💧 Adrogué–Madias Fluid Formula
The Adrogué–Madias formula predicts how each liter of a chosen infusate will change serum sodium, guiding dysnatremia correction.
Adrogué–Madias Fluid Formula
Current serum sodium (mmol/L)
Weight (kg)
Sex
Elderly
Infusate type
When to use
Enter current sodium, weight, sex, age category, and infusate; the tool returns the predicted ΔNa per liter and estimated total body water.
How it works
ΔNa per liter = (infusate Na − serum Na) / (total body water + 1). TBW = weight × factor (0.6 male, 0.5 female; 0.5/0.45 if elderly).
Key points
- Limit chronic hyponatremia correction to ≤8–10 mmol/L/24h to avoid osmotic demyelination, and chronic hypernatremia to ≤10–12 mmol/L/24h to avoid cerebral edema (original synthesis · not guideline verbatim).
- The formula ignores ongoing urinary and insensible losses, so it is a starting estimate that requires frequent re-measurement.
- Hypertonic 3% saline (Na 513) raises sodium fastest; 5% dextrose (Na 0) lowers it and is used for hypernatremia.
References
- Adrogué HJ, Madias NE. Hyponatremia. N Engl J Med. 2000.
- Adrogué HJ, Madias NE. Hypernatremia. N Engl J Med. 2000.
Decision support for licensed clinicians only; not a substitute for clinical judgement, diagnosis or local protocols.