Burn severity grading

When we assess the severity of a burn, we mainly look at the size of the affected surface area and how deep the tissue damage is. Obviously, many other factors need consideration, like which anatomical location is involved, what caused the burn, the patient's age and general health status, and many other denominators. These factors help us determine at what level of care the patient should be treated, how much fluid substitution the patient needs, and the prognosis for the outcome.

Minimal Criteria for Transfer to a Burn Centre

 

Burn injury patients who should be referred to a burn unit include the following:

 

(i) all burn patients less than 1 year of age

(ii) all burn patients from 1 to 2 years of age with burns >5% total body surface area (TBSA)

(iii) patients in any age group with third-degree burns of any size

(iv) patients older than 2 years with partial-thickness burns greater than 10% TBSA

(v) patients with burns on particular areas—face, hands, feet, genitalia, perineum or major joints

(vi) patients with electrical burns, including lightning burns

(vii) chemical burn patients

(viii) patients with inhalation injury resulting from fire or scald burns

(ix) patients with circumferential burns of the limbs or chest

(x) burn injury patients with preexisting medical disorders that could complicate management, prolong recovery, or affect mortality

(xi) any patient with burns and concomitant trauma

(xii) paediatric burn cases where child abuse is suspected

(xiii) burn patients with treatment requirements exceeding the capabilities of the referring centre

(xiv) septic burn wound cases.

The rule of nines
 

The rule of nines was developed to be able to quickly assess the surface area which is damaged by a burn. This tool divides the body's surface areas into percentages. Note that we only consider 2nd and 3rd degree burns when using the rule of nines. Children are not small adults, and they have different body proportions. Most importantly, the head's surface area in small children is significantly larger than in adults. In infants, for example, the surface area of the entire head is about 18%, while that of an adult is about 9%. We, therefore, use different charts for adults and children. Remember to examine the entire body when assessing a burn patient. It can quickly happen that you oversee a severe burn somewhere else on the body if you do not unclothe the patient. However, especially in small children, it is essential to avoid hypothermia - make sure that the room is warm and cover the patient again as soon as possible. 

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Figure 1  The rule of nines fits best to the proportions in adults. In teenagers and younger children, the proportions are difficult. In general, it is not necessary to be so exact. It is impossible to remember the exact proportions for each age group. The main thing is to remember that the head of children is significantly larger in proportion than in adults. Note that some authors apply 10% surface area to the head of adults - for the rule of nines, we estimate the head to be 9%. Again, these are minor details that should not lead to confusion. 

Video 1  The rule of nines is well explained in this video by Dr. Cambell. The video is about 7 minutes long. Click on the image above to see the film. copyright: Dr. Campbell

Classification of burns according to depth

Assessing the depth of the tissue damage is essential to determine the severity of the burn correctly and to choose the right treatment. It is usually not difficult to determine the depth of the injury. However, the most common mistake is to underestimate the severity of the burn. Sometimes what seemed like a first-degree burn starts to blister the next day, which implies that this was actually a second-degree burn. In other words - sometimes, we need to observe the burn for a few days to determine the severity correctly. Another common mistake is that health care personnel oversee a third-degree injury because the patient feels pain in the burnt area. In third-degree burns, the patient often will not feel pain. However, there usually is a mix of second and third-degree injuries in an area with burnt skin. When the patient has pain in a burn, there can still be significant areas with third-degree burns. In the opposite case - if the patient does not have any pain sensation, you can be sure that there is third-degree damage. 

Traditionally the severity of burns was established according to the clinical appearance after the injury using the first- third ( fourth-) degree system. In the past years, this staging tool has come under criticism because it does not differentiate between superficial second-degree burns and deeper second-degree burns, which may require skin transplantation. In other words, in modern wound classification, we now have two types of second-degree burns - superficial and deep second-degree burns. 

1. First-degree burns (Superficial burns)

First-degree burns affect only the epidermis or outer layer of skin. The burn site is red, painful, dry, and with no blisters. Mild sunburn is an example. Long-term tissue damage is rare and usually consists of increasing or decreasing skin color. It may be difficult to spot a first-degree burn in dark skin types as the redness does not show as readily. 

