Choosing the optimal wound dressing for irradiated soft tissue wounds

Abstract

This article reviews the healing state of the previously irradiated wound, the tenets for optimal wound care, and the choices of wound dressings now available for its management. The goal in assisting a previously irradiated surgical wound to heal is to transform its chronic wound state into an acute wound state. This transformation encourages wound healing to proceed. Six major moisture-retentive dressing categories exist to optimize its healing. They are classified into the alginates, foams, gauzes, hydrogels, hydrocolloids, and transparent films. Optimal wound care management for previously irradiated wounds involves (1) adequately debriding and cleansing the local wound, (2) accurately assessing the wound, (3) choosing the appropriate dressing based on the wound assessment, and (4) encouraging granulation tissue formation and reepithelialization.

Delayed postoperative wound healing is common in patients who have had previous radiation. This article describes the state of the irradiated wound, the tenets for optimal wound care, and the various categories of wound dressings available for its management.

IRRADIATED WOUNDS

Radiation affects all cells within its treatment field. For adequate healing to occur within a previously irradiated area, specific wound-healing events of hemostasis, inflammation, angiogenesis, collagen synthesis and turnover, epithelialization, and contraction must take place. When any of these steps are impaired, a nonhealing wound results. A delay in earlier phases of healing interferes with all subsequent stages of healing.

Radiation impairs soft tissue healing by 3 major processes: microvasculature obliteration, excessive fibrosis, and the disruption of cellular proliferation. 1 , 2 The radiation effects on vasculature make a major impact for its future wound healing. The influence of irradiation on skin depends on the following variables: the area and volume of tissue irradiated, fractionation, total dose, type of radiation used, and individual skin type. In addition, the time interval between radiation exposure and the observed effects determines whether an early reaction (within several weeks after treatment) or a delayed reaction (months or years after treatment) is apparent. 3 The acute radiation effects to the skin (dry desquamation, hyperpigmentation, and hair loss) are reversible. The late effects on skin (atrophy, scaling, telangiectasia, subcutaneous fibrosis, and necrosis) are irreversible and chronic.

Radiation injury occurring early is caused by the depletion of rapidly dividing cells. Early radiation injury occurs during treatment and several weeks after the completion of radiation. Early injury takes place in rapidly proliferating tissue such as mucosa. Late radiation injury (months to years later) occurs in tissues proliferating slowly or not at all. The late skin effects are a function of the total dose and the fraction size. 4 Patients at risk for dermal complications have poor nutrition or have received a radiation dose greater than 5000 cGy in 5 weeks.

Long-term complications (months to years later) are caused by injury to late-responding tissues (skin, subcutaneous tissue, muscle, bone, glands, central nervous system). Over time, progressive fibrosis occurs within these tissues. Histologically, the most characteristic delayed radiation lesion seen is eccentric myointimal proliferation of blood vessels (Fig 1). Decreasing the radiation dose per fraction reduces its effects on late-responding tissue. 5

Fig 1.

Radiation effects on capillaries, arterioles, and small arteries. A, With the capillary, the lumen narrows over time because of swelling from the endothelial cells and sclerosis of the vessel wall. A thrombus can form occluding the vessel. B, With the arteriole, edema occurs with the endothelium and smooth muscle, thus narrowing the lumen. Degenerative changes (endothelial proliferation, subendothelial deposition of a hyaline-like substance, focal destruction of smooth muscle cells) develop in the vessel wall. C, With the small artery, progressive damage of the endothelium and media occur. Radiation changes (fragmentation of the internal elastic lamella, degeneration of the smooth muscle media with accumulations of a hyaline-like substance, fibrosis of the adventitia) occur. (With permission from Anderson WAD, Kissane JM, editors. Pathology. St Louis: Mosby; 1977.)

