• Clinical science

Burns

Summary

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. Different formulas exist 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

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!References:[1]

Pathophysiology

Local effects

  • Almost all burns are colonized by bacteria.
  • Eschars can cause constrictive effects.
    • Significant eschar on chest or neck → restricts chest excursion → asphyxia
    • Circumferential escharsloss 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:[3][1][2]

Burn severity

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

Depth of tissue damage

Symptoms

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

Extent of burns (surface area involved)

  • 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%) 14.5% 13.5%
Lower legs and feet 18% (2 x 9%) 14.5% 13.5%
Genital region 1%

References:[4][5]

Clinical features

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! References:[1][6]

Diagnostics

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

References:[6][7][8]

Treatment

Immediate measures in case of severe burns: Think “ABCsAirway, Breathing, Circulation

  • Airway management: intubation and high flow oxygen therapy is indicated if an inhalation injury is suspected 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)
    • In adults and children ≥ age 14
      • Parkland formula was traditionally used to guide initial fluid therapy: the volume of lactated Ringer's solution to be administered within a period of 24 h = 4 mL x % of total body surface involved in 2nd and 3rd-degree burns x body weight (in kg)
      • Current recommendations by the ATLS and the American Burn Association: volume of lactated Ringer's solution to be administered within a period of 24 h = 2 mL x % of body surface involved in 2nd and 3rd-degree burns x body weight (in kg)
      • Half of this volume should be administered within the first 8 hours and the remaining half within the next 16 hours
    • In children < age 14
    • 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/h in adults and 1 mL/kg/h in children (< 30 kg).

Because of studies demonstrating serious complications from over-resuscitation (e.g., pleural effusions and compartment syndrome), the ATLS and American Burn Association now recommend only giving half of the fluid resuscitation volume that is calculated by the Parkland formula in adults; i.e., 2 mL x %TBSA x weight (kg) instead of 4 mL). The volume is still given over 24 hours, with one half given in the first 8 hours and the remaining half over the next 16 hours.

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

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

  • Remove any burnt clothing
  • 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.

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)
      • 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

Burn eschars: specific measures

  • For circumferential burn
  • 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

References:[6][9][10]

Complications

References:[6][4]

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