Vet Times The website for the veterinary profession https://www.vettimes.co.uk DEVELOPMENTS IN WOUND CARE Author : JOHN WILLIAMS, ANNA CONDON Categories : Vets Date : August 11, 2014 JOHN WILLIAMS MA, VetMB, LLB, CertVR, DipECVS, FRCVS ANNA CONDON MVB, MRCVS review the numerous techniques and products used in the management of open wounds and offer an update on developments in the area Summary Open wound management is an integral component of veterinary medicine and the choice of what to use and where it is appropriate depends on a variety of factors and the type of wound involved. This article highlights the commonly used and newly emerging therapeutic options for open wound care and their respective uses. Balancing the use of debriding agents and nourishing wound products is critical in wound therapy. The advent of relatively new techniques, such as negative pressure wound therapy (NPWT) and hyperbaric oxygen chambers, are briefly discussed, as are the use of easily accessible products such as silver impregnated products and hydroactive dressings. The authors mention both products that are familiar and unfamiliar to them to address as many options available to the general practitioner as is possible. The best approach to wound care is surmised in an easy to reference table to aid veterinary surgeons to consider all aspects of the healing process sensibly and efficiently. Key words debridement, dressing, granulation, antimicrobial, negative pressure wound therapy (NPWT) 1 / 20
WOUND care is a challenging task in the veterinary profession. Developments in this area are relatively few, with most products a revival or improvement of already established methods. With previous literature discussing the use of either wet-to-dry dressings or dry-to-dry dressings, this article focuses on more recent and developing methods for open wound care. Open wound management product/techniques include: negative pressure wound therapy (NPWT)/vacuum-assisted closure (VAC); hydroactive dressings; honey; alginates; enzymatic debriding agents; tie-over wound dressings; medical maggots; skin stretching techniques; laser therapy; silver impregnated dressings; acupuncture; and hyperbaric oxygen. NPWT NPWT is a novel technique used to increase the speed of wound healing through the use of an airtight vacuum. Sub-atmospheric pressures are applied to the wound, resulting in wound protection, drainage and accelerated wound healing. NPWT is implemented through the use of commercial or improvised systems; the wound is packed with gauze or a foam dressing, covered with an adhesive drape and connected to an adjustable suction tube and container. PICO (Smith and Nephew) is a single use portable pump device that 2 / 20
uses pressures of -80mmHg to maintain a negative pressure and remove any exudate through evaporation and absorbency. A four-layer dressing is placed in an airtight manner over the wound bed and the battery-operated pump activated for up to seven days. Each of the layers has a specific use in promoting rapid wound healing through minimal tissue damage, absorption of exudate, high moisture vapour transmission and negative pressure. Alternatively, Curato (Infiniti Medical) is a veterinary-specific portable device that allows variation of pressure between -50mmHg and -150mmHg and only uses one layer of foam covered by a polyurethane dressing. NPWT is marketed for use in all kinds of open wounds, from acute and chronic trauma wounds and burns to chronic ulcers and surgical incision sites (Figure 2). Hydroactive dressings Hydroactive dressings are readily available and have an absorptive capacity, acting as a desloughing agent facilitating gentle wound debridement on removal. Hydrogels are placed directly on to the wound bed under gauze swabs or absorptive non-adherent dressings. Commercial and natural methods of this are available through the use of Intrasite gel (Smith and Nephew) and honey/sugar pastes, the latter of which the author rarely uses. Sheet hydrogels, such as NU-GEL Hydrogels (Systagenix) or Intrasite gel, are very suited to wounds with large defects/cavities. Hydrogels tend to absorb minimal amounts of exudate whereas hydrocolloids absorb larger amounts and care must be taken to avoid excessive granulation with these dressings. Hydrocolloid dressings are made up of polymers suspended in an adhesive matrix. They adhere to wound edges and are left in situ for two to three days, providing a moist wound environment while absorbing exudate and preventing strike-through, therefore avoiding iatrogenic damage to granulation tissue. They interact with wounds to aid rapid epithelialisation. Most are waterproof, making them highly suitable for veterinary patients. Honey Honey is noted to be an antimicrobial, anti-inflammatory antioxidant that aids debridement as a hydrogel. When used topically, honey decreases inflammatory oedema, hastens sloughing of necrotic tissue while nourishing the wound and speeding granulation and epithelialisation. Manuka honey has purported sustained antimicrobial effects, making it a very popular choice in human medicine worldwide. The use of honey products in veterinary wounds is widely supported (Figure 3). One specific product, MediHoney, from Australia, has been reportedly successful at clearing an MRSA infection in a severely immunocompromised human patient. Many anecdotal reports of 3 / 20
