Management of Tissue necrosis

 

Debridement is the removal of dead, non-viable/devitalised tissue , infected or foreign material from the wound bed and surrounding skin.Debridement should be considered an integral part of the process of caring for a patient with a wound. at a most basic level, debridement is defined as a natural process that occurs in all wounds and facilitates the removal of damaged and necrotic tissue, extraneous debris and bacteria from the wound to encourage the formation of healthy granulation tissue.

Wound terminology

Necrotic Wound

Necrotic wounds are localized defects or excavation of the skin or underlying soft tissue that contains dead, avascular tissue.

  Eschar

An eschar is a hardened dry crust of necrotic tissue that may form over a wound. It is usually thick, leathery, and black. A white eschar indicates total ischemia (deficiency of blood) of the tissue. A red (or brown) eschar indicates  hemoglobin from destroyed red blood cells Black white and Brown eschar

Scab

A scab is a collection of dried blood and serum over a wound which has formed during the wound healing process. It is a combination of platelets, red blood cells, white blood cells, fibrin, and plasma. As the combination dries out, the scabs usually take on a deep, rusty brown color and develop crusty edges. Scabs generally remain firmly in place until the skin underneath is repaired and new skin cells appear.  Scabs actually prevent new skin cells from forming, which can result in longer healing time. Preventing scabs is the best way to promote healing. However, removing scabs is also dangerous since scabs function as protective caps over the wound and prevent dirt, germs, and other contaminants from entering the wound bed. In addition, if scabs are prematurely removed, the revealed skin could be red and oozing. New scabs may reform, but often, the new skin develops scar tissue.  A white scab is usually caused by moisture within the scab. The normal red-brown color of a scab changes when it is exposed to water from a bath or shower.

Crust

Crust means any hard outer portion or surface area of solid matter. When a wound is described, a crust is used as a generic term describing an eschar and a scab. Generally, however, a crust over a wound is called a scab.

Slough

A slough is a layer or mass of dead tissue separated from the surrounding living tissue in a wound.

Callus  (Callosity)

A callus is an especially toughened area of the skin which has become relatively thick and hard in response to repeated friction, pressure, or other irritations

Scale

A scale is a thin piece of keratin layer of the skin that is produced because of abnormal skin conditions, most frequently excessive dryness.

Non-viable material and debris in a wound can:

■  Pose a physical barrier to healing  and may impede normal extracellular matrix formation, angiogenesis, granulation and epidermal resurfacing.

■  Reduce the effectiveness of topical preparations, such as antimicrobials and pain relief.

■ Mask or mimic signs of infection  and serve as a source of nutrients for bacteria, particularly anaerobes such as Bacteroides species and Clostridium perfringens.

■ Contribute to overproduction of infammatory cytokines, which can promote a septic response and lead to the overproduction of matrix metalloproteinases (MMPs)

■  Prevent the practitioner from gaining an accurate picture of tissue destruction and inhibit correct assessment of the wound, which is particularly relevant in pressure ulcers and diabetic foot ulcers

■  Lead to overproduction of exudate and odour.

Debridement is thought to further support wound healing by

  • Stimulating a response to prevent infection
  • Reducing infl ammatory cytokines, fi bronectin, and metalloproteinases produced from chronic inflammation due to the presence of necrotic tissue
  • Promoting DNA synthesis and keratinocyte growth, both of which are inhibited by products of the inflammatory response
  • Converting the chronic nonhealing wound physiology to that of an acute wound

 

Clinical practice guidelines recommend initial debridement to remove the obvious necrotic tissue and maintenance debridement to maintain readiness of the chronic wound bed for healing. There is growing opinion that an initial aggressive surgical debridement may obviate the need for future multiple debridements. At present, most experts recommend an excisional debridement at the time of presentation. This entails removal of all nonviable tissue and a margin of normal skin. This may be critical as the edge (e.g., the 2–3-mm rim of the wound) of chronic wounds has been shown to exhibit distinct pathogenic changes (e.g., hyperproliferative/hyperkeratotic epidermis, dermal fi  brosis, increased procollagen synthesis), and fibroblasts exhibit senescence and impaired migration.

