# Burns: Assessment, Resuscitation, and Transfer Criteria

## Classification and Assessment

### Burn Depth

Burns are classified by depth of tissue injury. Superficial (first-degree) burns involve the epidermis only, presenting with erythema and pain without blisters — sunburn is the classic example — and heal in 3 to 5 days without scarring. Superficial partial-thickness (second-degree) burns extend through the epidermis into the superficial dermis, producing blisters with a moist, painful surface that blanches with pressure, and heal in 7 to 21 days with minimal scarring. Deep partial-thickness (second-degree) burns extend into the reticular dermis and are less painful due to nerve damage, have a mottled appearance, may not blanch, heal slowly with scarring, and may require grafting. Full-thickness (third-degree) burns destroy the entire dermis, presenting as white, waxy, or charred tissue that is painless (because nerves are destroyed) with a leathery texture, and always require grafting. Fourth-degree burns extend into subcutaneous tissue, muscle, fascia, or bone.

| Depth | Layer Involved | Appearance | Sensation | Healing | Grafting |
|-------|---------------|-----------|-----------|---------|----------|
| Superficial (1st) | Epidermis | Erythema, no blisters | Painful | 3–5 days, no scar | No |
| Superficial partial (2nd) | Papillary dermis | Blisters, moist, blanches | Very painful | 7–21 days, minimal scar | No |
| Deep partial (2nd) | Reticular dermis | Mottled, may not blanch | Decreased pain | Weeks, scarring | Often |
| Full-thickness (3rd) | Entire dermis | White/waxy/charred, leathery | Painless | Does not heal | Always |
| Fourth-degree | Subcutaneous, muscle, bone | Charred, exposed structures | Painless | Does not heal | Amputation/flap |

### TBSA Estimation

Total body surface area is estimated using the Rule of Nines for adults: the head accounts for 9 percent, each upper extremity 9 percent, the anterior trunk 18 percent, the posterior trunk 18 percent, each lower extremity 18 percent, and the perineum 1 percent. In pediatric patients, the head is proportionally larger (18 percent in infants) and the legs are smaller. The palm method uses the patient's palm including fingers to estimate approximately 1 percent TBSA, which is particularly useful for scattered burns. Only second-degree and deeper burns are included in the TBSA calculation — superficial burns are excluded. Overestimation of TBSA is the most common error and leads to over-resuscitation.

### Burn Center Referral Criteria (ABA)

The American Burn Association referral criteria include partial-thickness burns greater than 10 percent TBSA, full-thickness burns of any size, burns of the face, hands, feet, genitalia, perineum, or major joints, chemical or electrical burns, inhalation injury, burns with significant comorbidities, burns with associated trauma where the burn is the greater injury, children in hospitals without qualified pediatric capabilities, and burns requiring special social, emotional, or rehabilitative support.

## Fluid Resuscitation

### Parkland Formula

The Parkland formula calculates the total crystalloid volume for the first 24 hours as 4 mL multiplied by body weight in kilograms multiplied by the percent TBSA burned. The first half is given over 8 hours from the time of burn (not the time of presentation), and the second half is given over the subsequent 16 hours. Lactated Ringer's is the preferred solution over normal saline. The infusion rate is titrated to a urine output of 0.5 to 1 mL/kg/hr in adults and 1 to 2 mL/kg/hr in children.

### Fluid Creep

Over-resuscitation, known as "fluid creep," is increasingly recognized as a significant problem in major burns. Excess fluid leads to abdominal compartment syndrome, extremity compartment syndrome, pulmonary edema, and orbital compartment syndrome. A modified Parkland approach starts at 2 mL/kg/percent TBSA and titrates upward based on urine output. Colloid use after 12 to 24 hours may reduce total fluid requirements. Clinical endpoints — urine output, mental status, and hemodynamics — matter more than any formula.

### Resuscitation Pearls

Resuscitation should be initiated for burns greater than 20 percent TBSA in adults and greater than 10 percent in children. Two large-bore IVs are placed, through burned skin if necessary (access should not be delayed). A Foley catheter is placed for monitoring urine output. The Parkland formula should be treated as a starting point, not a fixed regimen — excessive fluid must be avoided.

## Inhalation Injury

### Pathophysiology

Thermal injury affects the upper airway (supraglottic structures), as heat is efficiently dissipated by the upper airway before reaching lower structures. Chemical injury from toxic combustion products (carbon monoxide, hydrogen cyanide, aldehydes, and particulates) damages the lower airway and parenchyma. Smoke inhalation is the leading cause of death in fire victims. Inhalation injury increases fluid requirements by 30 to 50 percent above Parkland calculations.

