The Cardiovascular
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Sodium Deficit in Hyponatremia

Total sodium needed to reach a target serum concentration.

Sodium Deficit in Hyponatremia
Body weight
Total body water fraction
Current serum sodium
mEq/L
Target serum sodium
mEq/L
Complete the fields above to see the result.

When to use

  • Estimating the total amount of sodium to replace when correcting hyponatremia.

Formula

Sodium deficit (mEq) = total body water x (target Na - serum Na); total body water = weight x fraction.

Pearls and pitfalls

  • This gives total sodium to replace, not the rate; cap the daily rise to avoid osmotic demyelination.

References

  1. Adrogue HJ, Madias NE. N Engl J Med. 2000;342(21):1581-9.