Mortality after Hospitalization with Mild, Moderate, and Severe Hyponatremia

doi:10.1016/j.amjmed.2009.01.027

The American Journal of Medicine

Volume 122, Issue 9, September 2009, Pages 857-865

https://doi.org/10.1016/j.amjmed.2009.01.027 Get rights and content

Abstract

Background

Hyponatremia is the most common electrolyte abnormality in hospitalized individuals.

Methods

To investigate the association between serum sodium concentration and mortality, we conducted a prospective cohort study of 98,411 adults hospitalized between 2000 and 2003 at 2 teaching hospitals in Boston, Massachusetts. The main outcome measures were in-hospital, 1-year, and 5-year mortality. Multivariable logistic regression and Cox proportional hazards models were used to compare outcomes in patients with varying degrees of hyponatremia against those with normal serum sodium concentration.

Results

Hyponatremia (serum sodium concentration <135 mEq/L) was observed in 14.5% of patients on initial measurement. Compared with patients with normonatremia (135-144 mEq/L), those with hyponatremia were older (67.0 vs 63.1 years, P <.001) and had more comorbid conditions (mean Deyo-Charlson Index 1.9 vs 1.4, P <.001). In multivariable-adjusted models, patients with hyponatremia had an increased risk of death in hospital (odds ratio 1.47, 95% confidence interval [CI], 1.33-1.62), at 1 year (hazard ratio 1.38, 95% CI, 1.32-1.46), and at 5 years (hazard ratio 1.25, 95% CI, 1.21-1.30). The increased risk of death was evident even in those with mild hyponatremia (130-134 mEq/L; odds ratio 1.37, 95% CI, 1.23-1.52). The relationship between hyponatremia and mortality was pronounced in patients admitted with cardiovascular disease, metastatic cancer, and those admitted for procedures related to the musculoskeletal system. Resolution of hyponatremia during hospitalization attenuated the increased mortality risk conferred by hyponatremia.

Conclusion

Hyponatremia, even when mild, is associated with increased mortality.

Section snippets

Source Population

We extracted administrative and laboratory data from individuals admitted to 2 academic teaching hospitals in Boston, Massachusetts. Brigham and Women's Hospital (BWH) is a 777-bed teaching hospital. Massachusetts General Hospital (MGH) is a 902-bed teaching hospital. The 2 hospitals provide primary as well as tertiary care to an ethnically and socioeconomically diverse population within eastern Massachusetts and the surrounding region.

Data Sources

Data on all patients admitted for at least 48 hours to BWH

Clinical Characteristics

Among 98,411 individuals admitted during the study period, hyponatremia (serum sodium concentration <135 mEq/L) was present on the first sodium determination in 14,290 (14.5%) and at some point during hospitalization in an additional 5093 (total, 19.7%). Hyponatremia on admission was mild (130-134 mEq/L) in the majority of patients (83.0%) and severe (<120) in only 0.2% (Table 1).

Hyperglycemia (glucose ≥200 mg/dL) was present in 15.8% of patients admitted with hyponatremia (glucose was measured

Discussion

The prevalence of hyponatremia (first measured serum sodium concentration <135 mEq/L) in individuals hospitalized for at least 2 days is approximately 13%. Our estimate is higher than the 5.5% prevalence reported in the 39-hospital study by Zilberberg et al,⁵ which included all admissions irrespective of length of stay. Anderson et al¹² found a prevalence of 2.4% when defining hyponatremia as serum sodium concentration <130 mEq/L; our results using this definition are similar. Our study

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La correlación entre la Na_p estimada por el monitor de HD 6008 CAREsystem de Fresenius y la medida por el laboratorio es buena, siendo mejor en las mediciones prediálisis. Nuevos estudios deberán comprobar la validez externa de estos resultados.
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The correlation between the _pNa estimated by Fresnius 6008 CAREsystem HD monitor and that measured by the laboratory is good, especially pre-dialysis measurements. Further studies should verify the external validity of these results.
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: Funding: Investigator-initiated grant from Astellas Pharma US, Inc.

: Conflict of Interest: Dr. Mount reported receiving lecture fees from Astellas Pharma, US, Inc. Astellas had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript.

: Authorship: Dr. Waikar had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

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Clinical research studyMortality after Hospitalization with Mild, Moderate, and Severe Hyponatremia

Abstract

Background

Methods

Results

Conclusion

Section snippets

Source Population

Data Sources

Clinical Characteristics

Discussion

Am J Med

J Clin Epidemiol

Am J Med

Am J Med

Am J Cardiol

J Am Coll Cardiol

Lancet

Am Heart J

Am J Kidney Dis

Am J Med

Am J Med

Brenner & Rector's the Kidney

Severe hyponatraemia in medical in-patients: aetiology, assessment and outcome

QJM

Characteristics and mortality of severe hyponatraemia—a hospital-based study

Clin Endocrinol (Oxf)

Epidemiology, clinical and economic outcomes of admission hyponatremia among hospitalized patients

Curr Med Res Opin

Advanced age, anticoagulation intensity, and risk for intracranial hemorrhage among patients taking warfarin for atrial fibrillation

Ann Intern Med

Validity of International Classification of Diseases, Ninth Revision, Clinical Modification Codes for Acute Renal Failure

J Am Soc Nephrol

Comparison of the Elixhauser and Charlson/Deyo methods of comorbidity measurement in administrative data

Med Care

Hyperglycemia-induced hyponatremia—calculation of expected serum sodium depression

N Engl J Med

Hyponatremia: a prospective analysis of its epidemiology and the pathogenetic role of vasopressin

Ann Intern Med

Hyperglycemia: an independent marker of in-hospital mortality in patients with undiagnosed diabetes

J Clin Endocrinol Metab

Hyponatremia and hospital outcomes among patients with pneumonia: a retrospective cohort study

BMC Pulm Med

Hyponatremia in community-acquired pneumonia

Am J Nephrol

Addition of serum sodium into the MELD score predicts waiting list mortality better than MELD alone

Liver Transpl

Clinical research study
Mortality after Hospitalization with Mild, Moderate, and Severe Hyponatremia