### Clinical Features

Historical clues include an enclosed space fire, prolonged exposure, and loss of consciousness. Examination findings include facial burns, singed nasal or facial hair, soot in the oropharynx, hoarseness, stridor, carbonaceous sputum, and wheezing. Stridor or hoarseness indicates impending airway obstruction, and early intubation should be performed before edema worsens. Progression of edema makes delayed intubation increasingly difficult and dangerous.

### Carbon Monoxide Poisoning

Carbon monoxide binds hemoglobin with 200 to 250 times the affinity of oxygen. Pulse oximetry is unreliable because it cannot distinguish carboxyhemoglobin from oxyhemoglobin, resulting in falsely normal readings. Carboxyhemoglobin levels above 3 percent in non-smokers and above 10 percent in smokers are abnormal, and levels above 25 percent are severe. Symptoms progress from headache, confusion, and nausea to seizures, coma, and cardiac ischemia. Treatment is 100 percent FiO2 via non-rebreather mask or intubation, which reduces the half-life of carboxyhemoglobin from 4 to 6 hours (on room air) to 60 to 90 minutes. Hyperbaric oxygen therapy is debated but generally considered for carboxyhemoglobin levels above 25 percent, loss of consciousness, cardiac ischemia, pregnancy, and persistent neurologic symptoms.

### Cyanide Poisoning

Cyanide is generated from combustion of synthetic materials such as plastics, wool, and silk. It should be suspected in patients with persistent metabolic acidosis and altered mental status despite carbon monoxide treatment. The classic finding is an elevated lactate (above 8 to 10 mmol/L) out of proportion to the clinical presentation. Treatment is hydroxocobalamin (Cyanokit) 5 g IV, which is preferred over sodium thiosulfate because it is safe, has a rapid onset, and does not cause methemoglobinemia. Sodium thiosulfate is an alternative with a slower onset.

## Specific Burn Types

### Electrical Burns

True tissue destruction in electrical burns is often far greater than the surface appearance suggests — this is described as the "iceberg phenomenon." Electrical current travels through the path of least resistance: nerves, then blood vessels, then muscle, then skin, then bone. Complications include cardiac arrhythmias (requiring ECG monitoring for 24 hours if high-voltage or any cardiac symptoms are present), rhabdomyolysis, compartment syndrome, solid organ injury, and vertebral compression fractures. Aggressive IV hydration is critical to prevent myoglobinuric renal failure, with a target urine output of 1 to 2 mL/kg/hr until myoglobinuria clears. Lightning strikes can cause cardiac arrest, with asystole being the most common initial rhythm. The principle of "reverse triage" applies — those who appear dead should be treated first because they may be in reversible arrest.

### Chemical Burns

Immediate and copious water irrigation should begin immediately without waiting for a specific neutralizing agent. Irrigation should continue for a minimum of 20 to 30 minutes, and alkali burns may require hours of irrigation. Alkali burns are generally worse than acid burns because liquefactive necrosis penetrates deeper into tissues, while acid burns cause coagulative necrosis that is self-limiting in depth. Hydrofluoric acid burns are uniquely dangerous because the fluoride ion binds calcium and magnesium, causing hypocalcemia, hypomagnesemia, and cardiac arrest. Treatment includes topical calcium gluconate gel, intradermal or intra-arterial calcium gluconate injection, and IV calcium for systemic toxicity. ECG monitoring for QT prolongation and dysrhythmias is essential.

### Tar Burns

Hot tar should be cooled with cold water first — removal of hot tar by peeling should not be attempted. Once cooled, the tar is dissolved with petroleum-based products such as mineral oil, Medi-Sol, or bacitracin.

## Wound Management

### Initial Wound Care

Burns should be cooled with cool running water for 20 minutes within 3 hours of injury, which is evidence-based. Ice must not be used because it causes vasoconstriction and worsens the injury. Loose, devitalized tissue and ruptured blisters are debrided. The management of intact blisters remains debated — there is no strong consensus, though large blisters and those over joints are often debrided. Burns are cleaned gently and a topical antimicrobial is applied.