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Figure 2 A first-degree burn (superficial burn) in a person with light skin. We have in vain tried to find a representative picture of a dark skin person with a first-degree burn. This is probably because first-degree burns hardly show in darker skin. 

2a. Superficial second-degree burns (Superficial partial-thickness burns) 

These burns characteristically form blisters within 24 hours between the epidermis and dermis. They are painful, red, weeping, and blanch with pressure. Burns that initially appear to be only epidermal in depth may be determined to be partial thickness 12 to 24 hours later. These burns generally heal in 7 to 21 days; scarring is unusual, although pigment changes may occur. A layer of fibrinous exudates and necrotic debris may accumulate on the surface, predisposing the burn wound to heavy bacterial colonization and delayed healing. These burns typically heal without functional impairment or hypertrophic scarring.

2a. Deep second degree burns (Deep partial-thickness burns) 

These burns extend into the deeper dermis and are characteristically different from superficial partial-thickness burns. Deep burns damage hair follicles and glandular tissue. They are painful to pressure only, almost always blister (easily unroofed), are wet or waxy dry, and have variable mottled colorization from patchy cheesy white to red. They do not blanch with pressure. If an infection is prevented and wounds are allowed to heal spontaneously without grafting, they will heal in two to nine weeks. These burns invariably cause hypertrophic scarring. If they involve a joint, joint dysfunction is expected even with aggressive physical therapy. A deep partial-thickness burn that fails to heal in two weeks is functionally and cosmetically equivalent to a full-thickness burn. Differentiation from full-thickness burns is often difficult.

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Figure 3  Appearance of different partial-thickness burns. In the image bottom right, there appear to be areas with deep partial-thickness skin damage close to the knuckles of the fingers. image: Shutterstock

3. Third-degree burns (Full-thickness burns)

These burns extend through and damage all dermis layers and often injure the underlying subcutaneous tissue. The burnt skin is hard and often dry - this type of burnt skin is called eschar. If the eschar is circumferential, it can compromise the blood circulation of a limb. If there is extensive eschar in the thorax area, this can compromise respiration. In these cases, an escharotomy - an incision of the eschar- is needed to prevent necrosis of the limbs or even death. 

Full-thickness burns are usually pain-free. However, all rules have their exceptions. As we mentioned earlier, there can be small patches of second-degree burns spread within an area of the third-degree burn. In other words- the patient may feel pain when we touch the burnt area leading us to believe that the burn is less severe than it is.   The rule here is: if the area is pain-free, then you can be very sure that it is a full-thickness burn. If there is some pain, you cannot be sure- it may be a deep, superficial burn or a full-thickness burn. 

Skin appearance in full-thickness burns can vary from waxy white to leathery gray to charred and black. The skin is dry and inelastic and does not blanch with pressure. Hairs can easily be pulled from hair follicles. Vesicles and blisters do not develop. Pale full-thickness burns may simulate normal skin except that the skin does not blanch with pressure. Features that differentiate partial-thickness from full-thickness burns may take some time to develop.

The eschar eventually separates from the underlying tissue and reveals an unhealed bed of granulation tissue. Without surgery, these wounds heal by wound contracture with epithelialization around the wound edges. Scarring is severe with contractures; complete spontaneous healing is usually not possible.

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Figure 4 Third-degree burn ( full-thickness burn) on lower right leg. In the area over the ankle and wrist of the foot, you can see areas with slight bleeding. This indicates that there are areas of more superficial (second-degree) damage here. The patient could sense pain here. On the shin of the lower leg, however, the dermis appears very pale, and this is an extensive area of a full-thickness burn. The patient had very little pain in this area. image: Anukool Manuton, Shutterstock

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Figure 5 Extensive third-degree burns ( full-thickness burns) in a patient. Most of the torso and upper limbs were without pain. This life-threatening injury requires treatment at the highest level of care possible - ideally, a burn center. Even at such a center, the mortality for such a severe burn injury is very high. The picture on the right show thick eschar - this went circumferential, and there was a need for escharatomies of all limbs and the torso.