title: Postoperative hyponatremia predicts an increase in mortality and in-hospital complications after cardiac surgery.
abstract: BACKGROUND
  The association between postoperative hyponatremia (Na < 135 mEq/L) and outcomes after cardiac surgery has not been established. We studied the prevalence of postoperative hyponatremia and its effects on outcomes after cardiac surgery.
  
  
  METHODS
  We studied 4,850 patients who underwent cardiac surgery from 2002 to 2008. We used multivariable logistic and Cox regression analysis to study the association between postoperative hyponatremia and mortality, length of hospital stay (LOS), and complications.
  
  
  RESULTS
  Postoperative hyponatremia was present in 59%. Hyponatremic patients were older (mean ± SD, 62 ± 13 vs 61 ± 14 years, p = 0.001), had lower left ventricle ejection fraction (mean ± SD, 44% ± 16% vs 48% ± 13%, p < 0.001), higher mean pulmonary artery pressures (mean ± SD, 30 ± 11 vs 27 ± 9 mmHg, p < 0.001), lower glomerular filtration rate (mean ± SD, 72 ± 29 vs 74 ± 27 mg/min/1.73 m(2), p = 0.01), higher EuroSCORE (median, 15% vs 6%, p < 0.001), higher New York Heart Association class IV (31% vs 26%, p = 0.002), prevalence of COPD (23% vs 14%, p < 0.001), and peripheral vascular disease (16% vs 12%, p < 0.001). Hyponatremia increased overall (24% vs 18.2%, p < 0.001) and late mortality (18.6% vs 13.9%, p < 0.001) and length of stay (LOS; 11 vs 7 days, p < 0.001). Mortality increased with the severity of the hyponatremia. After adjusting for baseline and procedure variables, postoperative hyponatremia was associated with increase in mortality (hazard ratio 1.22, 95% CI 1.06-1.4, p = 0.004), LOS (multiplier 1.34, 95% CI 1.22-1.49, p < 0.001), infectious (odds ratio [OR] 2.32, 95% CI 1.48-3.62, p < 0.001), pulmonary (OR 1.82, 95% CI 1.49-2.21, p < 0.001), and renal failure complications (OR 2.46, 95% CI 1.58-3.81, p < 0.001) and need for dialysis (OR 3.66, 95% CI 1.72-7.79, p = 0.001).
  
  
  CONCLUSIONS
  Hyponatremia is common after cardiac surgery and is an independent predictor of increased mortality, length of hospital stay, and postoperative complications.
authors.affiliation: Division of Cardiac Surgery, Wexner Medical Center, The Ohio State University, Columbus, OH, USA. juan.crestanello@osumc.edu
authors.forename: Juan A
authors.initials: JA
authors.lastname: Crestanello
authors.forename: Gary
authors.initials: G
authors.lastname: Phillips
authors.forename: Michael S
authors.initials: MS
authors.lastname: Firstenberg
authors.forename: Chittoor
authors.initials: C
authors.lastname: Sai-Sudhakar
authors.forename: John
authors.initials: J
authors.lastname: Sirak
authors.forename: Robert
authors.initials: R
authors.lastname: Higgins
authors.forename: William T
authors.initials: WT
authors.lastname: Abraham
mesh_terms: D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D005260:Female; D005500:Follow-Up Studies; D006331:Heart Diseases / Q000601:surgery; D017052:Hospital Mortality / Q000639:trends; D006801:Humans; D007010:Hyponatremia / Q000453:epidemiology* / Q000209:etiology; D015994:Incidence; D007902:Length of Stay / Q000639:trends; D008297:Male; D008875:Middle Aged; D009820:Ohio / Q000453:epidemiology; D011183:Postoperative Complications / Q000453:epidemiology* / Q000209:etiology; D015995:Prevalence; D011379:Prognosis; D016016:Proportional Hazards Models; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors