The Evans formula, developed in 1952, is one of the earliest formulas used to calculate fluid resuscitation in burn patients. It considers both the patient's weight and the percentage of total body surface area (TBSA) affected by the burn. The formula emphasizes fluid replacement during the crucial first 24 hours post-burn.
The Formula
For the first 24 hours, the Evans formula recommends administering the following fluids:
- Crystalloids: 1 ml/kg/%TBSA
- Colloids: 1 ml/kg/%TBSA
- Dextrose (Glucose) in Water: 2000 ml
Example: A 70kg adult with 20% TBSA burns would receive:
- Crystalloids: 1 ml/kg 70 kg 20% = 1400 ml
- Colloids: 1 ml/kg 70 kg 20% = 1400 ml
- Dextrose in Water: 2000 ml
Total: 4800 ml of fluids in the first 24 hours.
Variations and Considerations
While the original Evans formula is cited as using 1 ml/kg/%TBSA for both crystalloids and colloids, some sources mention variations, like the one in a Pediatric Burn Resuscitation article mentioning 2 ml/kg/%TBSA for total fluid requirement in addition to maintenance fluids. https://pmc.ncbi.nlm.nih.gov/articles/PMC5582395/ It's crucial to note that the Evans formula is one of several methods available, and its application should be tailored to the individual patient’s condition and the specific clinical setting under the guidance of medical professionals. Other formulas, such as the Parkland formula, are also commonly used and may be preferred depending on the circumstances.
The Evans formula represents a historical milestone in burn resuscitation, being among the first to incorporate both weight and burn surface area. https://www.facs.org/media/imrpwzel/06_everett_evans.pdf However, modern burn management often employs more refined approaches to fluid resuscitation.
