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Eur J Endocrinol. 2016 Dec;175(6):499-507. Epub 2016 Sep 1.

Long-term outcome of profound hyponatremia: a prospective 12 months follow-up study.

Author information

EndocrinologyDiabetology and Metabolism, University Hospital Basel, Basel, Switzerland
Department of Clinical ResearchUniversity Hospital Basel, Basel, Switzerland.
EndocrinologyDiabetology and Metabolism, University Hospital Basel, Basel, Switzerland.
Division of EndocrinologyDiabetology and Metabolism, Medical University Clinic, Kantonsspital Aarau, Aarau, Switzerland.
NephrologyDialysis & Transplantation, Kantonsspital Aarau, Aarau, Switzerland.
Institute of Laboratory MedicineKantonsspital Aarau, Aarau, Switzerland.



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.


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.


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.


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.

[Indexed for MEDLINE]

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