Sodium levels on admission are associated with mortality risk in hospitalized patients

Aims: Abnormal sodium values are common among hospitalized patients. We aimed to investigate the association of admission sodium values and mortality. Methods: Historical prospectively data of adult patients hospitalized to medical wards between January 2011 and December 2013. Admission sodium values were classified to five categories: severe hyponatremia (<125 mEq/L), mild hyponatremia (125-135 mEq/L), normal sodium values (135-145 mEq/L), mild hypernatremia (145-150 mEq/L) and severe hypernatremia (>150 mEq/L). Main outcomes were length of hospitalization, in-hospital mortality and mortality at the end-of-follow-up. Results: The cohort included 27,889 patients (mean age 67 +/- 18 years, 52% males). The total follow-up was 1065 days. Most patients had normal sodium values (76%), 22% had hyponatremia, 3% had hypernatremia. Mean age increased with increase in severity of hyponatremia or hypernatremia. Median length of hospitalization was longer with mild and severe hypernatremia (7 and 5 days, respectively) or with mild and severe hyponatremia (4 and 4 days, respectively), compared to normal sodium levels (3 days). Compared to in-hospital mortality with normal sodium levels (5%), mortality was higher with mild and severe hyponatremia (9% and 14%, respectively) and was highest with mild (28%), and severe hypernatremia (52%). Mortality rate at the end of follow-up was 28% with normal sodium levels, 44% and 48% with mild and severe hyponatremia, 66% and 90% with mild and severe hypernatremia, respectively. Conclusions: Abnormal sodium values on admission were associated with longer hospitalization and increased short- and long-term mortality. Mortality risk was higher with hypernatremia, compared to hyponatremia. (C) 2017 European Federation of Internal Medicine. Published by Elsevier B.V. All rights reserved.