After radiation, the skin is more susceptible to infection, trauma, and irritation because of reduced vascularity and increased fibrosis. Localized trauma or infection to irradiated skin can create a nonhealing wound. Key tenets in managing previously irradiated skin are to prevent its breakdown and to promptly institute conservative therapy whenever skin injury is present. When a persistent nonhealing skin ulcer is present, malignant recurrence needs to be ruled out. Well-vascularized flaps are often required for coverage after the infection has been controlled; however, these flap incisions can also break down. Currently, the irradiated wound is cared for in a similar manner to other chronic wounds. This is because the exact cellular microenvironment of the irradiated wound remains undefined.

ACUTE VERSUS CHRONIC WOUNDS

A distinction must be made between acute and chronic wounds (ie, irradiated wounds). In the acute wound, inflammatory cells initiate the wound-healing cascade, which produces growth factors that act on the surrounding connective tissue and epithelium. Macrophages coordinate and sustain the wound-healing response, releasing numerous growth factors to stimulate cell proliferation, matrix production, and matrix degradation. In the chronic wound, the normal sequence of inflammatory events is altered or may not be present. As in acute wounds, the cellular repair process is dependent on the wound cellular elements, wound matrix, growth factors, and proteolytic enzymes. 6 However, for unknown reasons, the interaction of these parameters becomes distorted, resulting in delayed healing. 7 The goal in the management of irradiated wounds is to transform the chronic wound state into an acute wound state. This transformation would encourage normal wound healing to proceed (Fig 2). In the past attempts have been made to help transform the chronic wound to an acute healing state. These maneuvers include surgically freshening the wound edges or adding an inflammatory agent (ie, gentian violet, silver nitrate) to the wound to incite an inflammatory response to “jump-start” the healing process. In caring for a patient with an irradiated wound, physicians must ensure a proper healing environment by maximizing its wound care management.

PRINCIPLES OF WOUND CARE

In the early 1960s, a moist wound environment was found to give the most optimal healing. Winter 8 showed that the rate of reepithelialization was twice as fast for wounds covered with occlusive moist dressings than for air-exposed wounds. This is because in a moist occluded environment, epithelial cells travel faster and a shorter distance for epithelialization to occur. In air-exposed wounds, migrating epidermal cells need to take a circuitous route beneath a crusted scab and devitalized dermis to reach their destination. From these discoveries, moisture-retentive dressings began in the early 1970s and continue into the present. Table 1 categorizes the purpose and types of the wound products.

With some of the newer dressings being called “the intelligent dressings” or “the sophisticated gauzes,” a new approach for dressing selection is emerging for all wounds. Many of these new dressings are occlusive or semiocclusive. Despite these new dressings, the principles of optimal wound healing still remain.

Comparisons made between oxygen-permeable and oxygen-impermeable dressings indicate that the ability for atmospheric oxygen to traverse through a permeable dressing has little effect on wound healing. 9 , 10 In both dressings epidermal resurfacing is enhanced by the moist environment. 10 The exposure of acute wound fluid in the acute wound is thought to give benefits for epidermal regeneration. 11 However, this same benefit may not be as pronounced with occlusion of chronic wounds. In fact, some studies have implicated possible detrimental effects of persistent chronic wound fluid at the wound site. 7 , 12

Fig 2.

An 82-year-old man had a persistent, chronic, nonhealing full-thickness wound on his scalp after excision of a squamous cell cancer 2 years previously. Ten years previously he had received radiation to his scalp. He had no evidence of tumor recurrence by multiple biopsy specimens. A, Poor granulation tissue formation and bare bone are evident. B and C, After additional outer calvarial bone was burred down and the scalp was kept moist with an antibiotic ointment gauze, the chronic wound transformed into an acute wound with robust granulation tissue formation and later coverage with a split-thickness skin graft. A free flap was not required.

Table 1.