Thereafter, maintenance debridement involves removing unhealthy tissue, slough, and bacterial biofilm that builds up on the wound.

 

Type Mechanisms of action Advantages Disadvantages
Autolytic A naturally occurring process in which the body’s own enzymes and moisture rehydrate, soften and liquify hard eschar and slough. Occlusive or semi-occlusive dressings (hydrogel,hydrocolloid, alginate or Hydrofber) help to achieve moisture balance, by absorbing excess exudate or donating moisture Can be used before or between other methods of  ebridement (eg a hydrogel could be  appliedto soften tissue before larval therapy), when there is a small amount of non-viable tissue in the wound, ie maintenance debridement The process is slow, increasing potential for infection and maceration
Mechanical Traditional wet-to-dry method is not recommended. Newer methods include removing non-viable tissue from a wound using a monoflament soft pad (Debrisoft®, Activa Healthcare) UCS™ DEBRIDEMENT Using Debrisoft® or UCS™ DEBRIDEMENT can be more selective, quick and easy. It can achieve effective removal of hyperkeratosis. Little pain is experienced. Patients can use it undersupervision Not suitable for use on hard, dry eschar.

Can be used as a precursor or follow-upto larval therapy or sharp debridement.

Not suitable for already painful wounds.

Ultrasonic Devices deliver ultrasound either in direct contact with the woundbed or via an atomised solution

(MIST®; Celleration). Most include a built-in irrigation system and are supplied with a variety of probes for different wound types

Immediate and selective. Can be used for excisional debridement and/or maintenance debridement over several sessions. Has some antimicrobial activity Availability limited due to higher costs and requirement for specialist equipment. Requires longer set-up and clean-up time (involving sterilisation of hand pieces) than sharp debridement.

May require multiple treatments

Hydrosurgical Removal of dead tissue using a high energy saline beam as a cutting implement Short treatment time and selective. Capable of removing most, if not all, devitalised tissue from the wound bed without compromising healthy tissue. Can also remove hyperkeratotic tissue from wound margins Requires specialist equipment and training. Potential for aerosol spread of infection. Can be painful. Not always available and associated with higher costs, although is often cost-effective when compared with surgical debridement, since it does not require theatre time.
Sharp Removal of dead or devitalised tissue using a scalpel, scissors and/or forceps to just above the viable tissue level. Undertaken in conjunction with other therapies (eg autolytic debridement). The most commonly used form of debridement in managing the diabetic foot. Selective and quick.

No analgesia normally

required. Works best on

harder eschar that can be

grasped with forceps

Practitioners must be able to distinguish tissue types and understand anatomy as procedure carries risk of damage to blood vessels, nerves and tendons. Not as effective on soft adherent slough.

Does not result in total debridement of all non-viable tissue

Surgical Excision or wider resection of non-viable tissue, including the removal of healthy tissue from the wound margins, until a healthy bleeding wound bed is achieved. Selective and best used on large areas where rapid removal is required It can be painful for the patient and anaesthetic is normally required.

Associated with higher costs related to theatre time

Autolytic debridement

This natural process is known as autolytic debridement and is considered the safest way to debride. It is the method most usually undertaken by nurses without specialist debridement skills or equipment, using appropriate moist wound dressings. Autolytic debridement can be slow and is not always the most benefcial treatment for progressing a wound towards healing . If the process of debridement is accelerated, healing may be achieved more quickly.

Dressings that optimise a moist wound environment, by adding (hydrating wound eschar) or removing moisture (excess exudate), will facilitate autolytic debridement of the wound bed. other more active forms of debridement may be needed to accelerate and optimise wound healing.

Mechanical debridement

Wet-to-dry debridement

One technique used to achieve mechanical debridement is the wet-to-dry method. A moist  gauze pad is applied to the wound. As the devitalised tissue dries, it rehardens and becomes attached to the gauze; when the dressing is removed, the adhered material is pulled free.  The wet-to dry debridement method often results in a lack of procedural concordance, with an increased risk of infection; also, the gauze remnants can potentially act as foreign bodies within the wound bed. The disadvantages of this method are described as injury to normal tissue and pain, along with the necessity for  frequent dressing changes. In addition, while cost of the gauze is low, application is said to be time  consuming and costly.

