title: Preoperative hyponatremia predicts outcomes after cardiac surgery.
abstract: OBJECTIVE
  To study the effect of preoperative hyponatremia (Na <135 mEq/L) on outcomes after cardiac surgery.
  
  
  METHODS
  From 2002 to 2008, 4370 patients had cardiac surgery at our institution (CABG in 2238, valve in 597, CABG valve in 537, other in 998). The institution electronic medical records, STS database, and Social Security death index data were analyzed. The association of hyponatremia with mortality, hospital length of stay (LOS), and complications was analyzed using regression analysis.
  
  
  RESULTS
  Prevalence of hyponatremia was 21%. Patients with preoperative hyponatremia had lower left ventricular ejection fraction (39% ± 17% versus 46% ± 14%, P < 0.001) and glomerular filtration rate (69 ± 32 mg/min/1.73 m(2)versus 74 ± 27 mg/min/1.73 m(2), P < 0.001) and higher median EuroSCORE (19% versus 9%, P < 0.001), NYHA class 3-4 (77% versus 65%, P < 0.001), prevalence of chronic obstructive pulmonary disease (25% versus 18%, P < 0.001), and arteriopathy (20% versus 13%, P < 0.001). Hyponatremia was associated with increased early mortality (9% versus 4%, P < 0.001), late mortality (24% versus 16%, P < 0.001), and LOS (13 versus 8 d, P < 0.001). Mortality increased with the severity of hyponatremia. After adjusting for baseline and operative variables, hyponatremia was associated with increased hazard of mortality (hazard ratio [HR] 1.31, 95% confidence interval [CI] 1.14-1.52, P < 0.001), risk of early mortality (odds ratio [OR] 1.52, 95% CI 1.09-2.12, P < 0.001), late mortality (HR 1.37, 95% CI 1.16-1.62, P < 0.001), LOS (multiplier 1.26, 95% CI 1.15-1.39, P < 0.001), operative complications (OR 1.30, 95% CI 1.00-1.69, P = 0.051), and dialysis (OR 1.64, 95% CI 1.11-2.44, P = 0.013).
  
  
  CONCLUSIONS
  Preoperative hyponatremia is common, especially in high-risk patients. It is an independent risk factor for mortality, prolonged hospitalization, and complications after cardiac surgery.
authors: Division of Cardiac Surgery, Wexner Medical Center, The Ohio State University, Columbus, OH 43210, USA. juan.crestanello@osumc.edu
authors: Juan A
authors: JA
authors: Crestanello
authors: Gary
authors: G
authors: Phillips
authors: Michael S
authors: MS
authors: Firstenberg
authors: Chittoor
authors: C
authors: Sai-Sudhakar
authors: John
authors: J
authors: Sirak
authors: Robert
authors: R
authors: Higgins
authors: William T
authors: WT
authors: Abraham
mesh_terms: D000328:Adult; D000368:Aged; D006348:Cardiac Surgical Procedures / Q000009:adverse effects / Q000401:mortality*; D005260:Female; D006801:Humans; D007010:Hyponatremia / Q000150:complications*; D007902:Length of Stay; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D016896:Treatment Outcome