Associations between serum potassium variability and mortality in patients undergoing maintenance hemodialysis: a retrospective study

Dyskalemia are associated with an increased risk of mortality in patients undergoing maintenance hemodialysis (MHD). However, studies evaluating the impact of serum potassium variability on mortality in MHD patients are scarce. To investigate serum potassium variability and its association with prognosis in MHD patients, we conducted a retrospective study on maintenance hemodialysis patients from three campus of Renji Hospital between June 2018 and December 2022. The exposure of interest was serum potassium variability defined as the coefficient of variation of serum potassium levels (CVSP). Cox regression models and Kaplan-Meier survival analysis were used to assess the prognostic significance of serum potassium variability. In a subgroup analysis, the association between serum potassium variability and prognosis was investigated in patients within normal serum potassium concentration range. Total of 588 maintenance hemodialysis patients were included. During a median follow-up of 45 months (24, 54), 121 patients (20.6%) died. The survival analysis suggested significantly higher survival rates for both all-cause (p < 0.01) and cardiovascular (p < 0.01) death in patients in the highest group of CVSP (H-CVSP) compared with those in the the lowest group (L-CVSP). After adjustment, the all-cause mortality hazard ratio compared to L-CVSP was 2.17 [95% confidence interval (CI) 1.18, 3.97] for H-CVSP (p < 0.05) and was 2.53 [95%CI 1.03, 6.22] for cardiovascular mortality (p < 0.05). In the subgroup analysis, 493 patients (83.8%) presented normokalemia (the mean of serum potassium levels >= 3.5mmol/L and <= 5.0mmol/L) were included. Similar association was found between serum potassium variability and accumulated survival rates, and higher serum potassium variablity was remained an independent risk factor for cardiovascular mortality (2.69, 95% CI 1.07-6.78, p < 0.05) in patients within normal serum potassium concentration range. In conclusion, a higher serum potassium variability was associated with all-cause and cardiovascular mortality in maintenance haemodialysis patients, even in the normal range.