• Clinical science

Burns

Abstract

Burns are injuries to tissue caused by heat, chemicals, and/or radiation. The two factors that influence the severity of a burn are its depth and the surface area involved. Accordingly, burns are classified into four grades based on the depth of tissue involvement. Lund-Browder charts are used to calculate the surface area involved. Massive tissue necrosis, which occurs with severe burns, results in sepsis, shock, and sequential organ failure (see SOFA score for details). In the case of severe burns, patients should be intubated, given supplemental oxygen and resuscitated with IV fluids. Parkland's formula is commonly used to calculate initial fluid requirement, but fluids should be adjusted to maintain clinical stability and appropriate urine output. Pulse oximetry, blood gas analysis, and measurement of electrolyte and creatinine levels are important diagnostic procedures for patients with severe burns. In the case of circumferential burns around limbs, peripheral pulses and capillary refill can be used to detect perfusion. Escharotomy should be performed in order to treat compartment syndrome and prevent acute limb ischemia. First and second-degree burns can be treated with antiseptic ointment and dressings. Treatment of third and fourth-degree burns involves debridement of necrotic tissue followed by skin graft or a tissue transfer via flap. Burn wounds tend to become infected and large, severe burns tend to be fatal injuries. The most common causes of death following burns are shock, sepsis, and respiratory failure.

Etiology

  • Thermal injury (e.g., scalding, contact with a hot surface, fires)
  • Non-thermal injury: radiation, chemical burns, electrical burns[1]

Although most cases of burns are the result of accidental injury, non-accidental injury must always be suspected in vulnerable populations, including children and the elderly!

Pathophysiology

Local effects

  • Local changes at the burn site[1] (Jacobson's model of the burn wound)
    • Zone of coagulation: a central zone of irreversible, coagulative necrosis
    • Zone of stasis: surrounds the central zone of coagulation and is comprised of damaged but viable tissue with decreased perfusion
    • Zone of hyperemia: surrounds the zone of stasis and is characterized by inflammation and increased blood flow

A burn wound is a dynamic wound. If resuscitation and/or wound care are not adequate, the zone of stasis becomes irreversibly damaged and the depth of the burn increases!

  • Almost all burns are colonized by bacteria.[2]
  • Eschars can cause constrictive effects.[3]
    • Significant eschar on chest or neck → restricts chest excursionasphyxia
    • Circumferential eschars → loss of skin elasticity → impaired blood flow and/or compartment syndrome (caused by an accumulation of fluids) → acute ischemia distal to the eschar

Systemic effects

References:[2]

Burn severity

The two factors that influence the severity of a burn are its depth and the surface area involved.

Depth of a burn

Burns are classified into four grades based on their depth, the degree of pain associated with them, and other clinical features (redness, blister formation).

In cases of severe, deep burns, pain may be absent as a result of damage to sensory nerve endings!

Degree of burns[4]

Depth of tissue damage

Symptoms[5]

Healing process

1st degree (superficial burn)

  • Pain
  • Erythema
  • Swelling
  • The burn wound blanches on applying pressure and refills rapidly
  • Healing within 3–6 days without scarring

2nd degree

2a (superficial partial-thickness burn)
  • Healing within 1–3 weeks with hypopigmentation/hyperpigmentation but without scarring
2b (deep partial-thickness burn)
  • Deeper layers of the dermis.
  • Minimal pain
  • Mottled skin with red and/or white patches
  • Vesicles/bullae
  • The burn wound does not blanch on applying pressure.
  • Healing takes 3 weeks or longer and results in scar formation

3rd degree (full thickness burn)

  • The burn does not heal by itself.

4th degree

  • Deeper structures (muscles, fat, fascia, and bones)
  • Charred tissue
  • The tissue is dead and requires amputation.

Extent of burns (surface area involved)

  • Lund-Browder chart
    • Age-specific charts are used to calculate the surface area covered by a burn.
    • Most accurate method for both adults and children
  • Wallace's rule of nines
    • A quick but reliable method for estimating the surface area covered by burns in the case of adults.
    • The rule of nines is unreliable among children.
Body surface area
Segment Adult Small child Infant
Head 9% 16% 18%
Trunk 36% (4 x 9%)
Arms 18% (2 x 9%)
Thighs 18% (2 x 9%) 13.5% 14.5%
Lower legs and feet 18% (2 x 9%) 13.5% 14.5%
Genital region 1%
  • Palm rule
    • The palm accounts for 1% of the total body area.
    • It is the least reliable method.