Monoflament fibre pad

The monoflament fbre product has recently been introduced as a modern, wound-debriding product, designed to mechanically remove slough and devitalised cells from the wound bed. Case studies suggest that slough, hyperceratotic debris and crusts of desiccated exudate are bound in the fbre composite and thereby removed from the wound and surrounding skin.The wound-contact side is feecy in appearance and, once wetted, is gently wiped over the surface of the wound for 2-4 minutes.The monoflament fbre pad has been used in debriding a variety of wound types, including venous leg ulcers, diabetic foot ulcers (neuropathic and neuro-ischaemic) arterial ulcers  mixed aetiology ulcers , pressure ulcers  and traumatic wounds.

 

Enzymatic dressings

For a few hundreds of years, patients with chronic wounds have been treated topically with proteolytic enzymes for example in the form of fruit juices.  Enzymatic debridement is a specifc wound debridement option using proteolytic enzymes in gels or ointments  which should work synergistically with endogenous enzymes.

Enzymatic debridement can be useful in patients with wounds where mechanical debridement options are not available or are contraindicated, for example  in patients with  bleeding problems using debridement, proteolytic enzymes are used to hydrolyse peptide bonds, in order to facilitate the  removal of non-viable tissue from a wound. These enzymes can be divided in exo and endopeptidases.  Exopeptidases hydrolyse the amino or carboxy terminal protein, whereas endopeptidases degrade peptide bonds within the protein molecules.

Matrix metalloproteases (MMPs) are zinc-dependent endopeptidases , with a subgroup of metalloenzymes called collagenases. Humans generate endogenous collagenases to facilitate the physiological balance between the assembly and degradation of collagen.Collagenases are the only endoproteases that can degrade human triple helical collagen, but do not  attack keratin  fat, fibrin or haemoglobin. Necrotic tissue consists of cellular debris embedded in an extracellular matrix (ECM), mainly consisting of type IV collagen, glycoproteins and proteoglycans. These components are released by the activity of collagenases and can subsequently be degraded by macrophages and other proteases. The resulting collagen fragments stimulate additional fbroblasts and macrophages and thus induce chemotactic effects. Streptodornase is a deoxyribonuclease (DNAse) with endonucleolytic activity against double-stranded DNA. Streptodornase will contribute a complex with free plasminogen, which catalyses the conversion of plasminogen to plasmin. It liquefes the viscous nucleoprotein of dead cells or pus and has no effect on living cells. Similarly, coagulated blood can be liquefed and then be absorbed. By these characteristics, the streptodornase is particularly suitable when used in combination with other enzymes.

Papain digests necrotic tissue by liquefying fbrinous debris across a wide range of pH, from 3 to 12. For its full activity, it requires the presence of sulphydryl groups, such as cysteine. Usually, urea is combined with papain. Urea also denatures proteins, making them more susceptible to proteolysis by papain and exposes the necessary activators for papain in necrotic tissue.

To ensure the full effectiveness during the therapy with proteolytic enzymes, the wounds must always have sufficient moisture in the environment .Application of the enzymatic ointment should be performed in a coating of thickness about 2–3mm on the non-viable tissue areas, once or twice daily. It is important to respect the fact that enzymes need a moist environment to be effective. Therefore, dry wounds are a relative contraindication for the use of proteolytic enzymes. The additional use of, for example, antiseptics or soaps should be avoided, as some of the enzymes become ineffective in the presence  of these solutions. Products with proteolytic enzymes can lead to irritation of the peri-wound skin, with clinical signs of infammation or discomfort. This, in particular, is most important when using papain, as considerable pain induced by infammatory response has been commonly described. Therapy with streptodornase can cause fever, chills, and leucocytosis, due to the absorption of split purines and pyrimidines. Streptokinase and streptodornase are effective as antigens and thus the formation of antibodies may result. In some cases, clinically-relevant contact sensitisation, with allergic contact dermatitis, has been reported.

