title: Predictors and outcome impact of perioperative serum sodium changes in a high-risk population.
abstract: BACKGROUND
  The perioperative period may be associated with a marked neurohumoral stress response, significant fluid losses, and varied fluid replacement regimes. Acute changes in serum sodium concentration are therefore common, but predictors and outcomes of these changes have not been investigated in a large surgical population.
  
  
  METHODS
  We carried out a retrospective cohort analysis of 27 068 in-patient non-cardiac surgical procedures in a tertiary teaching hospital setting. Data on preoperative conditions, perioperative events, hospital length of stay, and mortality were collected, along with preoperative and postoperative serum sodium measurements up to 7 days after surgery. Logistic regression was used to investigate the association between sodium changes and mortality, and to identify clinical characteristics associated with a deviation from baseline sodium >5 mmol litre(-1).
  
  
  RESULTS
  Changes in sodium concentration >5 mmol litre(-1) were associated with increased mortality risk (adjusted odds ratio 1.49 for a decrease, 3.02 for an increase). Factors independently associated with a perioperative decrease in serum sodium concentration >5 mmol litre(-1) included age >60, diabetes mellitus, and the use of patient-controlled opioid analgesia. Factors associated with a similar increase were preoperative oxygen dependency, mechanical ventilation, central nervous system depression, non-elective surgery, and major operative haemorrhage.
  
  
  CONCLUSIONS
  Maximum deviation from preoperative serum sodium value is associated with increased hospital mortality in patients undergoing in-patient non-cardiac surgery. Specific preoperative and perioperative factors are associated with significant serum sodium changes.
authors.affiliation: Division of Perioperative Care, Box 93, Addenbrooke's Hospital, Cambridge University Hospitals NHS Foundation Trust, Hills Road, Cambridge CB2 0QQ, UK john.klinck@addenbrookes.nhs.uk.
authors.forename: J
authors.initials: J
authors.lastname: Klinck
authors.affiliation: Division of Perioperative Care, Box 93, Addenbrooke's Hospital, Cambridge University Hospitals NHS Foundation Trust, Hills Road, Cambridge CB2 0QQ, UK.
authors.forename: L
authors.initials: L
authors.lastname: McNeill
authors.affiliation: Cambridge University Department of Public Health and Primary Care, Strangeways Research Laboratory, Worts Causeway, Cambridge CB1 8RN, UK.
authors.forename: E
authors.initials: E
authors.lastname: Di Angelantonio
authors.affiliation: Division of Perioperative Care, Box 93, Addenbrooke's Hospital, Cambridge University Hospitals NHS Foundation Trust, Hills Road, Cambridge CB2 0QQ, UK.
authors.forename: D K
authors.initials: DK
authors.lastname: Menon
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000378:metabolism; D059035:Perioperative Period; D012189:Retrospective Studies; D012964:Sodium / Q000097:blood*; D013514:Surgical Procedures, Operative / Q000401:mortality*
chemical_list: D012964:Sodium
keywords: hospital mortality; perioperative period; sodium