title: Long-term outcome of profound hyponatremia: a prospective 12 months follow-up study.
abstract: BACKGROUND
  Hyponatremia is the most common electrolyte abnormality in hospitalized patients and given its impact on mortality and morbidity, a relevant medical condition. Nevertheless, little is known about factors influencing long-term outcome.
  
  
  METHODS
  This is a prospective observational 12-month follow-up study of patients with profound hyponatremia (≤125 mmol/L) admitted to the emergency department of two tertiary care centers between 2011 and 2013. We analyzed the predictive value of clinical and laboratory parameters regarding the following outcomes: 1-year mortality, rehospitalization and recurrent profound hyponatremia.
  
  
  RESULTS
  Median (IQR) initial serum sodium (s-sodium) level of 281 included patients was 120 mmol/L (116-123). During the follow-up period, 58 (20.6%) patients died. The majority (56.2%) were rehospitalized at least once. Recurrent hyponatremia was observed in 42.7%, being profound in 16%. Underlying comorbidities, assessed by the Charlson Comorbidity Index, predicted 1-year mortality (odds ratio (OR) 1.43, 95% confidence interval (CI) 1.25-1.64, P < 0.001). Furthermore, 's-sodium level at admission' (OR 1.14, 95% CI 1.01-1.29, P = 0.036) and 'correction of hyponatremia' defined as s-sodium ≥135 mmol/L at discharge were associated with mortality (OR 0.47, 95% CI 0.23-0.94, P = 0.034). Mortality rate fell with decreasing baseline s-sodium levels and was lower in the hyponatremia category ≤120 mmol/L vs >120 mmol/L (14.8% and 27.8%, P < 0.01). Patients with s-sodium level ≤120 mmol/L were more likely to have drug-induced hyponatremia, whereas hypervolemic hyponatremia was more common in patients with s-sodium >120 mmol/L.
  
  
  CONCLUSIONS
  Hyponatremia is associated with a substantial 1-year mortality, recurrence and rehospitalization rate. The positive correlation of s-sodium and mortality emphasizes the importance of the underlying disease, which determines the outcome besides hyponatremia itself.
authors: EndocrinologyDiabetology and Metabolism, University Hospital Basel, Basel, Switzerland Bettina.winzeler@usb.ch.|Department of Clinical ResearchUniversity Hospital Basel, Basel, Switzerland.
authors: Bettina
authors: B
authors: Winzeler
authors: EndocrinologyDiabetology and Metabolism, University Hospital Basel, Basel, Switzerland.
authors: Nica
authors: N
authors: Jeanloz
authors: EndocrinologyDiabetology and Metabolism, University Hospital Basel, Basel, Switzerland.|Department of Clinical ResearchUniversity Hospital Basel, Basel, Switzerland.
authors: Nicole
authors: N
authors: Nigro
authors: EndocrinologyDiabetology and Metabolism, University Hospital Basel, Basel, Switzerland.|Department of Clinical ResearchUniversity Hospital Basel, Basel, Switzerland.
authors: Isabelle
authors: I
authors: Suter-Widmer
authors: Division of EndocrinologyDiabetology and Metabolism, Medical University Clinic, Kantonsspital Aarau, Aarau, Switzerland.|Department of Clinical ResearchUniversity Hospital Basel, Basel, Switzerland.
authors: Philipp
authors: P
authors: Schuetz
authors: EndocrinologyDiabetology and Metabolism, University Hospital Basel, Basel, Switzerland.
authors: Birsen
authors: B
authors: Arici
authors: Division of EndocrinologyDiabetology and Metabolism, Medical University Clinic, Kantonsspital Aarau, Aarau, Switzerland.|Department of Clinical ResearchUniversity Hospital Basel, Basel, Switzerland.
authors: Martina
authors: M
authors: Bally
authors: Division of EndocrinologyDiabetology and Metabolism, Medical University Clinic, Kantonsspital Aarau, Aarau, Switzerland.|Department of Clinical ResearchUniversity Hospital Basel, Basel, Switzerland.
authors: Claudine
authors: C
authors: Blum
authors: Department of Clinical ResearchUniversity Hospital Basel, Basel, Switzerland.|NephrologyDialysis & Transplantation, Kantonsspital Aarau, Aarau, Switzerland.
authors: Andreas
authors: A
authors: Bock
authors: Department of Clinical ResearchUniversity Hospital Basel, Basel, Switzerland.|Institute of Laboratory MedicineKantonsspital Aarau, Aarau, Switzerland.
authors: Andreas
authors: A
authors: Huber
authors: Division of EndocrinologyDiabetology and Metabolism, Medical University Clinic, Kantonsspital Aarau, Aarau, Switzerland.|Department of Clinical ResearchUniversity Hospital Basel, Basel, Switzerland.
authors: Beat
authors: B
authors: Mueller
authors: EndocrinologyDiabetology and Metabolism, University Hospital Basel, Basel, Switzerland.|Department of Clinical ResearchUniversity Hospital Basel, Basel, Switzerland.
authors: Mirjam
authors: M
authors: Christ-Crain
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007010:Hyponatremia / Q000097:blood / Q000175:diagnosis* / Q000401:mortality*; D008297:Male; D008875:Middle Aged; D009026:Mortality / Q000639:trends; D010359:Patient Readmission / Q000639:trends*; D011446:Prospective Studies; D012008:Recurrence; D013997:Time Factors; D016896:Treatment Outcome