Nephrology

Sodium Deficit in Hyponatremia

Calculates total body sodium deficit for correction.

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Parameters

Sodium Deficit in Hyponatremia Result

Formula

Sodium Deficit (mEq) = TBW × (Target Na - Measured Na)

TBW Factors:
Male < 65 yrs: 0.6
Male ≥ 65 yrs: 0.5
Female < 65 yrs: 0.5
Female ≥ 65 yrs: 0.45

Clinical Pearls

Guides the volume of hypertonic saline or normal saline needed to safely correct severe symptomatic hyponatremia.

Limitations

Calculations are estimates. Frequent serum sodium monitoring (every 2-4 hours) is mandatory during correction. The Adrogué-Madias formula is often preferred for calculating the expected change in serum Na per liter of infusate.