Sodium Correction Rate Calculator
Estimate change in serum Na⁺ using the Adrogue-Madias Formula
Adult Male (0.6 x Weight)
Adult Female (0.5 x Weight)
Elderly Male (0.5 x Weight)
Elderly Female (0.45 x Weight)
Child (0.6 x Weight)
0.9% NaCl (Normal Saline) – 154 mEq/L
3% NaCl (Hypertonic Saline) – 513 mEq/L
0.45% NaCl (Half Normal) – 77 mEq/L
Lactated Ringer's – 130 mEq/L
D5W (5% Dextrose) – 0 mEq/L
5% NaCl – 855 mEq/L
Calculation Results
Estimated Total Body Water (TBW):
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Change in Serum Na⁺ (per 1 Liter):
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Volume needed to change Na⁺ by 1 mEq/L:
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Medical Disclaimer: This tool is for educational and informational purposes only. It does not constitute medical advice. The Adrogue-Madias formula is an estimate. Clinical judgment and frequent laboratory monitoring are essential.
Understanding the Sodium Correction Rate Calculator
Management of dysnatremia (hyponatremia or hypernatremia) requires precise calculations to ensure safe correction of serum sodium levels. This calculator utilizes the widely accepted Adrogue-Madias formula to predict the change in serum sodium concentration after the administration of one liter of a selected infusate.
Clinical Safety Warning: Rapid correction of sodium levels can lead to severe neurological complications. In chronic hyponatremia, correction should generally not exceed 8-10 mEq/L in the first 24 hours to prevent Osmotic Demyelination Syndrome (ODS).
The Adrogue-Madias Formula
The formula used in this calculator helps clinicians estimate the effect of a specific intravenous fluid on a patient's serum sodium. The mathematical expression is:
Change in Serum Na⁺ = (Infusate Na⁺ – Serum Na⁺) / (Total Body Water + 1)
How to Use This Calculator
To obtain an accurate prediction, follow these steps:
- Patient Characteristics: Select the gender and age category. This determines the fraction of body weight composed of water (Total Body Water or TBW). For example, TBW is approximately 60% of weight in adult men and 50% in adult women.
- Weight: Enter the patient's current weight in kilograms (kg).
- Current Serum Sodium: Input the most recent laboratory value for serum sodium in mEq/L (or mmol/L).
- Selected Infusate: Choose the fluid you intend to administer. Common options like 0.9% Normal Saline (154 mEq/L) and 3% Hypertonic Saline (513 mEq/L) are provided.
Interpreting the Results
The calculator provides two key metrics:
- Change in Serum Na⁺ per Liter: This indicates how much the sodium level is expected to rise or fall if 1 liter of the selected fluid is infused.
- Volume for 1 mEq/L Change: This helps in writing orders, indicating exactly how many milliliters of the fluid are required to shift the sodium level by 1 unit.
Common Infusate Sodium Contents
Understanding the sodium content of common intravenous fluids is crucial for manual verification:
- 3% NaCl (Hypertonic): 513 mEq/L
- 0.9% NaCl (Normal Saline): 154 mEq/L
- Lactated Ringer's (LR): 130 mEq/L
- 0.45% NaCl (Half-Normal): 77 mEq/L
- D5W (5% Dextrose in Water): 0 mEq/L
Limitations
While the Adrogue-Madias formula is a standard tool in nephrology and critical care, it is a static model. It does not account for ongoing urinary or gastrointestinal losses, obligate water excretion, or activation of ADH (Vasopressin). Therefore, frequent monitoring of serum electrolytes (every 2-4 hours initially) is mandatory during active correction.