Abstract

Background: Patients who develop hyponatremia during their hospitalization have higher hospital mortality. Aim: To determine if the presence of hyponatremia on admission to the emergency room is a risk factor for hospital mortality. Patients and Methods: Two hundred forty five patients consecutively admitted to the emergency room and then transferred to the Medicine Department, where they finally died, were matched for age and gender with 245 control subjects admitted to the emergency room and hospitalized in the Medicine Department at the same time, but survived. The dependent variable was death, and the exposure variable was hyponatremia. Admission diagnosis and Charlson comorbidity index was considered as confounding variables. Results: Hyponatremia at admission occurred in 30 and 17% of patients who died and survived, respectively, rendering an adjusted odds ratio for death of 2.13(95% confidence intervals = 1.27-3.57). Charlson Comorbidity Index according to age score was higher in subjects with hyponatremia compared to those without hyponatremia (8.1 +/- 3.1 and 7.2 +/- 2.8; p = 0.01). Multivariate analysis showed that age, gender, length of stay, cause of hospitalization and chronic diseases did not significantly modify the effect of hyponatremia on hospital mortality. Conclusions: Hyponatremia on admission at emergency room had a significant association with hospital mortality. Subjects with hyponatremia had a higher Charlson Comorbidity Index score. (Rev Med Chile 2011; 139: 985-991).