Dressing purpose and product classifications

Purpose of product	Wound product classifications
Cleanse topically	Normal saline, commercial wound cleaners
Absorb exudate	Absorption beads, pastes, and powders; alginates; composite dressings; foams; gauze; hydrocolloids; hydrogels
Cover a wound to allow autolytic enzymes of the wound fluid to self-digest eschar and fibrinous slough	Absorption beads, pastes, and powders; alginates; composite dressings; foams; hydrated gauze; hydrocolloids; hydrogels; transparent films
Topically debride devitalized tissue chemically	Enzymatic debridement agents
Mechanically debride devitalized tissue	Wound cleansers, gauze (wet to dry)
Add moisture to the wound	Gauze (impregnated or with saline), hydrogels, wound care systems (2 part)
Maintain a moist wound environment	Ointments, foams, gauze (impregnated or with saline), hydrocolloids, hydrogels, transparent films, wound care systems (2 part)
Fill dead space	Absorption beads, pastes, and powders; alginates; hydrocolloid pastes; powders; foam; gauze
Cover and protect wound	Composites, compression bandages/wraps, foams, gauze dressings (covers/wraps), hydrocolloids, hydrogels (with covers/borders), transparent film dressings
Protect surrounding skin from moisture and trauma	Moisture barrier ointments, foams, hydrocolloids, securement devices, skin sealants, transparent film dressings

Adapted and reprinted with permission from Krasner D. Dressing decisions for the twenty-first century. In: Krasner D, Kane D. Chronic wound care. 2nd ed. Wayne (PA): Health Management Publications; 1997. p. 139–51.

Table 2.

Tailoring wound dressings according to the particular characteristics of the irradiated wound

Type	Wound description	Dressings to consider	Objective
Necrotic	Wound cavity with excessive yellow exudate, slough, dark eschar (black to tan)	Calcium alginate rope, hypertonic saline gauze, hypertonic gel, enzymatic debriding ointment	To absorb exudate and promote debridement
Granular	Granulating wound, minimal or moderate exudate	Hydrogel gauze, calcium alginate	To provide a moist environment
Requiring reepithelialization	Pink, shallow	Hydrogel sheet, hydrocolloid, foam when wound is moist	To maintain moisture, promote resurfacing, and protect new epithelium

One major concern about using occlusive dressings is infection. Occlusive dressings are contraindicated in wounds that are clinically contaminated. A distinction must be made between wound colonization and wound infection. A wound that is colonized does not have invasion of bacteria into viable tissue and elicits a minimal host immune response. A wound infection involves bacterial binding, invasion, and replication within the host tissue, causing a strong host immune response. 13 Infection can delay wound healing, whereas colonization may not. Infection can be differentiated from colonization by a quantitative wound culture (>10⁵ colonyforming units of specific pathogen per gram of tissue). 14 Quantitative cultures are different from standard swab cultures in that the wound is thoroughly cleansed before the specified volume, weight, or surface area of the wound is obtained. They can be tissue biopsy specimens, needle aspirates, or quantitative swabs. 15

Presently, it is possible to tailor dressing decisions according to the particular characteristics of each individual wound to optimize the healing. Because granulation tissue must form before reepithelialization occurs, proper steps in dressing care are important. In chronic full-thickness wounds the selection for the proper dressing can be modified according to the wound characteristics, patient, and environment. An example would be a patient with a small infected pharyngocutaneous fistula. The first objective would be to clear the infection, the second would be to induce granulation tissue, and the last, after sufficient granulation tissue buildup, would be to induce reepithelialization. No single dressing currently can fulfill all of these criteria. Table 2 describes how a dressing can be selected according to its wound characteristics. The major tenets for optimal local wound care management are described in Table 3. 16

Table 3.

