Abstract
The aim of this study was to analyze the impact and the clinical and evolutionary characteristics of hypotonic hyponatremia in patients hospitalized in Internal Medicine units. Prospective multicenter observational study of patients with hypotonic hyponatremia (<135 mmol/L) in 5 hospitals in southern Spain. Patients were included according to point prevalence studies carried out every 2 weeks between March 2015 and October 2017, by assessing demographic, clinical, analytical, and management data; each patient was subsequently followed up for 12 months, during which time mortality and readmissions were assessed. A total of 501 patients were included (51.9% women, mean age = 71.3 ± 14.24 years), resulting in an overall prevalence of hyponatremia of 8.3%. The mean comorbidities rate was 4.50 ± 2.41, the most frequent diagnoses being heart failure (115) (23%), respiratory infections (65) (13%), and oncological pathologies (42) (6.4%). Of the total number of hyponatremia cases, 180 (35.9%) were hypervolemic, 164 (32.7%) hypovolemic, and 157 (31.3%) were euvolemic. A total of 87.4% did not receive additional diagnostic tests to establish the origin of the condition and 30% did not receive any treatment. Hospital mortality was 15.6% and the mean length of stay was 14.7 days. Euvolemic and admission hyponatremia versus hyponatremia developed during admission were significantly associated with lower mortality rates (P = .037). Mortality at 1 year and readmissions were high (31% and 53% of patients, respectively). Hyponatremia was common in Internal Medicine areas, with hypervolemic hyponatremia being the most frequent type. The mortality rate was high during admission and at follow-up; yet there is a margin for improvement in the clinical management of this condition.