Skip to main content

Hyponatremia and intensive care outcome


Disorders of sodium (Na+) and water homeostasis are common in hospitalised patients. Hyponatremia in particular has been associated with worse hospital outcome and length of stay [1]. We aimed to define the incidence of hyponatremia (serum Na+ ≤134 mmol/l) in our intensive care population and to determine whether it was associated with ICU outcome or length of stay.


Demographics, APACHE II score, outcome data and admission sodium were retrieved from the Ward Watcher system in the Victoria Infirmary ICU for 2,440 consecutive admissions from January 2005 to present. We divided patients into three groups depending on serum Na+ (≤134 mmol/l, 135 to 144 mmol/l, ≥145 mmol/l) and compared APACHE II score, length of stay and ICU outcome between patients with a low versus a normal serum Na+. Data were analysed using the chi-squared test, Student's t test and the Mann-Whitney test where appropriate.


Of the 2,440 patients studied, 1,993 had APACHE II data and serum Na+ recorded and so were included for analysis. In total, 453 patients (22.7%) had a serum Na+ ≤134 mmol/l and 1,388 patients (67.1%) had a serum Na+ of 135 to 144 mmol/l. Patients with a low Na+ had a higher mortality (OR = 1.48, 95% CI = 1.16 to 1.90, P 0.001), a higher APACHE II score (22 vs. 19, P 0.001) and higher mean age (60 years vs. 58 years, P 0.001) than patients with a normal serum Na+. Mean length of stay of patients with low serum Na+ was also longer (5.1 days vs. 4.6 days) although this was not statistically significant (P = 0.09).


In summary, hyponatremia is a useful index of severity of illness in our ICU population. Whether this is a direct adverse effect of low serum sodium levels, or if hyponatremia is simply a marker for 'sicker' patients, is not known.


  1. Asadollahi, et al.: Hyponatraemia as a risk factor for hospital mortality. QJM 2006, 99: 877-880. 10.1093/qjmed/hcl120

    Article  CAS  PubMed  Google Scholar 

Download references

Author information

Authors and Affiliations


Rights and permissions

This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated in a credit line to the data.

Reprints and Permissions

About this article

Cite this article

Dean, P., Docking, R., Govenden, D. et al. Hyponatremia and intensive care outcome. Crit Care 17 (Suppl 2), P443 (2013).

Download citation

  • Published:

  • DOI:


  • Serum Sodium Level
  • Hospital Outcome
  • Water Homeostasis
  • Consecutive Admission
  • High Apache