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Quick GuideFirst Aid: Properly Caring for Wounds
What is the significance of the amount of body area burned?
In addition to the depth of the burn, the total area of the burn is significant. Burns are measured as a percentage of total body area affected. The "rule of nines" is often used, though this measurement is adjusted for infants and children. This calculation is based upon the fact that the surface area of the following parts of an adult body each correspond to approximately 9% of total (and the total body area of 100% is achieved):
- Head = 9%
- Chest (front) = 9%
- Abdomen (front) = 9%
- Upper/mid/low back and buttocks = 18%
- Each arm = 9%
- Each palm = 1%
- Groin = 1%
- Each leg = 18% total (front = 9%, back = 9%)
As an example, if both legs (18% x 2 = 36%), the groin (1%) and the front chest and abdomen were burned, this would involve 55% of the body.
Only second and third degree burn areas are added together to measure total body burn area. While first degree burns are painful, the skin integrity is intact and it is able to do its job with fluid and temperature maintenance.
If more than15%-20% of the body is involved in a burn, significant fluid may be lost. Shock may occur if inadequate fluid is not provided intravenously. As the percentage of burn surface area increases, the risk of death increases as well. Patients with burns involving less than 20% of their body should do well, but those with burns involving greater than 50% have a significant mortality risk, depending upon a variety of factors, including underlying medical conditions and age.