Honey dressing

It is a viscous, supersaturated, sugar solution, containing approximately 30% glucose, 40% fructose, 5% sucrose and 20% water, as well as many other substances, such as amino acids, vitamins, minerals and enzymes. Honey has been used to treat a wide range of wound types with necrotic tissue or slough. Other  indications are wound infections, even when they are caused by, for example, Pseudomonas aeruginosa or meticillin-resistant Staphylococcus aureus (MRSA). Honey osmotically draws fuid from the surrounding tissue. This reduce wound oedema and, along with the increased exudate, results in autolytic debridement. The claimed antimicrobial effectiveness of honey may be partly explained by an osmotic dehydration, a low pH-value of 3.0–4.5  and the release of small amounts of hydrogen peroxide or methylglyoxal. It is claimed that honey has anti-infammatory properties and also stimulates immune responses.  Although the exact mode of action remains unclear, it has been observed that reactive oxygen species production is decreased and TNF-α release is enhanced by honey. In addition to the suggested autolytic debridement effects of honey, it is also used because of the claimed antibacterial activities and ability to deodorise wounds.

Jet lavage/hydrosurgery

The principle of jet lavage debridement (hydrosurgery) is basically an evolution of the lavage of wounds, used since the ancient times in acute wounds and, more recently, in chronic wounds.

It is related to water irrigation, which can physically remove foreign bodies, debris and  any other kind of loose material from the wound. The more intense and fast the irrigation, the  more intense are the energies transferred to  the tissues and consequently the more extensive the debridement.The gentler options can be used for removal of necrotic debris, slough and bioflms and all other types of material with a loose structure that have a weak consistence and may be removed easily. The more powerful options, especially those using the so called Venturi effect  have the capacity to precisely debride dense fibrotic tissues and materials, and may in some cases be used on bone structures, depending on the velocity and intensity of the jet stream passing through the instrument tip. Another interesting aspect of this technology is the possibility to combine it with antiseptic solutions. This may maximise the antimicrobial activity, which is an important part of the debridement procedure.

The principal limitation of this technology is that it may be painful for some patients and for this reason it should only be used when an adequate pain control can be achieved, such as by use of local anesthesia.Another issue is that jet lavage has been suspected to disseminate bacteria in the environment because of the formation of an aerosol during the application. This may contribute to the contamination of the setting in which the procedure is carried out.

Ultrasound debridement

The most renowned application of ultrasound (US) in medicine is related to the diagnostic-imaging feld, in which they reached a level of sophistication considered the golden standard in many areas of medicine and surgery. However, on the therapeutic side, many applications of ultrasound in the range of the megahertz (MHz) have recently been developed. These include surgical cutting and coagulation in laparoscopy or, to the specifc interest of this document, in the debridement of chronic lesions. US can, depending on the frequency and intensity of the mechanical energy transmitted, interfere with many different structures, from inert protein material to cellular bodies, exerting a range of effects that may vary from destruction to dislocation and physical modifcation.Ultrasonic waves are also claimed to lead to destruction of bacteria and disruption of biofilms.

 

Sharp and Sugical debridement.

Surgical and sharp debridement are rapid methods of debridement and have been in use for many years. Sharp debridement is defined as a minor surgical bedside procedure, involving cutting away tissue with a scalpel or scissors.‘Surgical debridement’ is defned as a procedure performed under general anaesthesia, using various surgical instruments. Sharp debridement is an action that may be performed by any kind of medical specialist, including nurses family doctors, dermatologists, podiatrists and other personnel without surgical background.

Wound specific debridement.

Necrotic tissue may be observed in chronic wounds with various etiologic factors.

Arterial/Ischemic Wounds

Necrotic debris in the ischemic wound usually appears as dry gangrene. It may have a thick, dry, or desiccated black/gray. Appearance. It is usually firmly adherent to the wound bed. Dry gangrene is often surrounded by an erythematous halo. Arterial wounds as a rule should not be debrided until revascularization as the surrounding tissue does not have adequate perfusion to support the procedure, resulting in worsening of the wound. In the presence of active infection, the wound should be debrided immediately regardless of the need for revascularization. However, the standard of care for dry gangrene or an arterial wound without clinical signs of infection is revascularization to optimize blood supply to the wound before debridement to ensure potentially viable tissue is not removed unnecessarily. Once blood flow has been reestablished, the wound may be debrided. This can be accomplished by waiting 4 to 8 days after an open bypass or 3 to 4 weeks following endovascular surgery before performing any definitive debridement on a noninfected wound.

