Critical care - Burns: Nursing

Burns are a type of injury where the skin and underlying tissues are damaged from exposure to heat, chemicals, electricity, or radiation. As the nurse, you’ll provide patient-centered care for critically-ill patients with burn injuries.

Okay, the skin is the largest organ in the body and provides important functions like temperature regulation, protection, sensory perception, and vitamin D production.

Its two main layers, the epidermis and dermis, rest upon the hypodermis, or subcutaneous tissue. Starting with the outermost layer, the epidermis is a waterproof barrier that shields underlying structures from mechanical stress and ultraviolet radiation. Next is the dermis which contains hair follicles, nerves, sensory receptors, sweat glands, and immune cells. Lastly is the hypodermis, made of fat and connective tissue that insulates the body and connects the dermis to the underlying muscle.

Now, the type and severity of burn injury complications will depend on the depth and the size of the burn.

Starting with burn depth, superficial burns, also known as first degree burns, involve only the epidermis.

Partial thickness burns, or second-degree burns, can be either superficial or deep. Superficial partial thickness burns involve the epidermis and the top layer of the dermis, while deep partial thickness burns affect most of the dermis.

Finally, full thickness burns are called third-degree burns when they extend through all layers of the skin and affect the subcutaneous tissue; and they're called fourth-degree burns when they extend to the underlying muscle, tendons, or bones.

Next, the size of the burn involves calculating the percentage of the total body surface area, or TBSA, impacted by the burn.

One method of quickly estimating the TBSA uses the rule of nines, which involves dividing the body into sections that each represent approximately 9% of the TBSA. For burns that affect less than 20% of the TBSA, the effects are typically localized. However, as the TBSA approaches 20% or greater, severe systemic effects occur.

So, local effects of a burn injury can be described in 3 zones. First, the zone of necrosis is the central zone where the most damage occurs, resulting in coagulative necrosis and irreversible cell death. Surrounding this is the zone of stasis, where damage to the microcirculation results in sluggish circulation. This zone is potentially salvageable with appropriate treatment. Lastly, the outermost area is the zone of hyperemia, characterized by vasodilation, increased blood flow, and limited cellular damage that can heal on its own.

As far as systemic effects of burn injuries go, cellular damage causes the release of inflammatory mediators, and the resulting inflammatory response causes increased capillary permeability and vasodilation. As capillary permeability increases, third spacing occurs as plasma proteins move out into the interstitial space, pulling fluid with them. This leads to an accumulation of fluid within the interstitial space and decreased intravascular volume. This, together with lost fluid through evaporation from the burned surface, further decreases circulating volume, resulting in hypotension. To make matters worse, vasodilation accentuates hypotension...

This precipitates a fall in cardiac output, which then culminates in a type of shock called burn shock. And the resulting decreased tissue perfusion can result in metabolic acidosis.

At the same time, increased sympathetic activity and release of stress hormones like catecholamines and cortisol produce a hypermetabolic state, leading to accelerated protein and fat metabolism, increased glucose levels, as well as increased oxygen demand.

Other problems that occur include hyperkalemia, as potassium is released from damaged cells, and as a consequence of metabolic acidosis; hypernatremia, as sodium-rich fluid is lost from the burn injury; impaired renal function due to hypoperfusion and the release of myoglobin from damaged muscle; and impaired thermoregulation and increased risk of infection due to the loss of the protective layers of the skin.

In addition, it’s important to keep in mind that burns are often accompanied by inhalation injuries from breathing super-heated air or noxious chemicals, like carbon monoxide and cyanide, that are produced during the burning process. Airway edema and laryngeal constriction can occur as well as alveoli damage that may lead to acute respiratory failure and acute respiratory distress syndrome.

Now, the clinical manifestations of a burn depend on the depth and extent of the burn, and the type of burn agent. Superficial burns are red, dry, and painful, usually without blisters. Superficial partial thickness burns produce a moist, painful, pinkish-red wound with clear, fluid-filled blisters, while deep partial thickness burns may look mottled with variable colors and can be moist or dry. Full thickness burns are often painless, and the skin can have a dry, leathery appearance. A layer of necrotic tissue called eschar develops, and bone, tendons, and muscle might be visible.