The Evans formula, developed in 1952, is the first burn formula designed to calculate fluid resuscitation needs based on a patient's body weight and burn surface area (BSA). It's crucial for treating severe burns to prevent complications from dehydration and shock.
Understanding the Calculation
The formula dictates fluid administration over the first 24 hours post-burn. It's composed of three parts:
- Crystalloids: 1 ml/kg/% BSA
- Colloids: 1 ml/kg/% BSA
- Glucose in water: 2000 ml
This means for each kilogram of body weight and each percentage point of total body surface area burned, 1 ml of crystalloid and 1 ml of colloid solution are administered. An additional 2000 ml of glucose in water is added to this total.
Example:
A 70 kg patient with a 20% BSA burn would require:
- Crystalloids: (70 kg 20%) 1 ml/kg/% = 1400 ml
- Colloids: (70 kg 20%) 1 ml/kg/% = 1400 ml
- Glucose in water: 2000 ml
- Total: 4800 ml over the first 24 hours
Important Considerations
- The Evans formula provides a starting point for fluid resuscitation. Individual patient needs may vary.
- Close monitoring of fluid balance and vital signs is crucial.
- This formula is primarily for the initial 24 hours. Fluid requirements are reassessed frequently afterwards.
- Other burn formulas exist, such as the Parkland formula, offering alternative approaches to fluid management.
Note: This information pertains specifically to the burn formula attributed to Evans. Several other formulas and individuals share the name "Evans," as evidenced in the provided links (e.g., Evans index in radiology, Mitch Evans in Formula E).
