title: Electrolyte disorders and in-hospital mortality during prolonged heat periods: a cross-sectional analysis.
abstract: BACKGROUND
  Heat periods during recent years were associated with excess hospitalization and mortality rates, especially in the elderly. We intended to study whether prolonged warmth/heat periods are associated with an increased prevalence of disorders of serum sodium and potassium and an increased hospital mortality.
  
  
  METHODS
  In this cross-sectional analysis all patients admitted to the Department of Emergency Medicine of a large tertiary care facility between January 2009 and December 2010 with measurements of serum sodium were included. Demographic data along with detailed data on diuretic medication, length of hospital stay and hospital mortality were obtained for all patients. Data on daily temperatures (maximum, mean, minimum) and humidity were retrieved by Meteo Swiss.
  
  
  RESULTS
  A total of 22.239 patients were included in the study. 5 periods with a temperature exceeding 25 °C for 3 to 5 days were noticed and 2 periods with temperatures exceeding 25 °C for more than 5 days were noted. Additionally, 2 periods with 3 to 5 days with daily temperatures exceeding 30 °C were noted during the study period. We found a significantly increased prevalence of hyponatremia during heat periods. However, in the Cox regression analysis, prolonged heat was not associated with the prevalence of disorders of serum sodium or potassium. Admission during a heat period was an independent predictor for hospital mortality.
  
  
  CONCLUSIONS
  Although we found an increased prevalence of hyponatremia during heat periods, no convincing connection could be found for hypernatremia or disorders of serum potassium.
authors.affiliation: Department of Emergency Medicine, Inselspital, University Hospital Bern, Bern, Switzerland; Department of General Internal Medicine, Inselspital, University Hospital Bern, Bern, Switzerland.
authors.forename: Carmen A
authors.initials: CA
authors.lastname: Pfortmueller
authors.affiliation: Department of Respiratory and Critical Care Medicine, Otto Wagner Spital Vienna and Ludwig-Boltzmann Institute for COPD and Respiratory Epidemiology, Vienna, Austria.
authors.forename: Georg-Christian
authors.initials: GC
authors.lastname: Funk
authors.affiliation: Center for Laboratory Medicine, Inselspital, University Hospital Bern, Bern, Switzerland.
authors.forename: Alexander B
authors.initials: AB
authors.lastname: Leichtle
authors.affiliation: Center for Laboratory Medicine, Inselspital, University Hospital Bern, Bern, Switzerland.
authors.forename: Georg M
authors.initials: GM
authors.lastname: Fiedler
authors.affiliation: Department of Nephrology, Landeskrankenhaus Steyr, Steyr, Austria.
authors.forename: Christoph
authors.initials: C
authors.lastname: Schwarz
authors.affiliation: Department of Emergency Medicine, Inselspital, University Hospital Bern, Bern, Switzerland.
authors.forename: Aristomenis K
authors.initials: AK
authors.lastname: Exadaktylos
authors.affiliation: Department of Emergency Medicine, Inselspital, University Hospital Bern, Bern, Switzerland.
authors.forename: Gregor
authors.initials: G
authors.lastname: Lindner
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D004232:Diuretics / Q000008:administration & dosage / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D005260:Female; D017052:Hospital Mortality; D006760:Hospitalization / Q000706:statistics & numerical data; D006358:Hot Temperature; D006801:Humans; D006813:Humidity; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D016016:Proportional Hazards Models; D012621:Seasons; D013557:Switzerland / Q000453:epidemiology; D014883:Water-Electrolyte Imbalance / Q000401:mortality*
chemical_list: D004232:Diuretics