Abstract
BackgroundAbnormal serum potassium concentration has been suggested as a risk factor for mortality in patients undergoing dialysis patients. We investigated the impact of serum potassium levels on survival according to dialysis modality.MethodsA nationwide, prospective, observational cohort study for end stage renal disease patients has been ongoing in Korea since August 2008. Our analysis included patients whose records contained data regarding serum potassium levels. The relationship between serum potassium and mortality was analyzed using competing risk regression.ResultsA total of 3,230 patients undergoing hemodialysis (HD, 64.3%) or peritoneal dialysis (PD, 35.7%) were included. The serum potassium level was significantly lower (P < 0.001) in PD (median, 4.5 mmol/L; interquartile range, 4.0–4.9 mmol/L) than in HD patients (median, 4.9 mmol/L; interquartile range, 4.5–5.4 mmol/L). During 4.4 ± 1.7 years of follow-up, 751 patients (23.3%) died, mainly from cardiovascular events (n = 179) and infection (n = 120). In overall, lower serum potassium level less than 4.5 mmol/L was an independent risk factor for mortality after adjusting for age, comorbidities, and nutritional status (sub-distribution hazard ratio, 1.30; 95% confidence interval 1.10–1.53; P = 0.002). HD patients showed a U-shaped survival pattern, suggesting that both lower and higher potassium levels were deleterious, although insignificant. However, in PD patients, only lower serum potassium level (<4.5 mmol/L) was an independent predictor of mortality (sub-distribution hazard ratio, 1.35; 95% confidence interval 1.00–1.80; P = 0.048).ConclusionLower serum potassium levels (<4.5 mmol/L) occur more commonly in PD than in HD patients. It represents an independent predictor of survival in overall dialysis, especially in PD patients. Therefore, management of dialysis patients should focus especially on reducing the risk of hypokalemia, not only that of hyperkalemia.
Highlights
Patients with renal impairment have a high risk of potassium imbalance
A total of 3,230 patients were included in the analysis, comprising 2,078 HD patients and 1,152 peritoneal dialysis (PD) patients
In PD patients, the overall distribution of serum potassium levels was shifted to the left, and the mean level was significantly lower than that of HD patients (PD: 4.5 ± 0.6 mmol/L; HD: 4.9 ± 0.7 mmol/L; P < 0.001)
Summary
Patients with renal impairment have a high risk of potassium imbalance. Dyskalemia, both hyperkalemia and hypokalemia, can be responsible for the high prevalence of cardiovascular disease and even sudden death in dialysis patients by causing life-threatening cardiac arrhythmias. The Dialysis Outcomes and Practice Patterns Study database revealed that 6.3–20.0% of HD patients had serum potassium levels of more than 6 mmol/L at pre-dialysis [4]. This wide range can be attributed to ethnic differences. A recent study showed lower serum potassium level is related to infectious-caused mortality in PD patients [12]. We investigated the impact of serum potassium levels on survival according to dialysis modality.
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