NaCl 3% Bolus Therapy as Emergency Treatment for Severe Hyponatremia: Comparison of 100 mL vs 250 mL

Context The aim of initial treatment of severe hyponatremia is to rapidly increase serum sodium to reduce the complications of cerebral edema. The optimal strategy to achieve this goal safely is still under debate. Objective To compare the efficacy and safety of 100 and 250 mL NaCl 3% rapid bolus therapy as initial treatment of severe hypotonic hyponatremia. Methods Retrospective analysis of patients admitted to a teaching hospital in The Netherlands between 2017 and 2019. The patients were 130 adults with severe hypotonic hyponatremia, defined as serum sodium <= 120 mmol/L. A bolus of either 100 mL (n = 63) or 250 mL (n = 67) NaCl 3% was the initial treatment. Successful treatment was defined as a rise in serum sodium >= 5 mmol/L within the first 4 hours after bolus therapy. Overcorrection of serum sodium was defined as an increase of more than 10 mmol/L in the first 24 hours. Results The percentage of patients with a rise in serum sodium >= 5 mmol/L within 4 hours was 32% and 52% after a bolus of 100 and 250 mL, respectively (P = .018). Overcorrection of serum sodium was observed after a median of 13 hours (range 9-17 hours) in 21% of patients in both treatment groups (P = .971). Osmotic demyelination syndrome did not occur. Conclusion Initial treatment of severe hypotonic hyponatremia is more effective with a NaCl 3% bolus of 250 mL than of 100 mL and does not increase the risk of overcorrection.