MECHANISMS OF INJURY

THERMAL INJURIES• SCALDS —70% of burns in children; They also often occur in elderly

people. Water at 140°F (60°C) creates a deep partial-thickness or full-thickness burn in 3 seconds. At 156°F (69°C), the same burn occurs in 1 second. Scald burns from grease or hot oil are usually deep partial-thickness or full-thickness burns, as the oil or grease may be in the range of 400°F (200°C).

• FLAME — often associated with inhalational injury and other concomitant

trauma. Flame burns tend to be deep dermal or full thickness. Flame burns are the second most common mechanism of thermal injury.

• CONTACT —In order to get a burn from direct contact, the object touched must either have been extremely hot or the contact was abnormally long. Burns from brief contact with very hot substances are usually due to industrial accidents. Contact burns tend to be deep dermal or full thickness.

THERMAL INJURIES

• FLASH - Explosions of natural gas, propane, butane, petroleum distillates, alcohols, and other combustible liquids, as well as electrical arcs cause intense heat for a brief time period. Flash burns generally have a distribution over all exposed skin, with the deepest areas facing the source of ignition. Are typically epidermal or partial thickness, their depth depending on the amount and kind of fuel that explodes

THERMAL INJURIES

ELECTRICAL INJURY• Some 3-4% of burn unit admissions are caused by

electrocution injuries (US data, 2005). • Mechanism:

– An electric current will travel through the body from one point to another, creating "entry" and "exit" points.

– The tissue between these two points can be damaged by the current.

– The amount of heat generated, and hence the level of tissue damage, is equal to 0.24x(voltage)2xresistance.

– The voltage is therefore the main determinant of the degree of tissue damage

CHEMICAL INJURY• Chemical injuries are usually results of industrial accidents but may occur

with household chemical products.• These burns tend to be deep, as the corrosive agent continues to cause

coagulative necrosis until completely removed. – Alkalis tend to penetrate deeper and cause worse burns than acids. – Cement is a common cause of alkali burns.

Chemical burn due to spillage of

sulphuric acid

BURN PATHOPHYSIOLOGY

The body’s response to a burn.

• Burn injuries result in both local and systemic responses

Local response

• Zone of coagulation—point of maximum damage., irreversible tissue loss due to protein coagulation

• Zone of stasis— with decreased tissue perfusion, tissue potentially salvageable

• Zone of hyperemia—outermost zone tissue perfusion is increased

Clinical image of burn zones. There is central necrosis, surrounded by the zones of stasis and of hyperaemia

LOCAL RESPONSE

• Loss of tissue in the zone of stasis will lead to the wound deepening as well as widening

SYSTEMIC RESPONSE

• release of cytokines and other inflammatory mediators at the site of injury has a systemic effect once the burn reaches 30% of total body surface area

SYSTEMIC RESPONSE

Electrical injuries• electric current travels through the body from

one point to another, creating “entry” and “exit” points.

• tissue between these 2 points can be damaged by the current

• amount of heat generated = level of tissue damage

• Voltage determines the degree of tissue damage

Electrical Injuries (Type)• Domestic Electricity (Low Voltage): cause

small, deep contact burns at the exit and entry sites

• True” high tension injuries: voltage ≥1000Vextensive tissue damage, often limb losslarge amount of soft and bony tissue necrosis• Flash injuries: tangential exposure to a high

voltage current arc but no current flow through the body

Classification of Burn Depths

• Partial thickness burns: do not extend through all skin layers

Superficial—affects the epidermis but not the dermis (such as sunburn), epidermal burn

Superficial dermal: extends through the epidermis into the upper layers of the dermis, associated with blistering

Deep dermal—extends through the epidermis into the deeper layers of the dermis but not through the entire dermis.

• Full thickness burns: extend through all skin layers into the subcutaneous tissues

Classification of Burn Depths

Assessment of Burn Depth

ASSESMENT OF BURN AREA

WALLACE RULE OF

NINES

Lund and Browder

chart

RESCUSCITATION REGIMEN

RESCUSCITATION REGIMEN

• The starting point for resuscitation is the time of injury, not the time of admission

• High tension electrical injuries require substantially more fluid (up to 9 ml×(burn area)×(body weight) in the first 24 hours) and a higher urine output (1.5-2 ml/kg/hour)

• regimens should be continuously adjusted• according to urine output and other physiological

parameters (pulse, blood pressure, and respiratory rate)

CRITERIA FOR REFERRAL TO A BURN CENTER• Second- and third-degree burns greater than 10%

TBSA in patients under 10 or over 50 years of age • Second- and third-degree burns greater than 20%

TBSA in other age groups • Second- and third-degree burns that involve the

face, hands, feet, genitalia, perineum, and major joints

• Third-degree burns greater than 5% TBSA in any age group

• Electrical burns, including lightning injury

CRITERIA FOR REFERRAL TO A BURN CENTER• Chemical burns • Inhalation injury • Burn injury in patients with pre-existing medical

disorders that could complicate management, prolong recovery, or affect mortality

• Any patients with burns and concomitant trauma (e.g., fractures, blast injury) where burn injury poses the greatest risk of morbidity or mortality.

• Burn injury in children who will require special social/emotional and/or long-term rehabilitative support, including cases involving suspected child abuse or substance abuse

REFERENCES

•Initial management of a major burn: II—assessment and resuscitation. Shehan Hettiaratchy, Peter Dziewulski. BMJ VOLUME 329 10 JULY 2004•Pathophysiology and types of burns. Shehan Hettiaratchy, Peter Dziewulski. BMJ VOLUME 328 12 JUNE 2004•American Burn Association. Hospital and Prehospital Resources for Optimal Care of Patients with Burn Injury: Guidelines for Development and Operation of Burn Centers. Journal of Burn Care and Rehabilitation. 1990; 11: 98-104.