Preparing the Wound Bed – Debridement, Bacterial Balance, and ...

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Speed Tissue selectivity Painful wound Exudate Infection Cost TABLE 3 KEY FACTORS IN DECIDING METHOD OF DEBRIDEMENT ostasis are available. Removal of devitalized tissue may only be performed by trained healthcare professionals in approved care settings. Autolytic debridement. Moist interactive dressings – especially hydrogels, hydrocolloids, transparent films, and alginates – can provide autolytic debridement. These dressings create an environment capable of liquifying slough and promoting granulation tissue at the same time. 22,23 If tissue autolysis is not apparent in 24 to 72 hours, another form of debridement should be used. The eschar surface can be scored with a scalpal blade, making superficial parallel grooves on the hard eschar surface in a grid pattern. The grooves are not intended to penetrate viable tissue, and bleeding should be minimal or absent. Enzymatic debridement. The most selective mode of debridement – enzymatic debridement – relies on naturally occurring enzymes applied exogenously to the wound surface to degrade debris. In Canada, the only licensed enzymatic product is collagenase, isolated from Clostridium histolyticum. Collagenase exists in wounds naturally as a matrix metalloproteinase, where it has been shown to degrade immature collagen in the wound matrix. Early debridement is promoted because collagenase acts as the rate-determining enzyme in collagen degradation, catalyzing cleavage of glycine in the native collagen triple helix. It is highly specific for collagen and is thought to promote debridement by digesting collagen bundles that bind nonviable tissue to the wound bed. Some small trials report faster debridement with collagenase compared to placebo. 24,25 Future trials are needed to confirm if this agent has a role promoting later stages to stimulate granulation tissue and re-epithelialization. 26 22 OstomyWound Management Surgical Enzymatic Autolytic Mechanical 1* 2 4 1 1 4 * 1 is usually most desirable, and 4 is usually least desirable. 2 1 2 4 3 2 4 3 1 3 4 1 3 4 3 2 2 3 Collagenase is inactivated by heavy metals (silver, zinc) and detergents. In the Unites States, papain and papain-urea products are also available. 27 Enzymatic debridement appears to be most useful in the removal of eschar from large wounds when surgical techniques cannot be utilized. Debridement can be facilitated by cross-hatching or scoring hard eschar prior to application of the enzyme. Problems arising from enzymatic debridement relate to the production of excessive amounts of exudate with these agents, local irritation to surrounding skin, and possible infection. Mechanical debridement. Mechanical debridement physically removes debris from the wound. It may be used in the management of surgical wounds along with pressure, ischemic, and venous leg ulcers. The simplest form of mechanical debridement is wet-to-dry gauze, but this technique is nursing time-intensive and costly. This often causes bleeding and pain with removal, leading to nonselective trauma to the wound. Other methods include irrigation, pulsatile lavage, and whirlpool therapy. 27,28 In the whirlpool or other foot-soaking procedures, the entire foot is immersed, causing the maceration and bacterial seeding (bacterial soup) of susceptible areas such as the toe webs, nail folds, and tiny cracks in the skin (fissures). (See Recommendation 9 of Best Practices for the Prevention and Treatment of Pressure Ulcers by Dolynchuk et al on page 46.) TABLE 4 CONTRAINDICATIONS FOR SURGICAL DEBRIDEMENT OF VIABLE TISSUE Absolute Contraindications • Lack of expertise in procedure • Nonhealable ulcer (ie, insufficient vascular supply to allow healing) • Septicemia in the absence of systemic antibacterial coverage • Medically unfit patient Relative Contraindications • Patient on anticoagulants (dependent on INR [international normal ratio]/PTT [activated partial prothrombin time] etc.) • Home care setting
