16.7%, compared with <7.5% (reference), were 1.35 (0.67-2.71), 2.00 (1.05-3.83) and 2.18 (1.18-4.05), respectively. Similar association was found between serum potassium levels and its variability and cardiovascular mortality.


CONCLUSIONS
A lower serum potassium level was associated with all-cause and cardiovascular mortality during the first year of follow-up in incident PD patients. In addition, higher variability of serum potassium levels conferred an increased risk of death in this population.
Department of Nephrology, The First Affiliated Hospital, Sun Yat-sen University, Key Laboratory of Nephrology, Ministry of Health of China, Guangzhou, China.
Qingdong
Q
Xu
Department of Nephrology, The First Affiliated Hospital, Sun Yat-sen University, Key Laboratory of Nephrology, Ministry of Health of China, Guangzhou, China.
Fenghua
F
Xu
Department of Nephrology, The First Affiliated Hospital, Sun Yat-sen University, Key Laboratory of Nephrology, Ministry of Health of China, Guangzhou, China.
Li
L
Fan
Department of Nephrology, The First Affiliated Hospital, Sun Yat-sen University, Key Laboratory of Nephrology, Ministry of Health of China, Guangzhou, China.
Liping
L
Xiong
Department of Nephrology, The First Affiliated Hospital, Sun Yat-sen University, Key Laboratory of Nephrology, Ministry of Health of China, Guangzhou, China.
Huiyan
H
Li
Department of Nephrology, The First Affiliated Hospital, Sun Yat-sen University, Key Laboratory of Nephrology, Ministry of Health of China, Guangzhou, China.
Shirong
S
Cao
Department of Nephrology, The First Affiliated Hospital, Sun Yat-sen University, Key Laboratory of Nephrology, Ministry of Health of China, Guangzhou, China.
Xiaoyan
X
Lin
Department of Nephrology, The First Affiliated Hospital, Sun Yat-sen University, Key Laboratory of Nephrology, Ministry of Health of China, Guangzhou, China.
Zhihua
Z
Zheng
Department of Nephrology, The First Affiliated Hospital, Sun Yat-sen University, Key Laboratory of Nephrology, Ministry of Health of China, Guangzhou, China.
Xueqing
X
Yu
Department of Nephrology, The First Affiliated Hospital, Sun Yat-sen University, Key Laboratory of Nephrology, Ministry of Health of China, Guangzhou, China.
Haiping
H
Mao
D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D002318:Cardiovascular Diseases / Q000097:blood / Q000209:etiology / Q000401:mortality*; D005260:Female; D006801:Humans; D007008:Hypokalemia / Q000097:blood / Q000209:etiology / Q000401:mortality*; D008297:Male; D008875:Middle Aged; D009026:Mortality; D010530:Peritoneal Dialysis / Q000009:adverse effects*; D011188:Potassium / Q000097:blood*; D016016:Proportional Hazards Models; D018709:Statistics, Nonparametric; D016019:Survival Analysis
D011188:Potassium