Residency · Residency · General Surgery

Burns: Initial Assessment and Surgical Management

Introduction

Burn injuries affect over 450,000 patients annually in the United States, with approximately 40,000 requiring hospitalization. Modern burn care has dramatically improved survival through advances in resuscitation, wound management, critical care, and reconstructive techniques. The general surgeon must understand the pathophysiology of burn injury, principles of fluid resuscitation, indications for surgical intervention, and management of burn-specific complications.

Burn Pathophysiology

Zones of Injury (Jackson's Model)

The zone of coagulation is the central area of irreversible tissue necrosis from direct thermal injury where protein denaturation is complete. The zone of stasis is the surrounding area of decreased perfusion containing potentially salvageable tissue; inflammatory mediators, edema, and inadequate resuscitation can convert this zone to necrosis within 24-48 hours. The zone of hyperemia is the outermost zone with increased blood flow due to inflammatory vasodilation; this tissue will recover unless complicated by infection or prolonged hypoperfusion.

Systemic Response

Burn shock is a unique combination of distributive and hypovolemic shock. Massive capillary leak occurs in the first 18-24 hours, with peak edema at 12-24 hours. Inflammatory mediator release (histamine, prostaglandins, thromboxane, and cytokines) causes systemic capillary permeability even in unburned tissue when burn size exceeds 20-30% total body surface area. The hypermetabolic response can increase the metabolic rate 100-200% above baseline in major burns, with catecholamine surge, insulin resistance, and muscle catabolism persisting for months to years. Burns cause both innate and adaptive immune dysfunction, predisposing patients to sepsis and opportunistic infections.

Initial Assessment

Primary Survey Modifications

The airway assessment must include evaluation for inhalation injury. Signs include facial burns, singed nasal hair, carbonaceous sputum, hoarseness, stridor, and a history of enclosed-space fire. Early intubation is critical because airway edema progresses rapidly. For breathing, circumferential chest burns may restrict ventilation and require emergent escharotomy. Circulation management requires large-bore IV access, preferably through unburned skin, with intraosseous access if IV access is unobtainable.

Carbon monoxide poisoning must be considered in all fire victims. Pulse oximetry is unreliable because SpO2 is falsely elevated. A carboxyhemoglobin level should be obtained, and treatment is 100% FiO2. Hyperbaric oxygen is considered for COHb levels above 25%, neurological symptoms, or pregnancy. Cyanide toxicity should be suspected in enclosed-space fires involving synthetic materials when persistent metabolic acidosis and elevated lactate are present despite CO correction. Treatment is hydroxocobalamin (Cyanokit).

Burn Depth Classification

Superficial (first degree) burns involve the epidermis only, present with erythema and pain without blistering, and heal in 3-5 days, such as sunburn. Superficial partial thickness (second degree) burns involve the epidermis and superficial dermis, present with blisters over a moist pink base that is painful with brisk capillary refill, and heal in 10-14 days with minimal scarring. Deep partial thickness (second degree) burns involve the epidermis and deep dermis, appear mottled pink or white with decreased sensation and sluggish capillary refill, heal in 3-8 weeks with significant scarring, and often require excision and grafting. Full thickness (third degree) burns destroy the entire dermis, appear white, waxy, leathery, or charred, are insensate, and require excision and grafting. Fourth degree burns extend into subcutaneous fat, fascia, muscle, or bone and require complex reconstruction or amputation.

<image>Cross-sectional illustration of skin layers showing the four depths of burn injury from superficial through fourth degree, with corresponding clinical appearance descriptions and expected healing times for each depth</image>

Burn Size Estimation

The Rule of Nines divides the adult body surface area into regions of 9% or multiples: the head is 9%, each upper extremity is 9%, each lower extremity is 18%, the anterior trunk is 18%, the posterior trunk is 18%, and the perineum is 1%. The Lund-Browder chart is an age-adjusted body surface area map that is more accurate, especially in children where head and lower extremity proportions differ from adults. The palm method uses the patient's palm including fingers to represent approximately 1% TBSA, which is useful for scattered or irregular burns. Only partial thickness and full thickness burns are included in the TBSA calculation for resuscitation purposes; superficial burns are excluded.

Fluid Resuscitation

The Parkland formula calculates 4 mL multiplied by body weight in kilograms multiplied by percent TBSA burned of lactated Ringer's solution in the first 24 hours, with half given in the first 8 hours from the time of burn and the remaining half over the next 16 hours. The modified Brooke formula uses 2 mL per kilogram per percent TBSA and is increasingly preferred to reduce over-resuscitation. Urine output is the primary endpoint of adequate resuscitation, targeting 0.5-1 mL/kg/hr in adults and 1-2 mL/kg/hr in children. Over-resuscitation ("fluid creep") is a recognized problem that can lead to abdominal compartment syndrome, extremity compartment syndrome, pulmonary edema, and cerebral edema. Colloid administration (5% albumin) may begin after 12-24 hours when capillary integrity improves, allowing reduction in crystalloid volume. Patients requiring resuscitation include those with burns greater than 20% TBSA in adults or greater than 10% TBSA in children or elderly patients.

