Wound Dressings

Donor Site Wound Dressing

The type of wound dressing has an important, but unquantified, effect on healing. A bolster together with a splint remains the conventional method of radial immobilization. The use of a NPWD, also known as vacuum assisted closure (VAC), at the radial donor site was first described by Avery in 2000.^145,146 Previous studies had indicated this technique may expedite early revascularization and healing of skin grafts, although not all studies have supported these findings.^147-150 The NPWD is now in common use in a wide range of surgical practice. A 2014 Cochrane Database Systematic Review on the use of NPWD to promote healing by primary intention noted that rates of graft loss may be lower but highlighted the need for high quality randomized trials, and a similar review of complex wounds healing by secondary intention is planned.¹⁵¹ The NPWD has been successfully used in the latter situation at the radial donor site.^123,152 The NPWD closely adapts the skin graft to the recipient site, minimizing movement and eliminating dead space (see Figure 35-22). In contrast to conventional dressings, the wrist may be immediately mobilized.¹⁰ Excellent rates of graft healing at both the subfascial and suprafascial donor sites with either partial or full thickness skin grafts have been described, together with superior results in a small retrospective comparison with the conventional bolster technique.^{11,123,145,146,153} In contrast, a prospective randomized study failed to show a benefit with the NPWD, but the skin graft complication rates were especially high and perhaps the surgical technique was poor; one-third of patients were lost to follow-up (presumably because of no complications), and the study was statistically underpowered.¹⁵⁴ In the practice of the author, the combination of the suprafascial donor site managed with a NPWD has almost eliminated significant donor site complications (see Table 35-1).

5.4.1 Alginates

Wound dressing based on alginic material is well known, in the literature as well as from a commercial point of view, in wound management.¹⁴ Alginates are linear copolymers of β-(1-4)-linked d-mannuronic acid and α-(1-4)-linked l-guluronic acid units, which exist widely in many species of brown seaweeds. Alginate fibres can be prepared by extruding solutions of sodium alginate into a calcium salt solution bath or an acidic solution to produce the corresponding calcium alginate or alginic fibres, respectively.

Typically, the degree of crystallinity of the alginate fibres is of the order of 30% with a degree of water absorption of 90% after immersion in water. Fibres of this type have been used extensively in wound dressing applications owing to their excellent biocompatibility, non-toxicity, and potential bioactivity. Alginate fibres, typically as a calcium salt, interact with the wound exudates to form a moist gel, as a result of the ion exchange between the calcium ions in the fibre and the sodium ions in the exudates.¹⁵ The gel-forming property of alginate eliminates fibre entrapment in the wound and helps in removing the dressing without much trauma, thus, reducing the pain experienced by the patient during dressing changes.¹⁶ Such gelation provides the wound with a moist healing environment, which promotes healing and leads to better cosmetic repair of the wound. The gel-forming property provides a moist environment that leads to rapid granulation and re-epithelialisation.¹ In a controlled clinical trial, a significant number of patients dressed with calcium alginate was completely healed at day 10. In another study with burn patients, calcium alginate significantly reduced the pain severity and was favoured by the nursing personnel because of its ease of care.

This in situ generation of a moist healing environment and the consequent high absorbency of the alginate dressings are two of the outstanding properties, which make the alginate dressing one of the most versatile wound dressings available today. In addition, alginate-containing dressings have been demonstrated to activate macrophages within the chronic wound bed and generate a pro-inflammatory signal which may initiate a resolving inflammation characteristic of healing wounds.¹⁷ Therefore, many commercially available wound dressings used in wound management contain calcium alginate fibres.

