What are the zones of burns?

The Three Zones of Burns

Burns are characterized by three distinct zones: the zone of coagulation (central necrosis), the zone of stasis (potentially salvageable tissue), and the zone of hyperemia (inflammatory response).

Zone of Coagulation

• The central zone of coagulation represents the area of direct thermal injury where cell death is complete and tissue is irreversibly damaged 1
• This area appears as eschar (dead tissue) and is characterized by protein denaturation and coagulation necrosis 1
• The zone of coagulation is definitely lost and requires eventual debridement and grafting 1

Zone of Stasis

• Surrounding the zone of coagulation is the zone of stasis, characterized by a mix of viable and nonviable cells, decreased tissue perfusion, and capillary vasoconstriction 2
• This zone is potentially salvageable but at high risk of progressing to necrosis within the first week after injury if not properly managed 1
• Both early apoptosis and delayed necrosis contribute to injury progression in this zone, with necrosis playing a larger role in the progression of damage 3
• Pathophysiological changes in this zone include:
  • Decreased blood flow due to vasoconstriction
  • Microvascular thrombosis
  • Progressive edema formation
  • Inflammatory cell infiltration 2, 3

Zone of Hyperemia

• The outermost zone of hyperemia is characterized by increased blood flow due to vasodilation and inflammatory response 1
• This zone typically recovers spontaneously without intervention as the pathophysiological changes are reversible 1
• It represents the body's normal inflammatory response to injury with increased blood flow and delivery of inflammatory mediators 1

Clinical Significance

• Proper burn management focuses on salvaging the zone of stasis to prevent further tissue loss and minimize the extent of injury 2
• Therapeutic interventions that can potentially save the zone of stasis include:
  • Adequate fluid resuscitation to maintain microcirculation 4
  • Topical negative pressure therapy to reduce edema formation and preserve microcirculation 4
  • Anti-inflammatory agents like pentoxifylline that can enhance burn wound healing by increasing epithelialization and decreasing necrotic area 2

Common Pitfalls in Burn Assessment

• Underestimating the depth and extent of burns based on initial appearance, as the zone of stasis may progress to necrosis over time 3
• Failure to recognize that visible skin damage may not correlate with the extent of injury, particularly in electrical burns 5
• Inadequate fluid resuscitation leading to increased conversion of the zone of stasis to necrosis 4

Understanding these three zones is crucial for proper burn assessment and management, as it guides treatment decisions aimed at limiting burn wound progression and optimizing outcomes for patients with thermal injuries 1, 2.