1. What is Total Body Water Deficit?

Total Body Water Deficit is a calculation used to estimate the amount of free water needed to correct hypernatremia (elevated serum sodium levels). It helps clinicians determine appropriate fluid replacement therapy.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( TBW \) — Total Body Water (L)
• \( Na \) — Current Serum Sodium (mmol/L)
• 140 — Normal Serum Sodium (mmol/L)

Explanation: The formula calculates the water deficit needed to restore serum sodium to the normal value of 140 mmol/L.

3. Importance of Calculating Water Deficit

Details: Accurate calculation of water deficit is crucial for proper management of hypernatremia, guiding fluid replacement therapy, and preventing complications from over- or under-correction.

4. Using the Calculator

Tips: Enter total body water in liters and current serum sodium level in mmol/L. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: How is total body water (TBW) estimated?
A: TBW is typically estimated as 60% of body weight in kilograms for men and 50% for women, though this can vary based on age and body composition.

Q2: What is a normal serum sodium level?
A: Normal serum sodium typically ranges from 135-145 mmol/L, with 140 mmol/L often used as the target for correction calculations.

Q3: How quickly should water deficit be corrected?
A: Correction should generally be gradual, typically not exceeding 0.5 mmol/L per hour to avoid complications like cerebral edema.

Q4: Are there limitations to this calculation?
A: This formula provides an estimate and doesn't account for ongoing losses. Clinical judgment and monitoring are essential during correction.

Q5: When is this calculation most useful?
A: This calculation is particularly valuable in managing hypernatremic dehydration and guiding fluid therapy in hospitalized patients.