The alginate dressings currently available on the market have mainly been manufactured from fibres of calcium alginate or sodium–calcium alginate. Depending on the quantity of the mannuronic or guluronic acid derivatives in the fibre-forming material, the fibres change into gel form to varying degrees.^18,19 Modern active dressings, besides their function of providing a moist wound environment, should also be adapted to the stage of wound healing and, on this basis, capable of stimulating the granulating process or protecting against the damage of a newly formed tissue.²⁰

A possible advantage of alginate fibres is that they are relatively easy to modify by incorporating appropriate metal ions, microelements or other biologically active substances that accelerate the healing process or have bacteriostatic properties.²¹

As an alternative to standard alginate dressing, new alginate dressings that have been trialled are said to have superior properties, e.g., zinc alginate fibres. The replacement of sodium ions with zinc ions during solidification allows zinc alginate fibres with suitable properties for medical applications to be prepared. Zinc alginate fibres show high moisture absorption, an acceleration of the wound-healing process and antibacterial character resulting from the presence of zinc ions. These fibres can be used for the manufacture of dressings to be used for wounds in subsequent healing stages. The bacteriostatic effects of zinc can be increased or extended by incorporating typical bactericidal or fungicidal agents into fibres during the spinning stage.

In addition to zinc ions, silver ions have been found to have antibacterial effects on some microbes. The silver salt is normally seen as the most effective antimicrobial agent in the treatment of burn patients.²² The so-called antibacterial fibres can be obtained by treatment with an aqueous solution of silver nitrate. The calcium alginate fibres were converted into calcium/silver alginate fibres by the treatment with silver nitrate. The calcium alginate fibres have little antibacterial activity, but the calcium/silver alginate fibres have good antibacterial activity toward Staphylococcus aureus.²³

Various alginate wound dressing materials have been commercially utilised and reviewed in the literature. Some commercial alginate wound dressing materials include: Algisite® (Smith & Nephew), Kaltostat® (ConvaTec), Tegagen® HG or HI (3 M Health Care), Comfeel SeaSorb® (Coloplast AS), AlgiDERM (Bard), Algosteril® (Johnson & Johnson), CarraSorb H® (Carrington), CURASORB® (Kendall), Dermacea® (Sherwood-Davis & Geck), Fybron® (B. Braun), Gentell® (Gentell), Hyperion Advanced Alginate Dressing® (Hyperion Medical Inc.), Kalginate® (DeRoyal), and Maxorb® (Medline).

Postoperative Care

Wound dressing with the Abbé is straightforward. The pedicle connecting the upper and lower lips is self-contained and a circumferential dressing (like the PFF) is contraindicated. Patients are warned not to consume hot solids/liquids until anesthesia dissipates and semisolids or puréed foods may be needed. Patients may still converse. A standard postoperative regimen for this author includes antibiotics and analgesics in liquid formulations for ease of administration. Although nausea from surgery is uncommon, nausea and vomiting from the narcotic analgesics may occur and a preemptive prescription is recommended. Antivirals are generally not necessary.

Dressing

Wound dressings should be chosen to address exudate control, wound protection, and pain relief. The goal is to provide a moist wound environment to promote granulation tissue formation and epithelialization. Using hydrocolloids, hydrogels, alginates, transparent films, and other bandages provides coverage and may promote the function of these enzymes. However, excessive exudate can saturate the wound bed, diminishing these beneficial properties, and macerate surrounding tissue, making it more prone to injury. Finally, choosing a dressing that does not adhere to the wound bed can be important to assure that it does not disrupt reepithelialization when it is removed.

Accurately identifying the key cause of wounds is essential in the management of leg ulcers though many wounds are complex and may be of more than one etiology. The following are specific approaches to different leg ulcers.

Wound Dressings.

Wound dressings are identified as primary or secondary. Primary dressings are applied directly to the wound bed and secondary dressings are used to anchor or contain the primary dressings. The function and selection of the primary dressing is based on the wound characteristics (e.g., tissue type, healing phase, bacterial count). The function and selection of the secondary dressing is based on the purpose and consistency of the primary dressing and on the patient's functional status. The appropriate wound dressing will likely change as the needs of the wound change and may vary among different areas of a wound that are in different healing phases. Custom dressings consisting of two or more primary dressings and one secondary dressing may be indicated in a single wound, provided the primary dressings do not inactivate each other. The informed clinician, being resourceful with the available supplies, matches the primary dressing to the wound needs and the secondary dressing to the patient needs (Table 28-13).

