Free Water Calculator
Definitions
- Free Water (FW): The amount of water that is not bound in a substance and can be removed through processes like drying or heating.
- Body Weight (BW): The weight of a person in kilograms.
- Extra Water Needed (E): The additional water required due to exercise or hot weather, measured in minutes of exercise or degrees above 20°C.
Example
Let's say the body weight (BW) is 70 kg and the extra water needed (E) is 30 minutes of exercise. Using the formula:
\[
FW = (70 \times 0.033) + (30 \times 0.001)
\]
We get:
\[
FW = 2.31 + 0.03 = 2.34 \text{ liters}
\]
So, the amount of free water needed per day is approximately 2.34 liters.
Extended information about "Free-Water-Calculator"
Free Water Requirement Calculator
Definition: A tool to calculate the free water requirements for patients, especially those on tube feeds.
Formula: \( \text{Free Water} = \text{Total Water Requirement} - \text{Water from Tube Feeds} \)
- Free Water: Amount of additional water needed (mL)
- Total Water Requirement: Total daily water requirement (mL)
- Water from Tube Feeds: Water provided by tube feeds (mL)
Example: \( \text{Free Water} = 2000 - 1500 \)
- Free Water: Amount of additional water needed
- Total Water Requirement: 2000 mL
- Water from Tube Feeds: 1500 mL
Free Water Calculator for Hyponatremia
Definition: A tool to calculate the free water deficit in patients with hyponatremia.
Formula: \( \text{Free Water Deficit} = \text{TBW} \times \left( \frac{\text{Na}_{desired} - \text{Na}_{current}}{\text{Na}_{desired}} \right) \)
- Free Water Deficit: Amount of water deficit (L)
- TBW: Total body water (L)
- \( \text{Na}_{desired} \): Desired sodium concentration (mmol/L)
- \( \text{Na}_{current} \): Current sodium concentration (mmol/L)
Example: \( \text{Free Water Deficit} = 42 \times \left( \frac{140 - 125}{140} \right) \)
- Free Water Deficit: Amount of water deficit
- TBW: 42 L
- \( \text{Na}_{desired} \): 140 mmol/L
- \( \text{Na}_{current} \): 125 mmol/L
Free Water Replacement Calculator
Definition: A tool to calculate the amount of free water needed to replace deficits in patients.
Formula: \( \text{Free Water Replacement} = \text{Free Water Deficit} + \text{Ongoing Losses} \)
- Free Water Replacement: Total amount of water needed (mL)
- Free Water Deficit: Initial water deficit (mL)
- Ongoing Losses: Additional water losses (mL)
Example: \( \text{Free Water Replacement} = 1000 + 500 \)
- Free Water Replacement: Total amount of water needed
- Free Water Deficit: 1000 mL
- Ongoing Losses: 500 mL
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