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Wound Bed Preparation

A Clinical Concept led by Smith & Nephew

Debridement

What is debridement?

Debridement involves the removal of dead, devitalized or contaminated tissue and foreign material from a wound, and is an important initial step in wound bed preparation. Non-viable tissue is collectively termed necrotic tissue or slough. Necrotic material may appear as black or brown colored tissue. Where necrotic tissue is yellow and fibrinous it is often termed slough. When the tissue dries out and forms a thick and leathery texture, it is referred to as eschar.


Why does necrotic tissue accumulate in chronic wounds?

'Necrotic burden' is a term used to encompass necrotic material, non-viable tissue, exudate and high levels of bacteria. Necrotic burden tends to continually accumulate in a chronic wound since this type of wound is generally a result of an underlying and uncorrected pathogenic abnormality, such as diabetes or venous insufficiency. Often it is not possible to fully resolve these systemic problems, which makes effective wound bed preparation even more crucial to help facilitate wound closure.


Why is debridement important?

The removal of necrotic tissue by debridement is of great importance for a number of reasons. First, devitalized tissue in the wound bed will reduce the ability of the clinician to adequately assess the depth of the wound or the condition of the surrounding tissue. Concealed dead spaces could harbor bacteria and increase the risk of local infection. Secondly, necrotic tissue may also mask signs of local wound infection. Lastly, the presence of necrotic tissue is a physical barrier to healing and supports significant bacterial growth. Bacterial colonies, which are often present in necrotic tissue, can produce damaging proteases, which break down important constituents of the extracellular matrix and have a negative effect on the formation of granulation tissue and reepithelialization. Therefore, the process of debridement reduces wound contamination as well as removing cell debris thereby reducing tissue destruction.


Types of Debridement

There are four methods of debridement; sharp or surgical, enzymatic, autolytic and mechanical. Once the clinician has made the decision to debride, several factors can influence the choice of debridement method employed (2, 5). These include the size, position and type of wound, moisture levels, pain management, time available for debridement and healthcare setting. Moreover, in treating chronic wounds, it is important to consider the patient's overall condition when choosing the debridement method. In some cases, the use of more than one debridement method may also be appropriate.


Surgical (or Sharp) Debridement

Surgical or sharp debridement is the fastest way to remove debris and necrotic tissue from the wound bed. Surgical debridement is sometimes performed when there is an extensive amount of necrotic tissue in the wound. This is often the case when the depth of the wound cannot be judged or if there is widespread infection requiring bone and infected material to be removed (8). Other than being an efficient method, surgical debridement causes minimal damage to surrounding tissue, and minor bleeding following the procedure can release inflammatory mediators, such as cytokines, that can assist the wound repair process. Surgical debridement does however, have limitations. It cannot be used for patients with bleeding disorders or who are immunocompromised, The procedure may be painful, cause transient bacteremia and damage to nerves and tendons (9).


Enzymatic Debridement

Enzymatic debridement is the most selective method of debridement employing the use of manufactured proteolytic enzymes. When these are applied directly onto the wound surface, they work together with naturally occurring enzymes to degrade necrotic tissue.


Autolytic Debridement

Autolytic debridement is a process, which to some extent, occurs naturally in all wounds. Phagocytic cells (such as macrophages) and proteolytic enzymes in the wound bed, liquefy and separate necrotic tissue and eschar from healthy tissue. Wound dressings, which maintain a moist wound bed, can provide an optimal environment for debridement, as they allow the phagocytic cells to liquefy necrotic tissue thereby promoting granulation. Unsurprisingly, the process of autolytic debridement can result in significant wound fluid, which should be considered when selecting an appropriate dressing. Autolytic debridement is easy to perform and does not damage healthy tissue surrounding the wound. Furthermore, the pain experienced by the patient when using this method is minimal. As autolytic debridement occurs naturally, the process requires limited technical skill.


INTRASITE Gel and Autolytic Debridement

INTRASITE Gel is an excellent example of an advanced wound care product which facilitates autolytic debridement by re-hydrating hard necrotic tissue. This amorphous hydrogel dressing also loosens and absorbs slough and exudate. Notably, during the later stages of wound closure, it provides an optimum moist wound environment (33). This makes INTRASITE Gel ideal for every stage in the wound management process and of particular importance in wound bed preparation.


Mechanical Debridement

Mechanical debridement is a non-selective method that physically removes debris from the wound. Examples of mechanical debridement include wound irrigation, whirlpool therapy and wet-to-dry dressings. Wet-to-dry dressings are the simplest form of mechanical debridement (34).
These dressings cause mechanical separation of eschar from the wound bed once the dressing is removed. This can, however, cause the patient significant discomfort and damage newly formed tissue (35). Wound irrigation involves the use of a pressurized stream of water High-pressure irrigation removes bacteria and necrotic debris from wounds but could drive bacteria into soft tissue (4). Whirlpool therapy is another form of powered irrigation which loosens and removes necrotic tissue, debris and wound exudate. This is suitable for use in inflammatory wounds but not for those with fragile granulation tissue (36).


Why is an Extended Phase of Debridement ('Maintenance Debridement') More Appropriate than Single Intervention Therapy?

Until recently, debridement, whether it is done by surgical, enzymatic, autolytic or mechanical means, has been thought of as a single therapeutic step within defined time lines, While a single episode of debridement may be appropriate in acute wounds, with chronic wounds it is generally not possible to fully remove the underlying pathogenic abnormalities, therefore the necrotic burden continues to accumulate. It is likely that this accumulation of necrotic burden could, in itself, cause the failure of wound repair. Therefore, an important part of wound bed preparation is the recognition Of a continual removal of the necrotic burden throughout the lifespan of the wound. In treating chronic wounds, debridement should be viewed as an extended, on-going process, rather than a single intervention. In recognizing this, an extended 'maintenance' phase of debridement has been proposed, which will offer distinct advantages in wound management. Since autolytic and enzymatic methods of debridement are more selective and generally less painful to the patient, these methods are recommended over an extended period.