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Open Access Highly Accessed Research article

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

Marya D Zilberberg1*, Alex Exuzides2, James Spalding3, Aimee Foreman2, Alison Graves Jones2, Chris Colby2 and Andrew F Shorr4

Author Affiliations

1 Evi Med Research Group, LLC, Goshen, Massachusetts, USA

2 ICON Clinical Research, San Francisco, California, USA

3 Astellas Pharma US, Inc., Deerfield, Illinois, USA

4 Dept. of Pulmonary and Critical Care Medicine, Washington Hospital Center, Washington, District of Columbia, USA

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BMC Pulmonary Medicine 2008, 8:16  doi:10.1186/1471-2466-8-16

Published: 18 August 2008



Community-acquired (CAP) and nosocomial pneumonias contribute substantially to morbidity and hospital resource utilization. Hyponatremia, occurring in >1/4 of patients with CAP, is associated with greater disease severity and worsened outcomes.


To explore how hyponatremia is associated with outcomes in hospitalized patients with pneumonia, we analyzed a large administrative database with laboratory component from January 2004 to December 2005. Hyponatremia was defined as at least two [Na+] < 135 mEq/L within 24 hours of admission value.


Of 7,965 patients with pneumonia, 649 (8.1%) with hyponatremia were older (72.4 ± 15.7 vs. 68.0 ± 22.0, p < 0.01), had a higher mean Deyo-Charlson Comorbidity Index Score (1.7 ± 1.7 vs. 1.6 ± 1.6, p = 0.02), and higher rates of ICU (10.0% vs. 6.3%, p < 0.001) and MV (3.9% vs. 2.3%, p = 0.01) in the first 48 hours of hospitalization than patients with normal sodium. Hyponatremia was associated with an increased ICU (6.3 ± 5.6 vs. 5.3 ± 5.1 days, p = 0.07) and hospital lengths of stay (LOS, 7.6 ± 5.3 vs. 7.0 ± 5.2 days, p < 0.001) and a trend toward increased hospital mortality (5.4% vs. 4.0%, p = 0.1). After adjusting for confounders, hyponatremia was associated with an increased risk of ICU (OR 1.58, 95% CI 1.20–2.08), MV (OR 1.75 95% CI 1.13–2.69), and hospital death (OR 1.3, 95% CI 0.90–1.87) and with increases of 0.8 day to ICU and 0.3 day to hospital LOS, and over $1,300 to total hospital costs.


Hyponatremia is common among hospitalized patients with pneumonia and is associated with worsened clinical and economic outcomes. Studies in this large population are needed to explore whether prompt correction of [Na+] may impact these outcomes.