Major tenets for optimal local wound care management

Tenet	Rationale
Debride necrotic tissue	Removing necrotic tissue minimizes bacterial growth
Identify and treat infection	Infection inhibits all stages of wound healing
Pack dead spaces lightly	Tightly packed spaces hinder wound cavity contraction
Divert any salivary drainage away from the wound	Salivary seepage will increase bacteria wound load
Drain any excess fluid collection	A fluid collection becomes a reservoir for infection
Absorb excess exudate	Excess wound exudate will macerate surrounding skin
Maintain a moist wound surface	Moist surfaces enhance granulation tissue formation and epithelial cell migration
Maintain open fresh wound edges	Closed, well-epithelialized wound edges prevent epithelial migration across the wound surface
Protect the wound from trauma and infection	Trauma and infection will damage new tissue
Insulate the wound	Warmth maximizes blood flow and cell function to optimize wound healing

Adapted with permission from Bryant R. Science and reality of wound healing—wound healing: state of the science. Symposium of the Wound Healing Society and the Wound, Ostomy, and Continence Nurses Society, June 12, 1997. Nashville (TN): Wound, Ostomy, and Continence Nurses Society; 1997. p. 196–200.

CHOOSING THE OPTIMAL WOUND DRESSING

In the irradiated wound the general principles of wound care management apply except that adhesives should be used sparingly to prevent epithelial injury. To establish a moist wound-healing environment, 6 major moisture-retentive dressing categories exist, encompassing a large number of products. 17 Maximal efficacy for choosing the appropriate dressing depends on satisfying the needs of the wound by thorough assessment. Thus the type of dressing chosen should be matched to the wound characteristics.

Gauze Dressings

Moist gauze dressings are commonly used dressings for treating open wounds. Used in a wet-to-dry or a wet-to-damp fashion, they absorb exudate and can help remove nonviable tissue. Gauze is a useful wound filler, and a variety of solutions or gels can be added to it to maintain a moist wound surface.

Indications for use. They are used on full-thickness, exudative, necrotic wounds with dead space. Wet-to-dry dressings adhere to the wound bed, and when the dressing is changed, nonviable tissue is removed. One disadvantage inherent with this dressing is that when it is removed, the dry gauze nonselectively debrides the wound and frequently sticks to healthy granulation tissue, injuring it and the epidermis. When allowed to dry, it will desiccate any healthy tissue in the wound and may cause bleeding and pain to the patient on removal. Newer, moisture-impregnated gauzes containing saline solution or hydrogel can minimize drying. Wet-to-damp dressings provide a better moist wound environment than wet-to-dry dressings. To achieve a wet-to-damp dressing, a sufficient amount of saline solution must be applied, in addition to the dressing being rewetted between dressing changes as needed.

Guidelines for use. Fine mesh gauze packing should be loosely placed to allow for adequate tissue perfusion. Care must be taken to avoid maceration of the surrounding skin, and use of a barrier ointment or skin sealant should be considered. Normal saline solution is the most commonly used wetting agent. Cytotoxic agents should be avoided. Goals of the moist environment are to hasten debridement, promote granulation tissue formation, and prevent wound dessication.

Effectiveness and expense. It is the most economical and accessible dressing material available to maintain moisture in a wound. However, saline dressings require close monitoring, frequent inspection, and more frequent dressing changes to prevent gauze drying and wound dessication.

Transparent Film Dressings

Transparent film dressings are thin, transparent moisture-retentive dressings made of polyurethane. They are conformable, water resistant, and impervious to bacterial penetration, and they allow the wound to be seen without removal of the dressing. They are semi-permeable, with the ability to transmit oxygen, water vapor, and carbon dioxide. Drainage will collect under the membrane.

Indications for use. Films are used on superficial and partial-thickness wounds with little or no exudate. They are also applied over dry necrotic eschar to provide a physiologic environment that supports autolytic debridement. They are sometimes used as secondary dressings over gauze or calcium alginate packing.

Contraindications to use. They should not be used on infected and exudative wounds. Film dressings must be used with care on thin, fragile skin.

Guidelines for use. The frequency of dressing change depends on the amount of drainage. The dressing is changed when leakage occurs, or every 1 to 7 days. Use of a skin sealant on intact surrounding skin before dressing application will help prevent maceration and skin stripping. The dressing should cover the wound and 2 cm beyond the intact skin.

