RESUMEN
BACKGROUND: Hyponatremia (HNA) is a common electrolyte disturbance associated with morbidity and mortality. The aim of this study was to assess incidence and prognosis value of HNA in the Emergency Department (ED). METHODS: A retrospective observational case-control study has been conducted in the ED during 10 months. Control patients (Na 135-145 mmol/L) were matched, in a 1:1 ratio, on age, gender and month of ED admission with hyponatremic patients (Na<130 mmol/L). RESULTS: Two hundred fifty-six patients (2.4% of patients with a blood analysis) had HNA among which 166 were matched with 166 normonatremic controls. HNA patients had more often a history of asthma/chronic obstructive pulmonary disease (P=0.002) and solid tumors (P=0.001), received more diuretics (P=0.026), and presented more often with vomiting (P=0.034). Admission to the hospital or to the ICU was more frequent in HNA patients (89% vs. 52%, P<0.001; 13% vs. 3%, P=0.003, respectively). Patients with HNA presented more frequently at least one complication (digestive, septic, respiratory, renal, and cardiovascular) during their hospital/ICU stay (40% vs. 4%, P<0.001). Mortality rate was higher in HNA than in controls (10% vs. 3%, P=0.021). The multivariable conditional logistic regression analysis showed an independent association of HNA with solid tumors (OR=4.12; 95% CI: 1.68 to 10.1) and hospital death (OR=2.90; 95% CI: 1.03 to 8.17). CONCLUSION: HNA was present in 2.4% of patients with a blood analysis and was associated independently with solid tumors and hospital death.