Selecting the optimal dressing for a PU can appear to be a daunting task given the myriad of products available. A few basic principles, however, can make the decision quite simple. The advantages of a moist wound environment over dry or wet-to-dry methods are well documented,¹⁴⁴ therefore any dressing selected should keep the wound bed moist while keeping the periwound skin dry to protect it from maceration. If the wound bed tends to be dry, dressings that add moisture are advised. If there is drainage, the dressing should manage any excessive moisture. Periwound skin should also be protected with moisture barrier creams, protective films, or hydrocolloid dressings. When dressing a PU with a cavity, the cavity should be lightly filled with the dressing material so that there is no dead space to collect exudate and increase the risk of infection or abscess formation. Self-adhesive dressings are recommended to avoid applying tape to the periwound skin because removing tape can cause skin tears. Many of the advanced dressings can remain in place for 24-72 hours or longer, reducing caregiver time and facilitating wound healing by limiting wound bed disturbance, and as a result, thereby decreasing the overall cost of treatment.

Although wound dressings that facilitate wound healing by creating a moist wound environment are currently accepted as standard of care in the medical community, some of the newer advanced biological topical medications and dressings are more controversial. Becaplermin gel (Regranex) is a platelet-derived growth factor that has been studied extensively for the treatment of diabetic ulcers.^145-148 One study reported that becaplermin gel is also effective in the treatment of PUs. In a randomized controlled trial of 124 adults with PUs, topical treatment with becaplermin gel was compared with a placebo gel until healing was achieved or for a maximum of 16 weeks. Becaplermin significantly increased the incidence of complete or >90% healing and significantly reduced the ulcer volume at end-point.¹⁴⁹ In addition, a meta-analysis of four phase II and III trials strongly supports the efficacy of becaplermin gel for facilitation of wound healing.¹⁵⁰ Although becaplermin gel is currently the only topical growth factor commercially available, topical formulations of transforming growth factor-beta 3¹⁵¹ and nerve growth factors^152-154 are being investigated specifically for use with PUs with promising results.

Silver, in the forms of dilute silver nitrate liquid and silver sulfadiazine cream, has been used as a topical antimicrobial medication for wound management for many years, especially with burn related wounds.¹⁵⁵ Silver sulfadiazine cream has also been used for treatment of PUs because of its ability to keep the wound bed moist and decrease bacterial load. Because the silver in silver nitrate liquid and silver sulfadiazine cream is released and absorbed quickly, these preparations must be applied twice daily, and an absorbent secondary dressing may be needed to manage exudates in moderate to heavily draining wounds. A new topical silver preparation, nanocrystalline silver, has recently become popular for wound management because the silver in it is absorbed only by the local tissue not systemically, making it safe for use on patients with end-stage renal disease. The nanocrystalline silver can also be incorporated into an absorbent dressing (e.g., hydrofiber or foam) and thus remain in place for 2-4 days. A laboratory study of a nanocrystalline silver-coated dressing demonstrated that the concentration of silver released over a 24-hour period was 70 mg/ml and inhibition of microbes (P. aeruginosa and Staphylococcus aureus) lasted for a minimum of 9 days with one application. In addition, the silver was “very rapidly” bactericidal.¹⁵⁶ In another study, the rat burn model was used to compare the effectiveness of nanocrystalline silver dressings with liquid silver nitrate. The mean percentage survival rate of the control group was 5%, the silver nitrate group was 0%, and the nanocrystalline silver group was 85%, suggesting that the slow-release silver is more effective than traditional methods in controlling sepsis that result from burn wound infections. Additionally, the authors state that because nanocrystalline silver acts rapidly against bacteria, the risk of bacterial resistance to the dressing is minimized.¹⁵⁵ An uncontrolled, prospective study of 29 patients with chronic ulcers, including 2 with pressure ulcers, showed marked clinical improvement of the wounds treated with nanocrystalline silver dressings, including decreased exudate, decreased purulence, and a decrease in wound surface bacterial load measured by semiquantitative swabs.¹⁵⁷ An additional positive effect of nanocrystalline silver was demonstrated in a pilot study of eight patients with chronic wounds in which the matrix metalloproteinases (MMPs) in chronic wound fluid was measured before and after treatment. A marked decrease in MMPs was noted in the first 2-3 days of treatment and was sustained with continued use of the nanocrystalline dressing.¹⁵⁸ (MMPs have been shown to degrade extracellular matrix and inhibit wound healing.) Antimicrobial activity of four silver-containing dressings against three microorganisms: A gram-positive bacterium, S. aureus, a gramnegative organism, and Escherichia coli was studied.¹⁵⁹ Acticoat (Smith & Nephew, Largo, Fla) produced the most rapid antimicrobial effect in vitro, which was ascribed to the rapid release of relatively large concentrations of highly active silver ions. Contreet-H (Coloplast, Marietta, Ga), a foam-based dressing, had a broad antimicrobial activity similar to Acticoat but with a slower onset of action. Actisorb Silver 220 (Johnson & Johnson, New Brunswick, NJ), a gel-based dressing, was less effective in the wound itself but was capable of removing bacteria from exudate. Avance (SSL International, UK) was minimally effective.

