Treatment of moderate-severe hyponatremia in an emergency department: a retrospective study

BACKGROUND: Hyponatremia is observed in 3-10% of emergency departments (ED) patients. Its early correction in ED is advisable since persisting low levels of sodium (Na+<120 mEq/L) are associated with in-hospital mortality. Too rapid correction, conversely, may lead to osmotic demyelination syndrome (ODS).METHODS: Clinical records of 201 patients who remained in the San Paolo Hospital ED, Milan, for 24-48 hours with moderate-severe hyponatremia (Na+≤130 mEq/L), were reviewed. Symptoms, comorbidities, previous therapies, body fluid status, were considered as well as the effect of therapy on sodium plasma concentration and patient outcome.RESULTS: The sodium plasma levels increased from 124±4 to 129±3 after 24 h and 132±4 mEq/L after 48 h. (ANOVA P<0.0001); 65% of patients had sodium plasma levels ≥130 mEq/L after 48 h. Severe hyponatremia was corrected at a faster rate. Mean sodium chloride infusion tonicity varied from 1.1% to 1.3%, in groups of patients with different hyponatremia severity (ANOVA P<0.0001). Less water was infused in hypervolemic than in normo- and hypovolemic patients (ANOVA P<0.005). In 10% of patients Na+ increased more than the limit considered safe to avoid ODS (8 mEq/L). Adrogué and Manias formula predicting the change in serum sodium based on given infusion rate, underestimates the observed sodium increase, particularly when infusions of greater tonicity were used.CONCLUSIONS: Hyponatremia treatment in ED was overall cautious, modulated on patient sodium levels and body fluid status at admission. The main determinant of sodium “over-correction” was renal and extrarenal fluid losses ongoing during sodium infusion.