Diabetic Neuropathic Ulcers

Neuropathic or neurotrophic wounds usually present with hyperkeratosis surrounding the wound in addition to necrotic tissue. These wounds are most common on the plantar aspect of the foot. This hyperkeratosis appears as callus formation at the wound edge, which should be shaved down to normal-appearing or bleeding skin. It is standard practice in debriding diabetic neuropathic wounds to excise the wound completely on initial presentation, removing a margin of 1 to 2 mm of intact skin. The edges of the wound should be beveled at a 45-degree angle.

Venous Leg Ulcers

Venous leg ulcers can present with blisters, slough or, less commonly, eschar. The wound bed in a majority of chronic venous ulcers becomes covered with a yellow fibrinous  material, slough. Eschar may be attributed to desiccation of the wound and necrotic debris. It is not typically seen when the patient is receiving compression therapy.

Pressure Ulcers

Necrotic debris that occurs in pressure ulcers is directly related to the degree of tissue destruction. In the early stage of pressure sore formation, the tissue may appear firm and hard (indurated), with a purple or black discoloration on intact skin. This is indicative of the death of tissues between the skin and an underlying bony prominence. The overlying skin appears purple in color, called deep tissue injury. In time, the skin may die and an eschar appears, a phenomenon referred to as demarcation. In most cases, it takes 3 to 7 days for the wound to fully demarcate. The firm, black eschar represents full-thickness destruction of the skin and often the subcutaneous tissues.

Cells and Bacterial Biofilms

Senescent nonfunctional cells generally occur on the periphery of the wound, at the rim or wound edge. Typically they extend 2 to 3 mm from the edge of the wound. In diabetic foot ulcers, the 1 to 2 mm at the edge of the wound contains senescent nonfunctional cells and contributes to the hyperkeratotic tissue observed in these wounds.

Biofilms develop on the base of chronic wounds. A bacterial biofi lm is a polymicrobial sessile community of microorganisms that develop on the surface of chronic wounds, not reaching critical colonization levels and thus, not causing classic wound infection. The biofilm is an effective barrier to topical dressings and antimicrobial therapy and as such inhibits healing. Bacterial biofilms have been shown to be present.

OUTCOME MEASURES

There are three characteristics for evaluating the effectiveness of debridement: the type of necrotic tissue, the amount of necrotic tissue, and the adherence of necrotic tissue to the wound bed.

Necrotic Tissue Levels

The quantity of necrotic tissue in the wound bed should diminish progressively with appropriate therapy. The amount of necrotic tissue can be measured in several ways: by linear measurements (measuring the length and width of the necrotic debris), visual assessment of the percentage of the wound bed covered with nonviable tissue, digital planimetry (measuring the area of the wound using photographic analysis), and photography.

A rating scale similar to the following may be used:

1 = None visible

2 = <25% of wound bed covered

3 = 25%–50% of wound covered

4 = >50% and <75% of wound covered

5 = 75%–100% of wound covered

Type of Necrotic Tissue

When conservative methods of debridement are used, including mechanical, autolytic, and enzymatic techniques, the type of necrotic tissue should change as the wound improves. As the necrotic tissue is rehydrated, the appearance will change from a dry, desiccated eschar to soft slough and, fi  nally, to a loose tissue that does not adhere to the wound bed. The color usually changes as well, the black/brown eschar giving way to yellow or tan slough. Rate the type of necrotic tissue by using a scale similar to the following:

1 = None visible

2 =  White/gray nonviable tissue and/or nonadherent yellow slough

3 = Loosely adherent yellow slough

4 = Adherent, soft black eschar

5 = Firmly adherent, hard black eschar

Adherence of Necrotic Tissue.

Adherence of the necrotic tissue should decrease as debridement progresses. Initially, the necrotic tissue may be firmly attached to the wound base as well as the wound edges. As conservative debridement methods proceed, the necrosis begins lifting, loosens from the edges of the wound, and eventually disengages from the base of the wound. Evaluate adherence using a rating scale similar to that for types of necrotic tissue.