A study of nanocrystalline silver in a sodium carboxymethylcellulose fiber dressing (Aquacel Ag, ConvaTec, Princeton, NJ) has implications for the treatment of PUs because of the dressing's absorbent qualities and its ability to be used to fill cavity wounds. A pilot study of 18 participants with chronic leg ulcers, all of whom were treated for 28 days with nanocrystalline silver in sodium carboxymethylcellulose fiber dressings, yielded the following findings: The overall mean wear time was 3.59 days, no leakage was observed in 69.8% of the dressing changes, pain scores were significantly reduced from baseline including with dressing changes, 39% of the wounds showed marked improvement and 56% showed mild improvement, and 2 of the 11 wounds infected at baseline resolved without the use of systemic antibiotics.¹⁶⁰ These studies indicate that nanocrystalline silver, particularly when used in conjunction with an absorbent dressing, may decrease the bacterial load of PUs, promote wound healing, and be cost-effective because fewer dressing changes are required during the treatment period.

INDICATIONS

There is no single ideal product available that provides all these functions at once, but the clinician should consider carefully which characteristics of the dressing are the most important for the patient's wound. The wound treatment plan should consider factors such as the cause, severity, environment, size and depth, anatomic location, volume of exudate, and the risk or presence of infection. Patient considerations such as medical status, preferences, level of comfort, and cost-benefit analysis must also be taken under advisement. The final factors to consider are the availability, durability, adaptability, cost, and uses of the wound care products.

Wound Healing

Wound dressings are often removed during therapy in order to assess the incision and the skin. A thorough wound assessment should include the anatomic location, measurements (length, width, and depth in centimeters), color and quality of the wound (i.e., closed incision), type and color of exudate, odor, pain, and a description of the periwound skin.¹² Additional assessment data may be required depending on the type and character of the wound, and treatment protocols may vary according to physician or facility preference. Therapists should feel comfortable cleansing the wound and reapplying new dressings. Wound débridement is occasionally required, and the therapist may collaborate with the physician or the wound specialist to determine appropriate débridement practices during dressing changes.

A significant client-centered concern during the acute postoperative phase is pain. Initial dressing changes may be painful for the client, leading to anxiety for subsequent treatments. Physicians may prescribe pain medications for dressing changes. Nonpharmalogic approaches to pain management should include the use of nonadherent, atraumatic dressings, education, empowerment, and anxiety reduction.¹²

In general, closed incisions should be treated with nonadherent dressings or they may be left open to air after 1 to 3 days postoperatively. If they are located directly under a prosthesis or other device, they may require additional protection. Skin grafts need to remain covered with nonadherent dressings for several weeks postoperatively, and measures should be taken to avoid shearing forces along the site of the graft.

Temporary Skin Substitutes and Dressings

Partial-thickness wounds remain confined to the dermal part of the skin. Usually, these wounds have a good healing potential because epidermal cells present in (remnants of) sebaceous glands, sweat glands, and hair follicles are available to close the wound.

In these wounds, the main demands to reach pain reduction and high-quality wound healing without scarring is to warrant undisturbed wound healing. A moist environment and protection against bacterial invasion are the most important qualities that need to be provided.

Modern wound dressing are able to fulfil these requirements. Generally, membranous dressings such as hydrocolloids and hydrofibers fulfill these requirements better than topical antimicrobial creams such as silver sulfadiazine (SSD) cream.^4-6 The main indication for temporary skin substitutes is partial-thickness wounds, of which donor sites are a special category, but essentially are similar wounds.