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Wound healing
Chapter
46
Wound healing David G. Greenhalgh
Chapter contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 578 Types of burns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 578 Types of tissue repair . . . . . . . . . . . . . . . . . . . . . . . . . . 579 Scar formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 581 Contraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 584 Types of wound coverage . . . . . . . . . . . . . . . . . . . . . . 584 Factors affecting wound healing . . . . . . . . . . . . . . . . . 587 Methods of stimulating wound healing . . . . . . . . . . . 589 Scar control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 590 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 592
Introduction The ultimate goals of all burn team members are to heal the patient’s wounds with the least scarring and to maximize the functional and cosmetic outcome. The management of the burn wound depends on the depth and extent of the injury. Those wounds that are superficial need to re-epithelialize. Smaller but deep wounds heal by scar formation and contraction. These processes are beneficial at times but detrimental at other times. Understanding how these wounds heal will help with choosing an appropriate treatment. Larger wounds require grafting. By understanding how a graft heals, one can optimize the outcome. It is clear that all patients with burns greater than 20–25% total body surface area (TBSA) develop systemic changes that influence their survival. The burn wound is a major source of inflammatory mediators that lead to hypermetabolism, muscle wasting and, potentially, dysfunction of multiple organ systems. The best way to treat these systemic problems is to eliminate the source of the inflammatory mediators by expeditiously removing the source of the mediators and covering the wound. The strategies for covering these massive wounds will be discussed in this chapter. The factors that influence wound healing will also be described. Finally, much of our time is devoted to the management of scars. While relatively little is known about reducing scar formation, more options are available to us compared to the past. Hopefully, we will gain further insights into the control of scar formation in the future. There are several basic principles that the burn team must remember when treating a wound: 578
1. The goal is to maximize the functional and cosmetic outcome of the burn. 2. Optimizing initial wound care will minimize the need for scar management and reconstructive surgery. (Do it right from the start.) 3. If a burn heals within 2 weeks, then scarring is minimal. If the wound has not healed within 2 weeks, then grafting is probably indicated. 4. Topical agents do heal a wound but, instead, reduce infection risks. In addition, they do not eliminate bacteria. Target the topical agent for the wound type and the likely bacterial flora. 5. Make treatment simple (especially in the outpatient setting): • Sterile techniques are unnecessary. Use clean techniques. • The patient may get into the shower or tub. • Caregivers should wash their hands and use clean barriers (gowns, gloves) in the inpatient setting. • At home, barrier techniques are probably not indicated. Hand washing is still important. • Try to minimize pain. The goal of this chapter is to describe the types of wound healing in order to develop better principles of wound management that will lead to the best possible outcome for burn patients.
Types of burns In order to optimally treat burn wounds, one must fi rst know the types of burn injuries that exist. The type of healing that is involved in each type of wound changes depending on wound depth. Skin can be simply considered to consist of two major components, the epidermis and dermis (Figure 46.1). The major function of the epidermis is to keep invading organisms ‘out’ and keep water ‘in.’ At the base of the epidermis are the basal cells, which are the only keratinocytes of the epidermis that can proliferate and migrate. These cells are attached to a basement membrane that separates the epidermis from the dermis. The basal cells differentiate as they leave the basement membrane and eventually die and slough in the more superficial layers of the epithelium. The detachment, migration away from the basement membrane, differentiation, and sloughing is the normal life cycle of the keratinocytes. The dermis adds the strength to the skin, since it is made of collagen and other extracellular matrix (ECM) proteins. The dermis also contains a vascular and neural plexus. The vascular plexus
46
Wound healing David G. Greenhalgh
Chapter contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 578 Types of burns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 578 Types of tissue repair . . . . . . . . . . . . . . . . . . . . . . . . . . 579 Scar formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 581 Contraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 584 Types of wound coverage . . . . . . . . . . . . . . . . . . . . . . 584 Factors affecting wound healing . . . . . . . . . . . . . . . . . 587 Methods of stimulating wound healing . . . . . . . . . . . 589 Scar control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 590 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 592
Introduction The ultimate goals of all burn team members are to heal the patient’s wounds with the least scarring and to maximize the functional and cosmetic outcome. The management of the burn wound depends on the depth and extent of the injury. Those wounds that are superficial need to re-epithelialize. Smaller but deep wounds heal by scar formation and contraction. These processes are beneficial at times but detrimental at other times. Understanding how these wounds heal will help with choosing an appropriate treatment. Larger wounds require grafting. By understanding how a graft heals, one can optimize the outcome. It is clear that all patients with burns greater than 20–25% total body surface area (TBSA) develop systemic changes that influence their survival. The burn wound is a major source of inflammatory mediators that lead to hypermetabolism, muscle wasting and, potentially, dysfunction of multiple organ systems. The best way to treat these systemic problems is to eliminate the source of the inflammatory mediators by expeditiously removing the source of the mediators and covering the wound. The strategies for covering these massive wounds will be discussed in this chapter. The factors that influence wound healing will also be described. Finally, much of our time is devoted to the management of scars. While relatively little is known about reducing scar formation, more options are available to us compared to the past. Hopefully, we will gain further insights into the control of scar formation in the future. There are several basic principles that the burn team must remember when treating a wound: 578
1. The goal is to maximize the functional and cosmetic outcome of the burn. 2. Optimizing initial wound care will minimize the need for scar management and reconstructive surgery. (Do it right from the start.) 3. If a burn heals within 2 weeks, then scarring is minimal. If the wound has not healed within 2 weeks, then grafting is probably indicated. 4. Topical agents do heal a wound but, instead, reduce infection risks. In addition, they do not eliminate bacteria. Target the topical agent for the wound type and the likely bacterial flora. 5. Make treatment simple (especially in the outpatient setting): • Sterile techniques are unnecessary. Use clean techniques. • The patient may get into the shower or tub. • Caregivers should wash their hands and use clean barriers (gowns, gloves) in the inpatient setting. • At home, barrier techniques are probably not indicated. Hand washing is still important. • Try to minimize pain. The goal of this chapter is to describe the types of wound healing in order to develop better principles of wound management that will lead to the best possible outcome for burn patients.
Types of burns In order to optimally treat burn wounds, one must fi rst know the types of burn injuries that exist. The type of healing that is involved in each type of wound changes depending on wound depth. Skin can be simply considered to consist of two major components, the epidermis and dermis (Figure 46.1). The major function of the epidermis is to keep invading organisms ‘out’ and keep water ‘in.’ At the base of the epidermis are the basal cells, which are the only keratinocytes of the epidermis that can proliferate and migrate. These cells are attached to a basement membrane that separates the epidermis from the dermis. The basal cells differentiate as they leave the basement membrane and eventually die and slough in the more superficial layers of the epithelium. The detachment, migration away from the basement membrane, differentiation, and sloughing is the normal life cycle of the keratinocytes. The dermis adds the strength to the skin, since it is made of collagen and other extracellular matrix (ECM) proteins. The dermis also contains a vascular and neural plexus. The vascular plexus