Burns

The skin is the largest organ in the body, serving as a barrier to infection, a surface for sensation, and as a means of thermal regulation and fluid balance. The skin has several layers, but is typically divided into 3 for the purpose of discussion:

1. The Epidermis

2. The Dermis

3. The subcutaneous tissue

Burns are classified by the degree of damage they cause to these 3 layers of tissue.

• First degree/Superficial: Burns of this degree affect only the epidermis, and typically present with redness and warmth, but there is no break in the continuity of the skin.

• Second degree/partial thickness: These burns affect the epidermis and varying degrees of the dermis. They usually present with significant pain, redness, and blistering of the skin.

• Third degree burns/full thickness: These affect al layer of the skin and may involve the bone. They present with severe pain at the margins, and absence of sensation in the central areas. Skin is charred.

Damage to the skin by a burn presents several problems:

• There is a portal of entry for pathogens

• Massive fluid shift is possible

• Thermoregulation is impaired

There are several types of burns, classified by mechanisms:

Thermal burns:

• Flame burns: As the name implies, these burns are caused by open flames. They are typically significant due to direct exposure to the heat source, risk of clothing catching fire, and the potential for airway involvement.

• Scald burns: These are caused by immersion in hot liquids, or exposure to steam or superheated gases.

• Contact burns: These are burns that occur when part of the body is placed against a hot surface such as a stove.

• Flash burns: Essentially the same as flame burns, but are caused by things such as exposure to the light from a welding torch. They often involve unprotected eyes.

A major concern with thermal burns, particularly those involving smoke, is the risk of airway burns. While it is rare for the lower airway to be affected, the structures of the upper airway tend to absorb the majority of the heat, and it is here we see the most damage. Burns to the upper airway present a significant airway risk, due to fluid shift and inflammation. These patient's require close monitoring, and may progress to potentially requiring intubation. Smoke inhalation also carries a significant risk of carbon monoxide and cyanide poisoning, and this needs to be considered.

Chemical burns:

There are several ways in which chemicals can cause tissue burns:

• Dessication: These chemicals pull water from the surrounding tissues, leading to cellular dehydration and necrosis.

• Vessicants: These chemicals produce blistering on the surface of the skin.

• Oxidants: These chemicals insert oxygen, sulfer, or halogen into the proteins in the tissues.

• Corrosives: Cause denaturing of proteins in the skin.

• Reductions: Damages the amine linkages between proteins

• Protoplasmics: Form esters with proteins.

There are various acids and bases that can cause significant burns as well. When in doubt, attempt to consult the MSDS or Hazmat for direction.

Burn Shock:

When tissue is burned, capillaries leak fluid into the intravascular space, and into the interstitial space. This fluid is hypotonic, and so it shifts into the cells, causing cellular swelling. There are also changes in circulating electrolytes, and proteins, as cells in the burned area lyse. This leads to massive fluid shifting out of the vascular space, renal damage, and potential cardiac arrhythmias. Fluid resuscitation is essential in maintaining MAP, and preventing severe hypovolemia from taking place. Burn shock typically sets in over 6-8 hours. In the prehospital field we can address this concern with isotonic fluid administration. Typically we can calculate fluid needs using the Parkland Burn Formula.

4cc x TBSA burned x Bodyweight in Kg

We give divide the result in half and give the first half over 8 hours and the following half over 16 hours.