Effectiveness and expense. Effective for very low exudative wounds with surrounding dry skin surfaces to allow for adherence of the film dressing. The film dressing cost is moderately higher than that of normal saline gauze.

Foam Dressings

Foam dressings are used as primary dressings and as wound fillers. They are composed of polyurethanes and vary in conformability, permeability, and absorbency. Foams maintain a moist environment and are nonadherent, although some are available with adhesive borders. They support autolytic debridement, and some are impregnated with surfactants and glycerin.

Indications for use. They are useful on partial- and full-thickness wounds with small-to-moderate exudate, moist necrotic slough, or clean granular wound beds.

Contraindications for use. They are not to be used on nonexudative wounds.

Guidelines for use. Most foams require changing every 1 to 5 days depending on the amount of drainage and absorbency. Foams with adhesive borders should be used with caution on irradiated fragile skin. They are very useful on skin breakdown sites from tracheostomy tubes in that they help cushion the ulcer, absorb drainage, and increase patient comfort. Typically, these dressings are secured with tape, wrap bandages, or stretch netting.

Effectiveness and expense. They are very effective for absorbing exudate and protecting the skin surfaces from maceration. The foam dressing cost is significantly higher than that of normal saline gauze.

Hydrocolloid Dressings

Hydrocolloid dressings have a water-impermeable polyurethane outer layer and an adhesive hydrocolloid inner layer that does not adhere to the wound bed. They maintain a moist wound environment, promote autolytic debridement, and insulate the wound bed. They are available in opaque and transparent wafers, paste and powder forms. Most hydrocolloid dressings are occlusive and do not permit oxygen to diffuse to the wound from the external environment. They serve as very good microbial barriers, protecting the wound from the external environment.

Indications for use. Hydrocolloids are indicated for partial-thickness wounds and shallow full-thickness wounds with clean or necrotic bases.

Contraindications to use. Hydrocolloid dressings should not be used on heavily exudative or infected wounds. For cavitary wounds, they should be used with a packing or filler agent to fill the dead space.

Guidelines for use. Frequency of the dressing change (typically 3 to 5 days) is based on the amount of exudate the wound produces. The dressing should be changed when it begins to leak, loosen or wrinkle. The wafer dressing should extend past the wound perimeter, approximately 2 cm onto healthy intact skin. Use with caution if the skin surrounding the wound is fragile. Use of a skin sealant on the surrounding skin will help prevent skin stripping and maceration. The wafers work well on areas of moist desquamation and are used to secure other types of dressings. They require low maintenance and provide a high degree of patient comfort. One disadvantage of hydrocolloids is that because most are opaque, wound inspection can be difficult.

Effectiveness and expense. These dressings provide an extremely effective environmental barrier for protecting the wound and for holding other dressings in place. The cost of hydrocolloid dressings is significantly higher than that of normal saline gauzes.

Calcium Alginate Dressings

Alginates are used as wound fillers and dressings for partial- to full-thickness wounds. Their main purpose is to give absorption to exudative wounds and act as fillers to eliminate dead space. Calcium alginate dressings are derived from seaweed and are available in absorbent forms of rope, ribbons, and sheets. As the alginate absorbs the wound exudate, it transforms into a viscous hydrogel at the wound interface. Alginates are nonocclusive, nonadhesive, moisture-retentive dressings.

Indications for use. Alginates are used on partial-and full-thickness wounds with moderate-to-large amounts of exudate.

Contraindications to use. Alginates are not to be used on dry or low exudative wounds because wound fluid is required to make their fibers transform into a moist gel. They should not be used in blind sinus or fistula tracts.

Guidelines for use. Alginates are applied dry once or twice a day. If the alginate dressing adheres to the wound when the dressing is changed, it must be irrigated with normal saline solution, and another moisture-retentive dressing may be required. A secondary dressing is always necessary to secure the alginate dressing in place.

