Impact of hospital-associated hyponatremia on selected outcomes

Arch Intern Med. 2010 Feb 8;170(3):294-302. doi: 10.1001/archinternmed.2009.513.


Background: Hyponatremia is the most common electrolyte disorder encountered in hospitalized patients.

Methods: We evaluated whether hospital-associated hyponatremia has an independent effect on all-cause mortality, hospital length of stay (LOS), and patient disposition. This cohort study included all adult hospitalizations at an academic medical center occurring between 2000-2007 for which an admission serum sodium concentration ([Na(+)]) was available (N = 53 236). We examined community-acquired hyponatremia (admission serum [Na(+)], <138 mEq/L [to convert to millimoles per liter, multiply by 1.0]), hospital-aggravated hyponatremia (community-acquired hyponatremia complicated by worsening in serum [Na(+)]), and hospital-acquired hyponatremia (nadir serum [Na(+)], <138 mEq/L with a normal admission serum [Na(+)]). The independent associations of these hyponatremic presentations with in-hospital mortality, LOS, and patient disposition were evaluated using generalized estimating equations adjusted for age, sex, race, admission service, and Deyo-Charlson Comorbidity Index score.

Results: Community-acquired hyponatremia occurred in 37.9% of hospitalizations and was associated with adjusted odds ratios (ORs) of 1.52 (95% confidence interval [CI], 1.36-1.69) for in-hospital mortality and 1.12 (95% CI, 1.08-1.17) for discharge to a short- or long-term care facility and a 14% (95% CI, 11%-16%) adjusted increase in LOS. Hospital-acquired hyponatremia developed in 38.2% of hospitalizations longer than 1 day in which initial serum [Na(+)] was 138 to 142 mEq/L. Hospital-acquired hyponatremia was associated with adjusted ORs of 1.66 (95% CI, 1.39-1.98) for in-hospital mortality and 1.64 (95% CI, 1.55-1.74) for discharge to a facility and a 64% (95% CI, 60%-68%) adjusted increase in LOS. The strength of these associations tended to increase with hyponatremia severity.

Conclusions: Hospital-associated hyponatremia is a common occurrence. All forms of hyponatremia are independently associated with in-hospital mortality and heightened resource consumption.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Academic Medical Centers / statistics & numerical data*
  • Aged
  • Cause of Death / trends
  • Female
  • Hospital Mortality / trends
  • Hospitalization / statistics & numerical data*
  • Humans
  • Hyponatremia / blood
  • Hyponatremia / epidemiology
  • Hyponatremia / etiology*
  • Length of Stay / statistics & numerical data
  • Male
  • Massachusetts / epidemiology
  • Middle Aged
  • Outcome Assessment, Health Care*
  • Retrospective Studies
  • Risk Factors
  • Sodium / blood


  • Sodium