title: Low Serum Potassium Levels Increase the Infectious-Caused Mortality in Peritoneal Dialysis Patients: A Propensity-Matched Score Study.
abstract: OBJECTIVE
  Hypokalemia has been consistently associated with high mortality rate in peritoneal dialysis. However, studies investigating if hypokalemia is acting as a surrogate marker of comorbidities or has a direct effect in the risk for mortality have not been studied. Thus, the aim of this study was to analyze the effect of hypokalemia on overall and cause-specific mortality.
  
  
  METHODS
  This is an analysis of BRAZPD II, a nationwide prospective cohort study. All patients on PD for longer than 90 days with measured serum potassium levels were used to verify the association of hypokalemia with overall and cause-specific mortality using a propensity match score to reduce selection bias. In addition, competing risks were also taken into account for the analysis of cause-specific mortality.
  
  
  RESULTS
  There was a U-shaped relationship between time-averaged serum potassium and all-cause mortality of PD patients. Cardiovascular disease was the main cause of death in the normokalemic group with 133 events (41.8%) followed by PD-non related infections, n=105 (33.0%). Hypokalemia was associated with a 49% increased risk for CV mortality after adjustments for covariates and the presence of competing risks (SHR 1.49; CI95% 1.01-2.21). In contrast, in the group of patients with K <3.5 mEq/L, PD-non related infections were the main cause of death with 43 events (44.3%) followed by cardiovascular disease (n=36; 37.1%). For PD-non related infections the SHR was 2.19 (CI95% 1.52-3.14) while for peritonitis was SHR 1.09 (CI95% 0.47-2.49).
  
  
  CONCLUSIONS
  Hypokalemia had a significant impact on overall, cardiovascular and infectious mortality even after adjustments for competing risks. The causative nature of this association suggested by our study raises the need for intervention studies looking at the effect of potassium supplementation on clinical outcomes of PD patients.
authors.affiliation: School of Medicine, Pontifícia Universidade Católica do Paraná (PUCPR), Curitiba, Brazil.
authors.forename: Silvia Carreira
authors.initials: SC
authors.lastname: Ribeiro
authors.affiliation: Graduate Program in Medicine and Health Sciences, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, Brazil.
authors.forename: Ana Elizabeth
authors.initials: AE
authors.lastname: Figueiredo
authors.affiliation: School of Medicine, UNESP, Botucatu, Brazil.
authors.forename: Pasqual
authors.initials: P
authors.lastname: Barretti
authors.affiliation: School of Medicine, Pontifícia Universidade Católica do Paraná (PUCPR), Curitiba, Brazil.
authors.forename: Roberto
authors.initials: R
authors.lastname: Pecoits-Filho
authors.affiliation: School of Medicine, Pontifícia Universidade Católica do Paraná (PUCPR), Curitiba, Brazil.
authors.forename: Thyago Proenca
authors.initials: TP
authors.lastname: de Moraes
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001938:Brazil / Q000453:epidemiology; D002423:Cause of Death; D015897:Comorbidity; D005260:Female; D006801:Humans; D007008:Hypokalemia / Q000097:blood*; D007239:Infections / Q000453:epidemiology / Q000209:etiology* / Q000401:mortality*; D008297:Male; D008875:Middle Aged; D063868:Patient Outcome Assessment; D010530:Peritoneal Dialysis / Q000009:adverse effects*; D011188:Potassium / Q000097:blood*; D057216:Propensity Score; D011446:Prospective Studies
chemical_list: D011188:Potassium