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.
Wald
Ron
R
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.
Jaber
Bertrand L
BL
Price
Lori Lyn
LL
Upadhyay
Ashish
A
Madias
Nicolaos E
NE
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