Impact of hyponatremia on mortality and morbidity in patients with COPD exacerbations

Hyponatremia is the most common electrolyte disorder in hospitalized patients, being associated with increased morbidity and mortality in different clinical conditions. However, the prevalence and impact of this electrolytic disorder in patients hospitalized for an exacerbation of COPD still remains unknown. The aim of the present study was to clarify these points. A total of 424 patients hospitalized due to a COPD exacerbation were consecutively included, showing a frequency of hyponatremia of 15.8% (hyposmolar in most cases). Even though patients with and without hyponatremia showed a similar age, comorbidities, lung function impairment, presence of previous exacerbations, hospitalizations, most of the comorbidities and the overall severity index (APACHE II), their clinical outcomes were worse. Indeed, their hospitalization length, mechanical ventilation requirements and deaths (both during admission and within the months following discharge) were higher than those of non-hyponatremic patients. A sodium threshold lower than 129.7 mEq/L exhibited the better discriminatory power for death prediction. We conclude that hyponatremia (especially if severe) is a predictive marker for a bad clinical course in COPD exacerbations and therefore, patients with this electrolyte abnormality should be carefully monitored.