honey exist and its wound healing properties in both human and veterinary literature, but only the advent of medicinally prepared honey can prove its use in both fields of medicine. Alginates Alginates are salts of alginic acid, a colloidal substance from brown seaweed; used in the form of calcium, sodium or ammonium alginate, as foam, clot or gauze for absorbable surgical dressings. When placed over a moist wound, an ion exchange reaction occurs between calcium in the alginate and sodium in the wound fluid, producing soluble calcium-sodium alginate, a gelatinous mass that helps to maintain a moist environment and facilitate autolytic debridement. It is important to cut the dressing to the appropriate size because larger dressings can lead to maceration of healthy skin in the surrounding area due to their absorptive nature. Some studies praise the beneficial acceleration of wound healing by alginates whereas others have reported long-term fibrous debris resulting in foreign body reaction and others have suggested an inhibitory effect on the production of keratinocytes. Alginates are most suited to moderately exudative wounds early on in healing. Enzymatic debridement Enzymatic debridement is a highly selective method of wound debridement that uses naturally occurring proteolytic enzymes that are manufactured by the pharmaceutical and health care industry specifically for wound debridement. The use of exogenous enzymes, working in conjunction with endogenous enzymes, leads to a clean wound bed with a quicker time period to granulation and hence, epithelialisation and wound remodelling. It is suggested they are beneficial in sinus wounds, although the authors do not use these routinely. There is much debate as to their true efficacy. Tie-over dressings Tie-over dressing is a straightforward technique of preplacing loop sutures around a wound bed where adherent dressings or bandaging materials are not ideally placed to remain in position, for example, perirectal traumatic wounds (Figure 4a and 4b). Non-absorbent loop sutures are placed 360 around the wound two to three centimetres apart and the chosen dressing is placed on to the wound. A laparotomy sponge is placed over it to aid positioning and provide a protective layer and this, in turn, is held in place by tying in a figure of eight pattern umbilical cord or a suitable alternative through the loop sutures. Tie-over dressings are generally prepared under a general anaesthetic or sedation at the preliminary wound assessment period and can then be redressed as often as necessary under sedation or on an amenable conscious patient, with the use of appropriate dressings. The authors advocate using surgical staples to hold dressings in place as an alternative. These are quick and easy to apply, and can be very useful for initial wound 4 / 20
management (Figure 4c). Medical maggot therapy Medical maggot therapy uses medical grade fly larvae on chronic wounds to allow enzymatic debridement of necrotic tissue, decrease bacterial contamination and promote the production of a healthy granulation bed through live organisms. The larvae are raised in a sterile environment and fed on sterilised liver. The larvae used (Lucilia sericata is the commonly used specimen) have a broad spectrum of action against Gram-positive and Gram-negative aerobic and anaerobic bacteria, and human literature reports the use of maggot therapy to be beneficial on MRSA-positive wounds. In veterinary medicine only a handful of cases have been documented, but the increase in antibiotic resistance and the increasing demand for organic products and judicious use of antibiotics, may lead to maggot therapy becoming a strong contender for many chronic wounds in the future. Appropriate larvae, which specifically target necrotic or devitalised tissue, should be used. Skin stretching (facilitated wound contraction) For small animal veterinary surgeons skin elasticity is not usually a major concern. Most cats and dogs have readily manipulated skin, which leads to more successful wound closures. However, not all wounds have generous surrounding skin and so the use of skin stretchers to aid second intention healing or for delayed primary closure is employed. If a wound is extensive in a location where lack of skin elasticity prevents primary closure, the use of items such as fabric hook and loop straps to aid the stretching of healthy skin over a granulation bed can be very beneficial. In the author s experience, using tissue glue to secure the fabric hook and loop straps in place is straightforward and this technique can lead to much faster wound contraction and/or facilitate the implementation of a delayed primary closure. These straps can remain in place for up to five days (the tissue glue loses its strength over that time) and allow the user to tighten and adjust them as necessary, leading to progressive wound contraction and closure (Figures 5a and 5b). Low level laser therapy Low level laser therapy is gaining some acceptance in conventional veterinary practice as a therapy for tissue trauma, wounds, granuloma, myositis, tendinitis and so on. Most lasers are said to be effective in treating wounds (surgical, accidental or septic) and 5 / 20
