Phases of burn wound healing
The way a burn wound heals depends on many factors, including its cause (etiology), pathophysiology, infection and treatment. Burn wounds heal differently from trauma wounds in various ways, and therefore treatment is different.
In extensive burn injuries, capillaries become more permeable and this means plasma is lost from the circulation. This leads to hypovolemic shock if it is not treated properly.
Because the skin is damaged, it no longer functions as a barrier. This compromises the immune system and increases the risk of infection, bacteremia and sepsis.
These differences aside, all wounds heal in a dynamic process that has three main phases: inflammatory, proliferative and remodeling.
1 Inflammatory phase
Time of injury to day 4
The main goals of this phase are to prevent infection during healing, to degrade necrotic tissue and to activate signals required for wound repair.
Key components of this phase are increased vasodilatation and fluid extravasation.
Neutrophils and monocytes infiltrate the site of injury, initiating an immune response. This immune response is sustained by the recruitment of macrophages by cytokines.
In chronic wounds, normal healing progression usually becomes arrested in the inflammatory stage. The presence of necrotic tissue, foreign material, and bacteria result in the abnormal production of matrix metalloproteases, which alter the balance of inflammation and impair the function of the cytokines.
2 Proliferative phase
Day 4 to week 2-6
In this phase, keratinocytes and fibroblasts are activated by cytokines and growth factors. Keratinocytes migrate over the wound to restore the vascular network and assist closure. Fibroblasts produce collagen that deposits in the wound.
3 Remodeling phase
Up to 18 months after wound closure
In this phase, collagen in the wound matures and strengthens.