title: Fluctuation of serum sodium and its impact on short and long-term mortality following acute pulmonary embolism.
abstract: BACKGROUND
  Baseline hyponatremia predicts acute mortality following pulmonary embolism (PE). The natural history of serum sodium levels after PE and the relevance to acute and long-term mortality after the PE is unknown.
  
  
  METHODS
  Clinical details of all patients (n = 1023) admitted to a tertiary institution from 2000-2007 with acute PE were retrieved retrospectively. Serum sodium results from days 1, 3-4, 5-6, and 7 of admission were pre-specified and recorded. We excluded 250 patients without day-1 sodium or had <1 subsequent sodium assessment, leaving 773 patients as the studied cohort. There were 605 patients with normonatremia (sodium≥135 mmol/L throughout admission), 57 with corrected hyponatremia (day-1 sodium<135 mmol/L, then normalized), 54 with acquired hyponatremia and 57 with persistent hyponatremia. Patients' outcomes were tracked from a state-wide death registry and analyses performed using multivariate-regression modelling.
  
  
  RESULTS
  Mean (±standard deviation) day-1 sodium was 138.2±4.3 mmol/L. Total mortality (mean follow-up 3.6±2.5 years) was 38.8% (in-hospital mortality 3.2%). There was no survival difference between studied (n = 773) and excluded (n = 250) patients. Day-1 sodium (adjusted hazard ratio [aHR] 0.89, 95% confidence interval [CI] 0.83-0.95, p = 0.001) predicted in-hospital death. Relative to normonatremia, corrected hyponatremia increased the risk of in-hospital death 3.6-fold (95% CI 1.20-10.9, p = 0.02) and persistent hyponatremia increased the risk 5.6-fold (95% CI 2.08-15.0, p = 0.001). Patients with either persisting or acquired hyponatremia had worse long-term survival than those who had corrected hyponatremia or had been normonatremic throughout (aHR 1.47, 95% CI 1.06-2.03, p = 0.02).
  
  
  CONCLUSIONS
  Sodium fluctuations after acute PE predict acute and long-term outcome. Factors mediating the correction of hyponatremia following acute PE warrant further investigation.
authors.affiliation: Cardiology Department, Concord Hospital, The University of Sydney, Sydney, Australia.
authors.forename: Austin Chin Chwan
authors.initials: AC
authors.lastname: Ng
authors.forename: Vincent
authors.initials: V
authors.lastname: Chow
authors.forename: Andy Sze Chiang
authors.initials: AS
authors.lastname: Yong
authors.forename: Tommy
authors.initials: T
authors.lastname: Chung
authors.forename: Leonard
authors.initials: L
authors.lastname: Kritharides
mesh_terms: D000208:Acute Disease; D000368:Aged; D001315:Australia / Q000453:epidemiology; D004232:Diuretics / Q000627:therapeutic use; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D010351:Patient Discharge / Q000706:statistics & numerical data; D011655:Pulmonary Embolism / Q000097:blood* / Q000188:drug therapy / Q000401:mortality*; D012720:Severity of Illness Index; D012964:Sodium / Q000097:blood*; D013997:Time Factors
chemical_list: D004232:Diuretics; D012964:Sodium