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Tissue Non-Viable or Deficient


Non-viable tissue is collectively termed “necrotic tissue ”or “slough”. Necrotic tissue may appear black or brown. When necrotic tissue is yellow and fibrinous, it is often called slough. When the tissue dries out and forms a thick, leathery texture, it is called “eschar.”


“Necrotic burden” is a term used to describe necrotic material, non-viable tissue, exudates, and high levels of bacteria. Necrotic burden tends to continually accumulate in chronic wounds, because such wounds generally result from underlying and uncorrected pathogenic abnormality, such as diabetes mellitus or venous insufficiency. It is often impossible to fully resolve these systemic problems. Therefore, in such cases, wound bed preparation is even more crucial to help facilitate wound closure.


What is debridement, and why is it important?

Debridement is the removal of dead (necrotic), devitalised or contaminated tissue and foreign material from a wound. It is an important initial step in wound bed preparation. The removal of necrotic tissue by debridement is important for a number of reasons. First, devitalised tissue in the wound bed will reduce the clinician's ability to adequately assess the depth of the wound or the condition of the surrounding tissue. Concealed dead spaces could harbour bacteria and increase the risk of local infection. Secondly, necrotic tissue may also mask signs of local wound infection. Finally, the presence of necrotic tissue is a physical barrier to healing, and it supports bacterial growth. Bacterial colonies can produce damaging proteases, which can break down important constituents of the extracellular matrix and inhibit the formation of granulation tissue and re-epithelialisation. Therefore, in addition to removing cell debris, debridement reduces wound contamination and tissue destruction.


Types of debridement

There are five common methods of debridement: surgical or sharp, enzymatic, autolytic, biological or larval and mechanical. Several factors can influence the choice of debridement method used, including the size, position and type of wound; moisture levels; pain management; time available for debridement; the type of healthcare setting and the level of skill of the healthcare professional. In some cases, the use of more than one debridement method may 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 an extensive amount of necrotic tissue is present, which is often the case when the depth of the wound cannot be judged or when there is widespread infection requiring bone and infected material to be removed. As well as being efficient, surgical debridement causes minimal damage to surrounding tissue, and the minor bleeding that follows the procedure can release inflammatory mediators, such as cytokines, that can assist the wound repair process. However, surgical debridement does have limitations. It cannot be used for patients with bleeding disorders or who are immunocompromised. The procedure may be painful, and it may cause transient bacteria and damage to nerves and tendons.


Enzymatic debridement
Enzymatic debridement is the most selective method of debridement, enzymatic debridement uses manufactured proteolytic enzymes to remove necrotic tissue and cell debris from the wound. When these exogenous enzymes are applied directly to the wound surface, they work with naturally occurring enzymes to degrade necrotic tissue. One of the oldest types of enzymatic debriding agents, used for more than half a century, comprises a combination of papain and urea. Papain-urea provides aggressive debridement by first degrading the surface necrotic tissue and then debriding from the surface of the wound down. Some enzymatic debriding agents may cause minor transitory discomfort. In other countries Collagenase which is derived from collagen is used as an ingredient in enzymatic debriding preparations.


Autolytic debridement

Autolytic debridement is a process that occurs naturally, to some extent, in all wounds. Phagocytic cells (such as macrophages) and proteolytic enzymes in the wound bed liquefy and separate necrotic tissue from healthy tissue. Wound dressings, which maintain a moist wound bed, can provide an optimal environment for autolytic debridement. Autolytic debridement can result in significant wound fluid, which should be considered when selecting an appropriate dressing. Autolytic debridement requires limited technical skill, and does not damage healthy tissue surrounding the wound. Furthermore, the patient experiences minimal pain with this method.


Biological or larval therapy
Myiasis the use of larvae or maggot therapy as it is more commonly known has recently undergone a revival due to factors including increased antibiotic resistance and the ability to commercially breed sterile flies. The larvae or maggots only digest necrotic tissue, slough and bacteria, leaving a clean wound bed. Larval therapy eradicates infection and odour.


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. These dressings cause separation of necrotic tissue from the wound bed when the dressing is removed. This can cause the patient significant discomfort and pain and damage newly formed tissue. Wound irrigation uses a pressurised stream of normal saline. High-pressure irrigation removes bacteria and necrotic debris from wounds but can also drive bacteria into soft tissue. Whirlpool therapy is another form of powered irrigation that loosens and removes necrotic tissue, debris and exudate. Wound irrigation is not suitable for wounds that have fragile granulation tissue.


Maintenance debridement:

An extended phase of debridement may be more appropriate than a single intervention. Until recently, debridement, regardless of the method used, has been thought of as a single treatment. While a single episode of debridement may be appropriate for acute wounds, chronic wounds require more frequent debridement because of the accumulating necrotic burden resulting from underlying pathogenic conditions. Therefore, continuous removal of the necrotic burden is an important part of wound bed preparation. For these reasons, when treating chronic wounds, debridement should be viewed as an on-going process rather than as a single intervention. Maintenance debridement, will offer distinct advantages in wound management, because autolytic and enzymatic debridement are more selective and generally less painful for the patient, they are therefore the recommended methods of treatment when extended periods of debridement are required.