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

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

author email corresponding author email

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

Published:	18 August 2008

Abstract

Background

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.

Methods

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.

Results

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.

Conclusion

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.