Initial Evaluation of Burns
There have been many advances in burn wound management that have decreased morbidity and mortality from burns. One of the best advancement has been to excise the burn wound as soon as possible, closing the wound after excision or allowing for secondary healing of the healthy tissue.
Previous to these advancements, burns were allowed to heal over several weeks with removal of dead tissue only. There were higher rates of infection and skin grafts weren’t done until about 3-8 weeks following the burn.
Only about half of all skin grafts were successful so that repeated grafting was necessary. Scarring was worse and there were more joint contractures.
Now, burns that aren’t expected to heal completely within three weeks are excised and the healthy tissue is allowed to heal. The trick is in evaluating the wound so that you can tell the difference between a quickly healing burn and a burn that will take longer to heal.
The Biology of Skin
Skin is considered a single organ and is the largest organ of the body. It consists of two layers: the epidermis and the dermis. The epidermis can be as thin as 0.05 millimeters or as thick as 1 millimeter, depending on the body area it occurs on. It consists mainly of keratinocytes which give the water protection and toughness to the skin. There are several sub-layers to the epidermis that begin deep and gradually migrate out to the outside in order to be sloughed off. Eventually, the cells on the topmost part of the skin have no nuclei and are, in effect, dead cells.
Melanin is in the epidermis, too. This is contained in melanocytes that protect the tissue from the effects of the sun and other sources of UV radiation. There are also cells called Langerhans cells, which help in skin immunity to pathogenic bacteria, yeast and viruses.
If a burn is isolated to the epidermis only, the body is capable of regenerating that tissue so that there is very little scarring and a low risk of infection. The melanocytes don’t regenerate as easily, however, so there can be pigment changes within the burned area. These effects are generally permanent.
The epidermis is connected to the deeper dermis of the skin by the basement membrane. The basement membrane has projections that knit the two skin layers together. These projections may take longer to heal than the epidermis alone so that the epidermis will not be tightly connected to the dermis for several weeks.
The dermis of the skin has a lot of collagen fibers to fill out the tissue. These fibers also allow for the stretchiness of the skin. Elastin fibers are present as well which give skin its elastic recoil. Both of these fibers are made by fibroblasts, which are the main cells of the dermis. Things like sweat glands and hair follicles originate in the dermis portion of the skin and push out through the epidermis to the outside. The dermis does not regenerate like the epidermis; instead it heals by making scar tissue.
During a Burn…
During a burn, the center of the injury is the most dead, with more vital tissue spreading out to the outside of the wound. The middle of the burn is called the “zone of coagulation”, where all the cells are dead. Around that is the “zone of stasis”, which has mixed dead and living cells. The circulation is poor in that area. If not well treated, this area will die, too. The outside area is called the “zone of hyperemia”, which generally heals on its own. The circulation is good here.
A burn diameter can be reduced through proper care, such as giving extra fluids so the zone of stasis doesn’t dry out. Topical antimicrobial ointments help prevent infection in this area. Cooling of the burn is important to decrease its diameter; however, it must be done shortly after the burn is sustained. It doesn’t really work that well otherwise. The water temperature during cooling can’t be too cold or the circulation around and inside the burn will worsen and more cells will die. If the burn is
minor, it should be cooled for about 30 minutes but no longer.
Assessing a Burn
A burn can go through just the epidermis or through the dermis as well. It can even go deeper into subcutaneous fat, muscle and bone. Epidermal burns tend to hurt a great deal but do not blister. Superficial dermal burns are
also painful but tend to blister. Deep to the blister is pink and red tissue that is very sensitive to touch.
Deep dermal burns take more than three weeks of healing time. Blistering occurs as in superficial dermal burns but the underlying skin is more mottled and has white and pink areas. Deep dermal burns are less painful than
superficial dermal burns. If they are not predicted to heal within three weeks, the burned tissue should be cut away from the healthier tissue underneath and skin grafted.
Full thickness burns can look charred, brown and leathery. They do not hurt to touch or even to a pin prick. If the burn is not charred, it can look white and will not blanch when pressure is applied to the affected area. The lack
of blanching is what differentiates it from superficial burns as the circulation in these burns is very poor.
Common Types of Burns
The types of burns that can occur include the following:
- Flash burns. These are caused by an accelerant like gasoline or kerosene. They have a quick duration of action with the worst part of the burn being the closest to the origin of the accelerant. They may cover large areas but require fewer skin grafts than other types of burns.
- Flame burns. These are from fires and are almost always full thickness or deep dermal burns. If clothing or bedding is involved, the burns tend to be deeper and involve the full thickness of the skin or worse.
- Scald burns. These come from hot water contact such as with a hot bath or scalding coffee. If the water is boiling, it tends to cause a deep dermal burn. Deeper burns happen if the liquid is viscous, such as with a soup or gravy. Clothed skin keeps the hot liquid in contact with the skin longer, so the burn tends to be deeper. Grease or hot oil burns can easily cause full thickness burns. Thirty to forty percent of these types of burns require skin grafting. Tar burns also cause full thickness burns that are difficult to treat because the tar sticks to the underlying burn. Tar can be removed by applying petrolatum jelly and a dressing that is changed every two to four hours until the tar is gone.
- Contact burns. These are caused by directly coming in contact with a hot surface such as metal, coal, glass or plastic. These injuries tend to be smaller but very deep. These usually require some kind of skin grafting in order to heal.
- Chemical burns. These are usually caused by strong alkali or acid burns. The burns are progressive until the entire chemical is neutralized by the burning tissue. Acid burns are less severe because they tan the skin and create a barrier that prevents the acid from going deeply into the tissue. Alkali burns are serious because they tend to “melt away” tissue until neutralized. Chemical burns should be considered full thickness or at least deep dermal until proven otherwise.
- Electrical burns. These are really the same thing as thermal burns coming from high intensity heat sources. The higher the voltage from the electrical burn, the deeper is the burn in general.