CHAPTER 17 Wound debridement
1. Describe the role of debridement in the wound healing process.
2. List contraindications to debridement.
3. Distinguish between selective and nonselective debridement.
4. Compare and contrast four methods of debridement: autolysis, chemical, mechanical, and sharp.
5. Describe the appropriate use of debridement using wet-to-dry dressings, conservative sharp debridement, and high-pressure wound irrigations.
6. List debridement options for the infected wound.
7. Describe at least five factors to consider when selecting a debridement approach.
8. For each method of debridement, list two advantages, disadvantages, and relevant special considerations.
Definition and purpose
Debridement is the removal of nonviable tissue and foreign matter from a wound and is a naturally occurring event in the wound repair process. During the inflammatory phase, neutrophils and macrophages digest and remove “used” platelets, cellular debris, and avascular injured tissue from the wound area. However, with the accumulation of significant amounts of damaged tissue, this natural process becomes overwhelmed and insufficient. Buildup of necrotic tissue then places considerable phagocytic demand on the wound coupled with the continued presence of proinflammatory cells, both of which ultimately retard wound healing (Robson, 1997; Stotts and Hunt 1997). Consequently, debridement of necrotic tissue is an essential objective of topical therapy and a critical component of optimal wound management. Debridement not only is an integral component of wound bed preparation, it also facilitates bacterial balance and moisture balance (Hopf et al, 2006; Robson et al, 2006; Steed et al, 2006; Whitney et al, 2006).
Debridement is believed to achieve several objectives:
1. Reduce the bioburden of the wound. Because devitalized tissue supports the growth of bacteria, the presence of necrotic tissue places the patient at risk for wound infection and sepsis. Using external measures to remove the necrotic tissue and foreign matter reduces the volume of pathogenic microbes present in the wound.
2. Control and potentially prevent wound infections, particularly in the deteriorating wound.
3. Facilitate visualization of the wound wall and base. In the presence of necrotic tissue, accurate and thorough assessment of the viable tissue is hampered.
4. At the molecular level, debridement interrupts the cycle of the chronic wound so that protease and cytokine levels more closely approximate those of the acute wound (Schultz et al, 2003).
Necrotic tissue can appear in various forms. Eschar has the firm, dry, leathery appearance of desiccated and compressed tissue layers (see Plate 24). When the tissue is kept moist, the devitalized tissue, called slough, remains soft and may be brown, yellow, or gray in appearance (see Plates 14, 25, 26A, 32). Slough may be adherent to the wound bed and edges, or loosely adherent and stringy (see Plate 25). Components of slough include fibrin, bacteria, intact leukocytes, cell debris, serous exudate, and significant quantities of deoxyribonucleic acid (DNA) (Thomas, 1990). Once the eschar is removed, slough is often visible covering the wound bed. Maintaining a moist wound environment is essential because continued exposure to air dehydrates slough, causing it to return to a hard, leathery state.
Debridement is indicated for any wound, acute or chronic, when necrotic tissue (which may be slough or eschar) or foreign bodies are present. It is also indicated when the wound is infected. Once the wound bed is clean and viable tissue is present, debridement is no longer indicated. Dry, stable (i.e., noninfected or nonfluctuant) ischemic wounds or those with dry gangrene should not be debrided until perfusion to the extremity has improved (Hopf et al, 2006; Robson et al, 2006; Steed et al, 2006; Whitney et al, 2006). Measurement of vascular status, including an ankle-brachial index, is an important component of the assessment process when considering debridement in a patient with lower leg ulceration. Debridement is also contraindicated for stable eschar covered heels. Treatment goals should be consistent with the goals and lifestyle of the individual (Hopf et al, 2006; Robson et al, 2006; Steed et al, 2006; Whitney et al, 2006).
Methods of debridement
TABLE 17-1 Selective Versus Nonselective Debridement Methods
Selective | Nonselective |
---|---|
Autolysis Enzyme Conservative sharp debridement Biosurgical (maggot) Ultrasonic mist | Surgical Hydrotherapy Wet-to-dry gauze Surgical sharp |
Autolysis
Autolysis as a natural, highly selective painless method of debridement. Specifically, autolysis is the lysis of necrotic tissue by the body’s white blood cells and natural enzymes, which enter the wound site during the normal inflammatory process. The body’s proteolytic, fibrinolytic, and collagenolytic enzymes are released to digest the devitalized tissue present in the wound while leaving the healthy tissue intact (Rodeheaver et al, 1994). As a naturally occurring physiologic process, autolysis is stimulated by a moist, vascular environment with adequate leukocyte function and neutrophil count. Therefore, autolysis is contraindicated in patients with compromised immunity. Autolysis as a sole method of debridement is not recommended for actively infected wounds or wounds with extensive necrotic tissue or significant tunneling and undermining (NPUAP-EPUAP, 2009).