### Topical Agents

Silver sulfadiazine is the traditional agent with broad-spectrum coverage, but it can cause leukopenia, delays wound healing, and is painful on application. Bacitracin with petroleum is used for facial burns and superficial burns. Mafenide acetate (Sulfamylon) penetrates eschar and is used for ear burns to prevent chondritis, but it is painful and can cause metabolic acidosis as a carbonic anhydrase inhibitor. Silver-impregnated dressings (such as Mepilex Ag and Aquacel Ag) are modern options that require fewer dressing changes and cause less pain.

| Agent | Indication | Advantage | Disadvantage |
|-------|-----------|-----------|--------------|
| Silver sulfadiazine | General partial-thickness burns | Broad-spectrum | Leukopenia, delays healing, painful |
| Bacitracin/petroleum | Face, superficial burns | Gentle, inexpensive | Limited spectrum |
| Mafenide acetate (Sulfamylon) | Ear burns, eschar penetration | Penetrates eschar | Painful, metabolic acidosis (CA inhibitor) |
| Silver-impregnated dressings | Partial-thickness burns | Fewer dressing changes, less pain | Cost |

### Escharotomy

Escharotomy is indicated for circumferential full-thickness burns with compromised circulation or ventilation. In the extremities, the indication is impaired distal pulses or increasing compartment pressure. In the chest, the indication is impaired ventilation with decreased tidal volumes or rising peak pressures. The incision is made through the eschar only (not into viable tissue) along mid-lateral and mid-medial lines. Anesthesia is not required in full-thickness burns because the tissue is insensate.

<image>A diagram showing the Rule of Nines for burn TBSA estimation in adults and children. The adult figure shows: head and neck 9%, each upper extremity 9%, anterior trunk 18%, posterior trunk 18%, each lower extremity 18%, and perineum 1%. The pediatric figure (infant) shows the modified percentages: head 18%, each upper extremity 9%, anterior trunk 18%, posterior trunk 18%, each lower extremity 14%, and perineum 1%. A hand silhouette is shown alongside indicating that the patient's palm plus fingers equals approximately 1% TBSA.</image>

<image>A cross-sectional diagram of skin showing burn depth classification. The diagram shows layers from top to bottom: epidermis, papillary dermis, reticular dermis, subcutaneous fat, muscle, and bone. Color-coded zones indicate: superficial (first degree) limited to epidermis; superficial partial thickness extending into papillary dermis with blisters; deep partial thickness extending into reticular dermis; full thickness destroying the entire dermis; and fourth degree extending into subcutaneous tissue and beyond. Each zone is annotated with clinical features: sensation, appearance, healing time, and scarring potential.</image>

<image>An illustration of escharotomy incision lines on a human body. Anterior view showing incision lines along the mid-axillary lines of the trunk, mid-lateral and mid-medial lines of each extremity, and along the ulnar and radial borders of the hands. An inset shows a cross-section through a circumferentially burned extremity, demonstrating how the constricting eschar compresses underlying structures and how the escharotomy incision releases pressure by allowing the tissue to expand.</image>

## Clinical Pearls

Only partial-thickness and deeper burns are counted in TBSA — superficial burns are excluded from Parkland calculations. The Parkland formula is a starting point, not a prescription, and must be titrated to urine output while avoiding fluid creep. Inhalation injury presenting with stridor or hoarseness mandates early intubation — waiting for respiratory failure is dangerous because airway edema worsens rapidly. Pulse oximetry is unreliable in carbon monoxide poisoning, and a carboxyhemoglobin level should always be obtained in fire and smoke exposure patients. Cyanide toxicity should be suspected when patients have persistent metabolic acidosis and altered mental status despite carbon monoxide treatment, and hydroxocobalamin should be given. Electrical burns are the tip of the iceberg, with deep tissue injury often far more extensive than the surface wound suggests. Chemical burns should be irrigated immediately and copiously with water — the search for specific neutralizing agents should not delay treatment. Hydrofluoric acid burns are uniquely dangerous because hypocalcemia and cardiac arrest can occur, requiring treatment with calcium gluconate. Circumferential full-thickness burns of the chest can restrict ventilation, and escharotomy may be needed emergently.

## References

- Baxter CR, Shires T. Physiological response to crystalloid resuscitation of severe burns. *Ann NY Acad Sci*. 1968;150:874-894.
- Saffle JI. The phenomenon of fluid creep in acute burn resuscitation. *J Burn Care Res*. 2007;28:382-395.
- American Burn Association. Burn center referral criteria. *J Burn Care Rehabil*. 2001;22:33-38.
- Weaver LK, et al. Hyperbaric oxygen for acute carbon monoxide poisoning. *NEJM*. 2002;347:1057-1067.
- Endorf FW, Ahrenholz D. Burn management. *Curr Opin Crit Care*. 2011;17:601-605.