Pediatric Burns By Bradley J. Phillips

physicians. It is essential that patients be properly triaged for care. Smaller burns should be treated as outpatients, while referral of more significant injuries to multidisciplinary burn centers is necessary to optimize patient care. In order to treat patients effectively, all health care providers should have a general understanding of burn physiology and care.

Pathophysiology

The skin is the largest organ in the human body, providing structural support, immunity, and regulation of heat and water loss.³ It is comprised of 3 layers: epidermis, dermis, and subcutaneous tissue. The epidermis is comprised of avascular sheets of keratinocytes. The basal layer of the epithelium continues to replicate as the superficial layers are constantly exfoliated. The epidermis acts as a mechanical barrier to infection by preventing invasion of bacteria. The dermis is more physiologically active and can be divided into 2 layers. The papillary dermis interdigitates with the epidermis, supplying the avascular layer with nutrients and oxygen. The reticular dermis is rich in collagen and elastin, giving skin its strength and elasticity.⁸ This strong reticular layer is embedded with hair follicles, nerves, sebaceous glands, and sweat glands.

Once a thermal injury is sustained, it can be separated into 3 zones: (1) the zone of coagulation, (2) the zone of stasis, and (3) the zone of hyperemia.

The zone of coagulation is characterized by severe injury with irreversible damage. This area of devitalized tissue is surrounded by the zone of stasis, which sustains lesser injury but demonstrates significant inflammation and impaired vasculature. The outermost zone of hyperemia exhibits vasodilation and increased blood flow. Injury to this area is reversible and typically resolves in 7 to 10 days.^8,9 The boundaries of these zones are dynamic and affected by management. The zone of coagulation may continue to expand in the setting of impaired blood supply. These wounds are at risk of deepening in the setting of hypovolemia, hypotension, catecholamine-induced vasoconstriction, and infection. The best-case scenario is for the zone of coagulation to remain stable while the zone of hyperemia ingresses, replacing the zone of stasis.⁸ Appropriate fluid resuscitation in the first 24 to 48 hours is the best means of avoiding worsening of wounds.³

Determining the extent of damage in a burn injury is based on the depth and the total body surface area involved. The actual thickness of skin will vary between different patients and different sites of the body. Therefore, wound depth is described relative to the layer of skin injured rather than as a numeric measurement. Knowing the remaining layer of uninjured skin provides insight on the wound’s ability to spontaneously heal versus the need for surgical intervention. Many tools have been developed in recent years to help assess the depth of injury, including dyes, laser Doppler, and thermography.^3,10 However, these methods are expensive and often not readily accessible in the daily care of patients. The depth of a wound remains primarily a clinical diagnosis, taking into account the physical examination and mechanism of injury. The preferred nomenclature divides the depth of burn injury into 4 classes: (1) superficial, (2) superficial partial thickness, (3) deep partial thickness, and (4) full thickness.

A superficial burn involves only the epidermis and is characterized by erythema and edema in the absence of blistering and desquamation. Superficial burns heal spontaneously in days and are commonly seen in sunburns.

Both superficial partial-thickness and deep partial-thickness burns involve the entire epidermis and a portion of the dermis.¹ These wounds are commonly seen in scald and flash burns.¹ Superficial partial-thickness injuries are contained within the papillary dermis, while deep partial-thickness injuries extend into the reticular dermis. Both wounds are characterized by pain and fluid-filled blisters. Debridement of superficial partial-thickness wounds will expose moist, pink tissue which blanches with pressure. These wounds will reepithelialize from retained epithelial islands and dermal appendages. They can be expected to heal within 7 to 28 days with minimal scarring.¹ Deep partial-thickness injuries destroy the epithelial interstices of the papillary dermis along with a greater proportion of the vasculature. The surface of these wounds will appear drier and will be slower to blanch with digital pressure on exam. If uncomplicated by infection, deep partial-thickness wounds can spontaneously heal in 3 to 8 weeks from the wound edges and remnant dermal appendages.^1,3 The protracted course of healing renders these deeper wounds prone to complications, such as hypertrophy and pigment changes.^3,11

The epidermis and dermis are completely destroyed in full-thickness injuries. These burns will not heal spontaneously due to destruction of dermal appendages. Full-thickness burns are leathery, insensate, and fail to blanch, corresponding to destruction of elastin fibers, nerve endings, and vasculature of the dermis.¹ Full-thickness burns are seen in flame, grease, and solid contact injuries. They are associated with multiple complications, such as acute renal failure, hyperkalemia, rhabdomyolysis, myoglobinuria, and compartment syndrome.⁸

The other major factor in defining the extent of damage is determining the total body surface area (TBSA) involved. Calculation of the TBSA includes all partial-thickness and full-thickness burns, with the exclusion of superficial