Recommendation 6 Assess the Wound for Bacterial Balance and Infection The presence of wound-associated bacteria alone does not indicate infection or impaired wound healing. Indeed, some authors have suggested that a small amount of a certain bacteria species in a chronic wound facilitates healing. 29,30 In clinical practice, assessing when a wound has moved from a symbiotic bacterial load that does not cause tissue damage to an increased bioburden causing impairment of wound healing can be difficult. The following equation demonstrates that although bacterial quantity and virulence are significant in assessing a wound for infection, host factors are of overriding importance. Risk of wound infection 31 = Bacterial dose x virulence Host resistance Factors such as immunosuppression, diabetes, and medication all can influence whether any bacteria present will impair wound healing. Furthermore, these factors can act to mask classical signs of infection such as erythema, increased temperature, pain, and edema. Swab technique is important to obtain meaningful results. 32 The wound should be cleansed with saline or water and all debris should be removed. The healthy appearing granulation is swabbed in a zigzag pattern, gently rotating the tip of the swab (swabs are only recommended if clinically indicated). If the wound is relatively dry, the swab may be moistened with the transport media prior to swabbing. A semiquantitative swab is then inoculated on standard media in the lab and streaked in four quadrants. Results will indicate no growth to 1 to 4+ growth of an organism, depending on the number of streaked quadrants that support bacterial growth. These swabs are quick and inexpensive. The semiquantitative swab correlates well to the gold standard quantitative biopsy results, 33 but there is some loss of specificity. Despite the fact this is the procedure of choice in most centers, inadequate wound bed preparation will result in an excess number of confusing, nonsignificant wound surface colonies appearing on the agar plates in the lab. The clinical assessment of wound bioburden and the choice and route of antibacterial agents should be based on host and wound factors in association with wound swab results. The concepts of bacterial contamination, colonization, critical colonization, and local and systemic infection lend themselves to guidance with regard to when to use antimicrobial agents in wound care (see Table 5). Most wounds are contaminated and contain nonreplicat- 24 OstomyWound Management ing organisms. Colonization occurs when organisms are replicating but not causing host injury. Skin commensals such as Staphylococcus epidermidis and Corynebacterium species are the most common colonizers. Neither contaminated nor colonized wounds show signs of infection, and impairment of wound healing is unlikely. The concept of critical colonization (increased bacterial burden) has recently been introduced to describe wounds moving between the spectrums of colonization (where the host is unaffected) and local infection (in which host injury occurs). It has been suggested that during critical colonization, subtle clinical signs of infection such as increasing pain/tenderness, increasing serous exudate and friable granulation tissue, or failure to heal may be present prior to the classical signs of foul odor, frank pus, surrounding erythema, increased temperature, pain, and swelling associated with infection. 34 It is important to emphasize that many people with chronic wounds, in particular people with diabetes, have an impaired host response. These patients may therefore exhibit only subtle signs, or even have a complete absence of signs of infection (ie, no elevation in temperature) when bacteria are damaging the skin and delaying healing. 35 A semiquantitative swab with 4+ growth of a significant pathogen or a quantitative biopsy with ≥ 1.0 x 10 6 cfu/g (cfu = colony forming unit) of tissue in the presence of nonhealing may be an indication for systemic antibacterial therapy. Therefore, host monitoring is a vital part of assessment, with factors such as raised blood sugar levels in people with diabetes often being a helpful indicator of local or systemic infection. Recommendation 7 Cleanse Wounds with Normal Saline or Water. The Use of Topical Antiseptics Should be Reserved for Wounds that are Nonhealable or the Local Bacterial Burden is a Greater Concern than the Stimulation of Healing Cleansing and irrigation are used to eliminate exudate and surface debris from wounds. Not only does this process facilitate healing, but it also decreases bacterial burden by removing heavily contaminated surface slough and debris. Saline or sterile water are agents of choice for most wounds. Tap water should not be used for immunosuppressed patients and the water source should be reliably clean before advocating it as treatment in other chronic wounds. 36 Rodeheaver 28 studied wound cleansers in vitro to assess cellular toxicity. He concluded that nonionic agents are best,
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