title: Preoperative abnormalities in serum sodium concentrations are associated with higher in-hospital mortality in patients undergoing major surgery.
abstract: BACKGROUND
  Abnormal serum sodium concentrations are common in patients presenting for surgery. It remains unclear whether these abnormalities are independent risk factors for postoperative mortality.
  
  
  METHODS
  This is a secondary analysis of the European Surgical Outcome Study (EuSOS) that provided data describing 46 539 patients undergoing inpatient non-cardiac surgery. Patients were included in this study if they had a recorded value of preoperative serum sodium within the 28 days immediately before surgery. Data describing preoperative risk factors and serum sodium concentrations were analysed to investigate the relationship with in-hospital mortality using univariate and multivariate logistic regression techniques.
  
  
  RESULTS
  Of 35 816 (77.0%) patients from the EuSOS database, 21 943 (61.3%) had normal values of serum sodium (138-142 mmol litre(-1)) before surgery, 8538 (23.8%) had hyponatraemia (serum sodium ≤137 mmol litre(-1)) and 5335 (14.9%) had hypernatraemia (serum sodium ≥143 mmol litre(-1)). After adjustment for potential confounding factors, moderate to severe hypernatraemia (serum sodium concentration ≥150 mmol litre(-1)) was independently associated with mortality [odds ratio 3.4 (95% confidence interval 2.0-6.0), P<0.0001]. Hyponatraemia was not associated with mortality.
  
  
  CONCLUSIONS
  Preoperative abnormalities in serum sodium concentrations are common, and hypernatraemia is associated with increased mortality after surgery. Abnormalities of serum sodium concentration may be an important biomarker of perioperative risk resulting from co-morbid disease.
authors.affiliation: Anaesthesia and Intensive Care, St George's Hospital and St George's University of London, London, UK mcecconi@sgul.ac.uk.
authors.forename: M
authors.initials: M
authors.lastname: Cecconi
authors.affiliation: Center for Medical Statistics, Informatics, and Intelligent Systems.
authors.forename: H
authors.initials: H
authors.lastname: Hochrieser
authors.affiliation: Department of Anaesthesia and Intensive Care and Institute of Clinical Sciences Malmö, Lund University, Lund, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Chew
authors.affiliation: Anaesthesia and Critical Care Medicine, University of Southampton, Southampton, UK.
authors.forename: M
authors.initials: M
authors.lastname: Grocott
authors.affiliation: Department of Anaesthesiology, University of Bonn, Bonn, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Hoeft
authors.affiliation: Intensive Care Unit, Ghent University Hospital, Ghent, Belgium.
authors.forename: A
authors.initials: A
authors.lastname: Hoste
authors.affiliation: Department of Anaesthesia and Intensive Care, Haukeland University Hospital, Bergen 5021, Norway.
authors.forename: I
authors.initials: I
authors.lastname: Jammer
authors.affiliation: Center for Medical Statistics, Informatics, and Intelligent Systems.
authors.forename: M
authors.initials: M
authors.lastname: Posch
authors.affiliation: Clinical Department of General Anaesthesiology, Emergency- and Intensive Care Medicine, Department of Anaesthesiology and Intensive Care Medicine, LKH - University Hospital of Graz, Medical University of Graz, Austria.
authors.forename: P
authors.initials: P
authors.lastname: Metnitz
authors.affiliation: Department of Surgical Sciences and Integrated Diagnostics, IRCCS San Martino IST, University of Genoa, Genoa, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Pelosi
authors.affiliation: Hospital de São José, Centro Hospitalar de Lisboa Central, EPE, UCINC, Lisbon, Portugal.
authors.forename: R
authors.initials: R
authors.lastname: Moreno
authors.affiliation: Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK.
authors.forename: R M
authors.initials: RM
authors.lastname: Pearse
authors.affiliation: Department of Intensive Care, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium.
authors.forename: J L
authors.initials: JL
authors.lastname: Vincent
authors.affiliation: Anaesthesia and Intensive Care, St George's Hospital and St George's University of London, London, UK.
authors.forename: A
authors.initials: A
authors.lastname: Rhodes
mesh_terms: D000368:Aged; D015897:Comorbidity; D005060:Europe / Q000453:epidemiology; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D006955:Hypernatremia / Q000097:blood / Q000453:epidemiology*; D007010:Hyponatremia / Q000097:blood / Q000453:epidemiology*; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011183:Postoperative Complications / Q000097:blood / Q000453:epidemiology*; D057234:Preoperative Period; D011446:Prospective Studies; D012189:Retrospective Studies; D012307:Risk Factors; D012964:Sodium / Q000097:blood; D013514:Surgical Procedures, Operative / Q000706:statistics & numerical data*
chemical_list: D012964:Sodium
keywords: high-risk surgery; hypernatraemia; hyponatraemia; perioperative medicine