Clinical features

  • Clinical features of shock[1] (e.g., hypotension, poor urine output)
  • Clinical features of ARDS (e.g., dyspnea)
  • Inhalation injury should be suspected when any of the following are present:[370]
    • History of being trapped in a confined space.
    • Facial burns, singed eyebrows and/or nose hair, evidence of soot on the face or in the airway
    • Stridor, dysphonia
    • Extensive burns
  • In case of circumferential burns around limbs → compartment syndrome: clinical features of acute limb ischemia (e.g., weak/absent pulse, paresthesias, pallor in the affected limb)
  • In case of circumferential burns around abdomen → abdominal compartment syndrome: impaired function fo nearly every organ system (e.g., oliguria, acute pulmonary decomensation, hypoperfusion) and signs of increased intrabdominal pressure (jugular venous distension, hypotension, tachycardia)

In the case of adults, shock sets in when burns involve > 15% of the body surface. Burns that involve 50–70% of the body surface are usually lethal. In children, signs of shock appear with > 10% involvement of the body surface and 60–80% body surface involvement is lethal!

Diagnostics

Burn severity is based upon clinical history and physical examination, but further testing is conducted to monitor for complications and guide therapy.

Treatment

Immediate measures in case of severe burns: Think “ABCs”--Airway, Breathing, Circulation

  • Airway management: Intubation and high flow oxygen therapy is indicated if an inhalation injury is suspected; [7] or if burns involve more than 30–40% of the body surface; . Don't delay intubation if needed, as fluid resuscitation can increase laryngeal swelling, which will complicate intubation
  • Begin initial fluid resuscitation with crystalloids, usually lactated Ringer's solution (RL)[7]
    • In adults: Parkland formula is used to guide initial fluid therapy; : the volume of lactated Ringer's solution to be administered within a period of 24 h = 4 mL/kg x % of total body surface involved in burn x body weight (in kg)
    • In children: initial fluid therapy for a 24 hour period is the Parkland formula + 24 h maintenance fluid requirements
    • Modified Brooke's formula may be used as an alternative to Parkland's formula: volume of lactated Ringer's solution to be administered within a period of 24 h = 2 mL x % of body surface involved in burn x body weight (in kg)
    • Note that this is an INITIAL estimate for fluid requirements: fluid therapy should be modified to achieve a urine output of > 0.5 mL/kg/hr in adults and > 1 mL/kg/hr in children.
  • Remove any burnt clothing[7], cool the burnt area with cool running water or saline-soaked gauzes. Do NOT use ice or ice water! Cover the wound with a sterile dressing.
    • Core body temperature should be monitored for hypothermia; if body temperature < 35°C, warm IV fluids can be given
    • Cool with caution or not at all in patients with burns involving >10% BSA as they are particularly vulnerable to hypothermia.[7]

Patients with burns who cannot take fluids orally also require maintenance fluids. Parkland's formula does not include the daily maintenance fluid requirement!

Because fluid resuscitation can worsen laryngeal edema, intubation should be performed before fluid resuscitation![7]

Additional measures

Management based on degree

  • 1st and 2nd-degree burns
    • Irrigation
    • Topical moisturizers (e.g., calamine lotion) or aloe vera-based gels: relieve symptoms of 1st-degree burns
    • Consider antiseptic ointments (e.g., silver sulfadiazine, mafenide) or topical antibiotics (bacitractin; triple antiobitic ointments are a combination of bactracin neomycin, polymyxin B)[7]
      • For periorbital or periocular burns, topical antibiotics (e.g., bacitracin, neomycin, or erythromycin) are preferred over silver sulfadiazine, which may be irritating and cause ocular toxicity.
    • Deroofing bullae/vesicles
    • Dressing is indicated in partial thickness (2nd-degree) burns.
  • 3rd and 4th-degree burns
    • Early debridement of burnt, necrotic tissue
    • Method of tissue coverage varies depending on the specific burn characteristics. Options include:
    • Topical antibiotics (e.g., silver sulfadiazine, bacitracin, neomycin)

Burn eschars: specific measures

  • For circumferential burn[7]
    • Perform a doppler test, as well as check the capillary refill time, peripheral pulses, sensations, and pulse oximetry in the limb hourly for 24–48 hours
    • If NO impending vascular/respiratory compromise or compartment syndrome:
      • Elevate the lower limb or torso
      • Perform range of motion exercises as tolerated
    • If vascular/respiratory compromise or compartment syndrome is impending or has occurred:
  • For chest/neck eschars:
    • If respiratory compromise impending or has occured → escharotomy

Small superficial and superficial partial-thickness burns may be treated on an outpatient basis with paraffin gauze, antiseptic ointment, and analgesics!

Chemical burns: specific measures

  • Immediate, copious irrigation of all areas of exposure with water, prior to or on the way to the hospital.
    • Once in the hospital, irrigation should be continued until the pH normalizes

Complications

We list the most important complications. The selection is not exhaustive.