Impact of hospital-associated hyponatremia on selected outcomes.
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.
St Michael's Hospital and University of Toronto, and Keenan Research Centre in the Li Ka Shing Knowledge Institute of St Michael's Hospital, Toronto, Ontario, Canada.
Ron
R
Wald
Bertrand L
BL
Jaber
Lori Lyn
LL
Price
Ashish
A
Upadhyay
Nicolaos E
NE
Madias
D000046:Academic Medical Centers / Q000706:statistics & numerical data*; D000368:Aged; D002423:Cause of Death / Q000639:trends; D005260:Female; D017052:Hospital Mortality / Q000639:trends; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007010:Hyponatremia / Q000097:blood / Q000453:epidemiology / Q000209:etiology*; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D008404:Massachusetts / Q000453:epidemiology; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D012189:Retrospective Studies; D012307:Risk Factors; D012964:Sodium / Q000097:blood
D012964:Sodium