<image>Anterior and posterior human body diagrams illustrating the Rule of Nines for adult burn size estimation with percentage labels for each body region, alongside a Lund-Browder chart showing age-adjusted values for pediatric patients</image>

Inhalation Injury

Upper airway injury involves direct thermal injury to supraglottic structures. Heat is efficiently dissipated by the nasopharynx and oropharynx, so subglottic thermal injury is rare except with steam inhalation. Lower airway injury is a chemical injury from inhaled combustion products (aldehydes, acrolein, hydrogen chloride) that causes bronchospasm, mucosal sloughing, cast formation, and ARDS. Diagnosis is made with fiber-optic bronchoscopy, the gold standard, which reveals mucosal erythema, edema, carbonaceous deposits, and mucosal necrosis. Management is supportive and includes aggressive pulmonary toilet, bronchodilators, nebulized heparin and N-acetylcysteine protocols, and mechanical ventilation with lung-protective strategies as needed. Inhalation injury increases fluid requirements by 30-50% above calculated formulas and significantly increases mortality.

Surgical Management

Escharotomy

Escharotomy is indicated for circumferential full-thickness burns of the extremities causing vascular compromise or of the chest and abdomen causing respiratory compromise. The technique involves full-thickness incision through the eschar to the subcutaneous fat along the mid-lateral and mid-medial lines of the extremity. For the chest, bilateral anterior axillary line incisions are connected by a transverse subcostal incision. Escharotomy must be performed within hours of injury as edema progresses, and delayed escharotomy risks limb loss.

Excision and Grafting

Early excision of burn eschar within 72 hours of injury reduces sepsis, hospital stay, and mortality compared to serial debridement. Tangential excision involves sequential shaving of burned tissue with a Weck blade or dermatome until punctate bleeding from viable dermis is encountered. Fascial excision, which removes tissue to the level of the fascia, is used for very deep burns or when tangential excision results in excessive blood loss; it produces a reliable wound bed but yields a poorer cosmetic result. Operative blood loss during tangential excision can be significant (100-200 mL per percent TBSA excised), and topical epinephrine, thrombin, tourniquet use, and tumescent injection help minimize bleeding.

Autograft using split-thickness skin graft harvested at 8-12/1000 inch thickness is the definitive coverage. Meshing the graft (1:1.5, 1:3, or 1:4) allows coverage of larger areas and drainage of fluid, though sheet grafts are preferred for cosmetically sensitive areas such as the face and hands. Temporary coverage options include cadaveric allograft (homograft), xenograft (porcine), synthetic skin substitutes (Integra, Biobrane), and cultured epidermal autograft for massive burns with limited donor sites.

<image>Stepwise surgical illustration showing tangential excision of burn eschar with a Weck blade, followed by application of meshed split-thickness skin graft secured with staples over a viable wound bed</image>

Burn Center Referral Criteria (American Burn Association)

Referral to a burn center is indicated for partial thickness burns greater than 10% TBSA, burns involving the face, hands, feet, genitalia, perineum, or major joints, full thickness burns of any size, electrical burns including lightning injury, chemical burns, inhalation injury, burns in patients with significant comorbidities, burns with concomitant trauma where the burn poses the greatest risk, burns in children at hospitals without qualified pediatric capability, and burns requiring special social, emotional, or rehabilitative intervention.

Complications

Burn wound infection is the most common cause of death in burn patients. It should be suspected when the wound changes character (deepening, discoloration, rapid eschar separation), and wound biopsy with more than 10^5 organisms per gram of tissue confirms invasive infection. Sepsis is challenging to diagnose because burn patients have a baseline SIRS response; modified burn sepsis criteria include temperature above 39 or below 36.5 degrees Celsius, tachycardia above 110, tachypnea above 25, and clinical evidence of infection. Abdominal compartment syndrome from massive fluid resuscitation is diagnosed by bladder pressure above 20 mmHg with organ dysfunction and requires decompressive laparotomy. Curling's ulcer, a stress gastric or duodenal ulceration, is prevented with proton pump inhibitors or H2 receptor blockers.

Key Clinical Pearls

Early intubation for suspected inhalation injury is life-saving; waiting for clinical deterioration is dangerous because airway edema progresses rapidly and can preclude intubation. The Parkland formula is a starting point, not a fixed prescription, and fluids must be titrated to urine output while guarding against fluid creep. Early tangential excision and grafting within 72 hours is the standard of care for deep partial thickness and full thickness burns. Circumferential full-thickness burns require urgent escharotomy and should not be delayed for transport. Carbon monoxide poisoning causes falsely normal SpO2 readings, and a carboxyhemoglobin level should always be obtained in fire victims.

References

1. Jeschke MG, van Baar ME, Choudhry MA, et al. Burn injury. Nat Rev Dis Primers. 2020;6(1):11.
2. Cancio LC, Lundy JB, Sheridan RL. Evolving changes in the management of burns and environmental injuries. Surg Clin North Am. 2012;92(4):959-986.
3. Greenhalgh DG. Management of burns. N Engl J Med. 2019;380(24):2349-2359.
4. American Burn Association. Advanced Burn Life Support Course Provider Manual. 2018 Update.

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