Expected Na change per litre of infusate (Adrogue-Madias)

ΔNa = (infusate Na + K − serum Na) ÷ (TBW + 1). Estimate only; recheck Na every 2-4 h.

Serum sodium

mmol/L

Infusate Na + K

mmol/L

Weight

Patient group

Expected change per 1 L

12.8 mmol/L

Formula

(infNa - serumNa) / (weight * tbwFactor + 1)

Notes

3% saline = 513 mmol/L Na; 0.9% saline = 154; Ringer's lactate ≈ 130 (+4 K); D5W = 0. Limit correction to ≤ 10 mmol/L in 24 h (≤ 8 if high risk of osmotic demyelination).

References

Adrogue HJ, Madias NE. Hyponatremia. N Engl J Med 2000;342:1581-9.
Spasovski G, et al. Clinical practice guideline on diagnosis and treatment of hyponatraemia. Eur J Endocrinol 2014;170:G1-47.

Used in

Hyponatraemia Hypernatraemia

Calculators support, not replace, clinical judgement. Check inputs and units, and confirm doses with your unit protocol.