Impact of hyponatremia and the syndrome of inappropriate antidiuresis on mortality in elderly patients with aspiration pneumonia.

Abstract

BACKGROUND: Hyponatremia is associated with pneumonia, and aspiration pneumonia is common in the elderly, however, there has been no study of hyponatremia in this population. OBJECTIVE: To determine the impact of hyponatremia on mortality in elderly patients with aspiration pneumonia, while focusing on the comparison between those with and without the syndrome of inappropriate antidiuresis (SIAD). DESIGN: Retrospective review of existing database and medical records. SETTING: A community teaching hospital in Japan. PATIENTS: Two hundred and twenty-one elderly patients hospitalized with aspiration pneumonia. MEASUREMENTS: Multivariate logistical regression models were used to compare 30-day and in-hospital mortality, in patients with hyponatremia of various severities and etiologies, with that in patients with normal serum sodium concentrations. RESULTS: Sixty-five (29%) of 221 patients had hyponatremia. Of these 62 (95%) had hypotonic hyponatremia, which were further assessed as having hypovolemic (39 [63%]), hypervolemic (3 [5%]), and euvolemic (20 [32%]) hyponatremia. Of the 20 euvolemic patients, 14 (70%) had SIAD. Both moderate and severe hypotonic hyponatremia were significantly associated with increased in-hospital mortality (odds ratio [OR] 6.05, 95% confidence interval [CI] 1.46-25.0, and OR 5.65, 95% CI 1.14-28.1, respectively). Hyponatremia due to SIAD was significantly associated with both increased 30-day mortality (OR 7.40, 95% CI 1.73-31.7) and increased in-hospital mortality (OR 22.3, 95% CI 4.26-117). In contrast, hypovolemic hyponatremia was not significantly associated with increased mortality. CONCLUSIONS: Hyponatremia due to SIAD was strongly associated with increased mortality in elderly patients with aspiration pneumonia, whereas hypovolemic hyponatremia was not associated with increased mortality.