Burn Wounds and The Rule of 9

Burn injuries are common at home, work and outdoors, where many heat sources are used. Before initiating treatment, a burn must first be classified, as its classification determines how it is treated.

Burns are classified in three ways:

• by depth

• by area

• location on the body

In superficial burns, the skin can become red and painful. Mild sunburns are a type of superficial burn. Partial-thickness burns are generally excruciating as the burn depth is at the level of the nerve endings. They blister and can have skin discolouration. Full-thickness burns are deep and are classically painless. They burn through the dermis.

Treatment of Superficial Burns

Treat superficial burns with aloe vera gel and for comfort, cool the area with damp, wet cloths. Aloe vera has no antimicrobial properties, however. Leaving the wound to dry increases scar formation and slows wound healing, so keep the burn moist. It is essential to avoid further exposure to heat and sunlight. Patients with these types of burns might be able to stay in the backcountry if the pain is controlled.

Treatment of Partial and Full Thickness Burns

Partial and full-thickness burns are more serious and will be painful. Gently clean the burn with cool water to remove loose skin and debris and trim away all loose skin. Apply a thin layer of antibacterial Ointment (i.e. Silvadene) to the burn and cover it with a non-adhesive, sterile dressing. Inspect the wound and change the dressing at least once a day. These might be too painful to keep in the backcountry. Do not apply ice directly to burns for more than 15 minutes, as this may cause more tissue damage due to a decreased blood supply to the area.

The Rule of 9’s

The size of a burn can be quickly estimated by using the "rule of nines." This method divides the body's surface area into percentages.

• The front and back of the head and neck equal 9% of the body's surface area.

• The front and back of each arm and hand equal 9% of the body's surface area.

• The chest equals 9% and the stomach equals 9% of the body's surface area.

• The upper back equals 9% and the lower back equals 9% of the body's surface area.

• The front and back of each leg and foot equal 18% of the body's surface area.

• The genital area equals 1% of the body's surface area.

If a person is injured due to a burn, a doctor may assess them quickly using the rule of 9s. For example, if they were burned on each hand and arm as well as the front trunk portion of the body, using the rule of nines, they’d estimate the burned area as 36% of a person’s body. The rule of nines can also relay to a medical team receiving the patient how serious the injury is. Providers also know that burns that exceed 30% of a person’s body can be potentially fatal.

Healthcare providers don’t typically use the same calculations in the rule of nines for children. This is because children tend to have different body proportions than adults do, including larger heads and smaller legs. For example, children tend to proportionally have a 20% larger head than adults. Infants also have 13% smaller legs than adults.

Therefore, there are a few adjustments to the rule of nines in children:

• Head and neck18%

• Arm (including the hand) 9% each

• Legs (including the feet) 14% each

• Front of the body (trunk) 18%

• Back of the body (trunk) 18%

Another quick method to work out a patient’s burns percentage, especially if it is smaller areas all over the body, is to use the size of the patient’s hand as 1% surface area.

Burns are serious, painful injuries that require immediate treatment and intervention. The rule of nines serves as a quick method of assessment for a medical provider to estimate the extent of a person’s injuries. If the person with burns is a child, the rule of nines should be adjusted due to differences in a child’s proportions.