Clinicians, patients, and family members unfamiliar with the process of autolysis can misinterpret the collection of wound exudate and the accompanying odor as indicative of an infection. It is important to emphasize that the wound exudate contains enzymes and growth factors that are essential to wound repair. In fact, wounds treated with moisture-retentive dressings are less likely to become infected than are wounds treated with conventional dressings because semiocclusive dressings are impermeable to exogenous bacteria. In addition, viable neutrophils and other natural substances in wound fluid inhibit bacterial growth (Hutchinson, 1989; Lawrence, 1994).
Debridement by autolysis compares favorably with other methods of debridement in terms of effectiveness (Konig et al, 2005). However, the process is slower than alternative methods such as mechanical and sharp. A multicenter randomized trial conducted by Burgos et al (2000) showed no significant difference in healing of Stage III pressure ulcers with the use of a hydrocolloid for autolysis compared to a commercially prepared topical enzyme product. Another randomized study comparing the same products found the enzyme to be a faster when used to treat Stage IV pressure ulcers on the heel after surgical debridement (Müller et al, 2001). The time frame for the occurrence of autolysis varies depending on the size of the wound and the amount and type of necrotic tissue. Generally, the softening and separating of necrotic tissue is observed within days. If tissue autolysis is not apparent in 1 to 2 weeks, another debridement method should be used (Hopf et al, 2006; Robson et al, 2006; Steed et al, 2006; Whitney et al, 2006).
Chemical
Necrotic wound tissue can be removed through a chemical process using enzymes and sodium hypochlorite (Dakin’s solution). Silver nitrate is another method of chemical debridement; however, it is more commonly used on epibole (closed or rolled wound edges) as described in Chapter 4 and shown in Plate 4 and hypergranulation (see Chapter 6 and Plate 27).
Enzymes.
Similar to autolysis, enzymatic debridement is slower than mechanical or sharp debridement but is frequently used for initial debridement when anticoagulant therapy renders surgical debridement unfeasible (Konig et al, 2005; Ramundo and Gray, 2008). The length of time required to achieve debridement may range from several days to weeks. Unlike autolysis, enzymes may also be used to debride a wound with significant bacterial bioburden or infection (Ramundo and Gray, 2008).
When collagenase is used on a wound with intact eschar, the eschar must be cross-hatched to allow penetration of the enzyme, and the wound surface must be kept moist. Cross-hatching the eschar is achieved by using a no. 10 blade to make several shallow slits in the eschar without damaging the viable wound base. Once the eschar begins to separate or demarcate from the surrounding skin, the enzyme can be applied to the wound edges along the line of demarcation to hasten separation. At this point, conservative sharp debridement can be used to remove softened necrotic tissue. Enzyme treatment can then be continued, or another debridement technique such as autolysis can be instituted. Because these enzymes are selective, damage to viable tissue in the wound bed should not occur if the dressing is continued once debridement is completed and viable tissue is exposed. However, enzyme application typically is discontinued when the wound bed is free of necrotic tissue. More appropriate dressings are available at a fraction of the cost and should be implemented once the wound is debrided. A transient stinging or burning sensation, particularly when the enzyme comes into contact with intact skin, has been reported (Ramundo and Gray, 2008). Barrier ointments can be used to protect the periwound skin.
Dakin’s solution.
Originally used as a topical disinfectant for wounds sustained in war, Dakin’s solution (diluted sodium hypochlorite solution) has a long history of being used to cleanse, debride, and control odor in wounds (Lindfors, 2004). As a debriding agent, Dakin’s solution denatures protein, therefore loosening slough and rendering it more easily removed from the wound. Collagen degradation and fibroblast migration are affected by the concentration of Dakin’s solution. Vick et al (2009) found that less than 0.5% concentration resulted in little or no collagen degradation, whereas 0.5% either partially or completely degraded collagen.
Biosurgical (maggots)
It is theorized that larvae secrete proteolytic enzymes, including collagenase, allantoin, and other agents, which rapidly break down necrotic tissue (NPUAP-EPUAP, 2009). It is also believed that the larvae ingest microorganisms, which are then destroyed. Some researchers are investigating the effects of maggots on fibroblasts and extracellular matrix interaction and enhancement of healing beyond the debridement effects (Chambers et al, 2003; Horobin et al, 2003). Because of this reported action and the emergence of resistant organisms, there is renewed interest in maggot therapy in some centers, and more research supporting this therapy is available (Sherman 2002, 2003; Wallina et al, 2002; Wolff and Hansson, 2003).
Care should be taken to prevent the larvae from coming in contact with healthy skin because the proteolytic enzymes can cause damage. Pain and bleeding have been reported, so the patient should be monitored for both, particularly with the widespread use of antiplatelet therapy (Steenvorde and van Doorn, 2008; Steenvorde et al, 2005). The main disadvantage to maggot therapy is the sensation of crawling that some patients experience, but confinement of the larvae to the wound bed decreases this sensation. Various dressings have been described; most involve periwound protection with mesh or nylon net to contain the larvae and an absorbent pad to absorb exudate (Van Veen, 2008). Biosurgical therapy should not be used with wounds that are poorly perfused, require frequent inspection, or have exposed blood vessels, necrotic bone, or limb-threatening infections (NPUAP-EPUAP, 2009).