superficial disorders (cuts, bruises, granulomas, ulcers or fistulas). The use of dynamically refined therapy refers to the dose of laser used, the depth it penetrates and the type of delivery mode to the site. K Laser USA s veterinary laser Cube uses wavelengths of 660nm to 905nm to increase oxygen delivery, stimulate microcirculation through heat, localise melanin and further promote cell growth. A wavelength of 660nm is generally advocated for superficial wounds. It is effective and safe. Wound area decreases after two sessions and strength of the peripheral area increases due to growth of collagen tissue. Scarring is minimal. The effects in wound healing are reported as dramatic. Speed of granulation, tensile strength of the scar and speed of resolution are enhanced. Many irradiated septic wounds heal as if by first intention. Laser therapy is not used widely in veterinary patients, but reports show it to be a promising and useful tool. Silver dressings Silver dressings have made a huge impact on wound healing since the appearance of MRSA infection. These biologically active products release silver ions into the wound bed and have a similar antimicrobial effect to that reported in honey-based products. It does not have any antiinflammatory or debridement properties and can sometimes lead to the Argyria effect, which is blackening of tissues both inside and around the wound. This does not impact on wound healing and can be removed via gentle debridement if necessary. Readily available silver products include Acticoat (Smith and Nephew; Figures 6a and 6b), which is available as a sheet dressing, foam dressing or combined with alginate). Flamazine cream (Smith and Nephew), which contains silver sulfadiazine, is used for a wide variety of superficial skin wounds. It is particularly valuable for superficial wounds with eschar formation as it penetrates this and lowers bacterial numbers on the wound surface. Acupuncture Acupuncture, although there are few documented reports of its use in wound healing, is reported to have beneficial effects on the rate of healing when used locally at the wound site. Blood circulation was measured by laser Doppler flowmetry in several ischaemic wounds and results demonstrated a significant decrease in the degree of necrosis versus the placebo group. The placement of acupuncture needles in the wound periphery is the advocated use in this instance. Hyperbaric oxygen therapy 6 / 20
Hyperbaric oxygen therapy is where the patient is placed safely and comfortably in a large chamber with 100 per cent oxygen at a pressure 1.5 to three times that of normal atmospheric pressure for a period of an hour or so a few times a day. It is reported to cause a reduction in swelling, stimulation of new blood vessel formation into the healing/swollen tissue, a reduction in pressure caused by head or spinal cord injuries, improved wound healing, and improved infection control. Hyperbaric oxygen therapy can be of great help to veterinary patients by speeding up the healing process and may reduce or eliminate the need for more invasive procedures such as surgery, resulting in a net savings of time and cost of treatment for pet owners. While a novel technique, it may be a useful tool in the future. With such a wide array of dressings and techniques available (of which those mentioned are only a few of those most widely advocated), it is important the surgeon considers each available option for wound closure before deciding on a course of action. Open wound management is often a long process that can be as large a financial strain on the client as a primary intention method of wound closure. That being said, primary closure dehiscence as a result of attempting a quick fix in the presence of a suboptimal contaminated wound site, is stressful for all involved parties; the patient, the client and the surgeon. Open wound care allows for routine lavage of a contaminated wound bed, therefore diluting the microbial burden further, facilitating judicious antimicrobial use and appropriate delayed primary closure. Therefore, the use of a stepby- step sequential approach (as demonstrated in Table 1) to each individual case is preferred, allowing for the opportunity to adapt the approach to each wound as necessary. Further reading Pavletic M M (2010). Atlas of Small Animal Wound Management and Reconstruction (3rd edn), Wiley-Blackwell. Tobias K M and Johnston S A (eds; 2012). Veterinary Surgery Small Animal Vol Two, Elsevier. Williams J and Moores A (eds; 2009). Manual of Canine and Feline Wound Management and Reconstruction (2nd edn), BSAVA, Gloucester. 7 / 20
Figure 1. The cycle of healing. 8 / 20
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Figure 2. The Curato NPWT device. 10 / 20
Figure 3. Honey-impregnated dressing in place before full circumferential bandage. 11 / 20
Figure 4a. Tail wound before debridement and lavage. 12 / 20
Figure 4b. Post-wound debridement and lavage (tie-over dressings used for several days until healing well, some minor delayed primary closure used at tail base). 13 / 20
Figure 4c. Tail wound when almost healed staple dressing with Allevyn. 14 / 20
Figure 5a. Wound of unknown cause (query antibiotic reaction). 15 / 20
Figure 5b. Combined use of Allevyn absorbent dressing and skin stretching to facilitate closure. The dog made a full recovery with long-term dressing changes and delayed primary intention closure in some areas. 16 / 20
Figure 6a. Debrided and lavaged wound. 17 / 20
Figure 6b. Silver dressing placement. 18 / 20
Table 1. Open wound treatment protocol 19 / 20
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