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

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.