title: Serum Potassium and Short-term Clinical Outcomes Among Hemodialysis Patients: Impact of the Long Interdialytic Interval.
abstract: BACKGROUND
  Hyperkalemia is common among hemodialysis patients and is associated with morbidity and mortality. The long interdialytic interval is likewise associated with adverse outcomes. However, the interplay among serum potassium, dialysis cycle phase, and clinical outcomes has not been examined.
  
  
  METHODS
  Retrospective observational study.
  
  
  METHODS
  52,734 patients receiving in-center hemodialysis at a large dialysis organization during 2010 and 2011 contributed 533,889 potassium measurements (230,634 on Monday; 285,522 on Wednesday; 17,733 on Friday).
  
  
  METHODS
  Serum potassium concentration, day of the week of potassium measurement.
  
  
  RESULTS
  Death, hospitalization, emergency department (ED) visit.
  
  
  RESULTS
  There was a significant association between higher serum potassium and risk of hospitalization within 96 hours that was of greater magnitude on Fridays (389 hospitalizations) than Mondays or Wednesdays (4,582 and 4,629 hospitalizations, respectively; P for interaction = 0.008). Serum potassium of 5.5 to <6.0 (vs the referent category of 4.0-<4.5 mEq/L) was associated with increased risk of hospitalization on Fridays, with an adjusted OR of 1.68 (95% CI, 1.22-2.30). However, serum potassium of 5.5 to <6.0 mEq/L was associated with only mild elevation of risk on Mondays and no significantly increased risk on Wednesdays (adjusted ORs of 1.12 [95% CI, 1.00-1.24] and 1.04 [95% CI, 0.94-1.16], respectively). Associations of elevated serum potassium (6.0-<6.5 mEq/L or greater) with death and ED visit were significant, but did not differ based on day of the week.
  
  
  CONCLUSIONS
  There were insufficient observations to detect effect modification by day of the week for deaths, ED visits, and specific causes of hospitalizations. Confounding may have influenced results.
  
  
  CONCLUSIONS
  Higher serum potassium is associated with increased short-term risk of hospitalization, ED visit, and death. The association between serum potassium and hospitalization risk is modified by day of the week, consistent with a contribution of accumulated potassium to adverse outcomes following the long interdialytic interval. Further work is needed to determine whether directed interventions ameliorate this risk.
authors.affiliation: DaVita Clinical Research, Minneapolis, MN. Electronic address: steven.brunelli@davita.com.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Brunelli
authors.affiliation: Relypsa Inc, Redwood City, CA.
authors.forename: Charles
authors.initials: C
authors.lastname: Du Mond
authors.affiliation: Relypsa Inc, Redwood City, CA; Department of Clinical Pharmacy, University of California San Francisco, San Francisco, CA.
authors.forename: Nina
authors.initials: N
authors.lastname: Oestreicher
authors.affiliation: Vifor Pharma, Glattbrugg, Switzerland.
authors.forename: Viatcheslav
authors.initials: V
authors.lastname: Rakov
authors.affiliation: Relypsa Inc, Redwood City, CA.
authors.forename: David M
authors.initials: DM
authors.lastname: Spiegel
mesh_terms: D000368:Aged; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D008875:Middle Aged; D011188:Potassium / Q000097:blood*; D006435:Renal Dialysis / Q000009:adverse effects / Q000379:methods*; D012189:Retrospective Studies; D018570:Risk Assessment; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D011188:Potassium
keywords: Hyperkalemia; emergency department visit; end-stage renal disease (ESRD); hemodialysis; hospitalization; long interdialytic interval; mortality; phase of dialytic cycle; potassium gradient; serum potassium