Effectiveness and expense. This dressing is very effective for absorbing exudate in cavitary wounds. Its cost is significantly higher than that of normal saline gauze.

Hydrogel Dressings

Hydrogel dressings are water- or glycerine-based dressings. They are available as amorphous gels, sheet dressings, and impregnated gauzes. The gels are moisture retentive, nonadherent, nonocclusive, and highly conformable. Gels can give a cool, soothing sensation to patients and offer some pain relief. Hydrogel dressings are effective in promoting debridement, granulation, and reepithelialization.

Indications for use. They are used on granular and necrotic wounds of all depths.

Guidelines for use. Sheet forms are used on partial-thickness wounds and are usually changed every day. Amorphous gels and impregnated gauzes are for full-thickness and cavitary wounds. They require a secondary dressing to secure them in place and are changed daily.

Effectiveness and expense. This is a very effective modality to induce granulation tissue formation in partial- and full-thickness wounds. The hydrogel dressing cost is moderately to significantly higher than that of normal saline gauze.

COST CONSIDERATIONS FOR DRESSINGS

All of the newer dressings are more expensive than the traditional saline gauze dressing. However, cost concerns must look at other important factors beyond the price of each individual dressing. These factors include the frequency of changes, which varies considerably from 2 to 3 times a day with saline gauze to every 3 to 5 days with hydrocolloids. Cost is also affected by the skilled care a patient may require to change the dressing. The cost of twice a day home visits for changing saline gauze dressings is far greater than a visit every 3 to 4 days for another dressing type. Patient comfort and improved quality-of-life issues are difficult measures to assign a cost. The benefits of increased patient comfort and less time spent focusing on wound care are often positive outcomes at a higher cost with the newer dressings.

OTHER ISSUES FOR WOUND CARE

Wound cleansing is another important issue for effective wound management. A frequent quote in wound cleansing has been, “Don't put in a wound what you wouldn't put in your own eye.” The strength of wound-cleaning solutions is directly proportional to their toxicity to cells. Thus the cleaning capacity of the solution must be weighed with the potential toxicity to the normal cells in the wound. Cleaning solutions can be classified as either wound or skin cleansers. Skin cleansers (ie, Hibiclens, Betadine, Dakin solution, hydrogen peroxide) are not recommended for repetitive routine rinsing in wounds because of their toxicity to normal cells. 18 Normal saline solution is a more acceptable wound cleanser.

All chronic wounds contain bacteria. The most important factor in reducing the level of bacterial contamination in chronic wounds is to remove all devitalized material. A chronic wound that is kept clean should show signs of healing within 4 weeks. 19 , 20 If adequate healing does not proceed, the wound must be properly reevaluated for (1) adequate nutrition, (2) sufficient blood supply, (3) proper wound management, (4) wound pressure relief, and (5) bacterial contamination. In addition, in all nonhealing wounds, neoplastic recurrence needs to be ruled out.

CONCLUSIONS

Overall wound management for previously irradiated wounds includes the following.

Adequate debridement and local wound cleansing with avoidance of salivary contamination.

Accurate assessment of the wound type, depth, and degree of exudation.

Appropriate choice of dressing based on wound assessment. Over time, the wound should be reevaluated, with dressing modification as required.

Encouragement of granulation tissue formation and reepithelialization once a clean wound has been achieved. In large defects, coverage with well-vascularized tissue should be considered.

Currently, wound-healing management is undergoing an evolution. In the past physicians would take a passive approach to a wound by keeping it clean, covering it, and hoping it would heal. Since 1970, new wound dressings have been tailored to maintain a moist environment, whereas others absorb exudate to create an optimal wound milieu. Although these dressings attempt to optimize the wound environment, none actively induces cellular growth. The next era of wound repair will involve directing selected cells within a wound to replicate and migrate to improve wound healing.

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