ABSTRACT: A 2010 national equine wound-care study was undertaken to report on – and clarify – current wound management theories, and review product usage in equine veterinary practice; with an initial report and review of current human wound-care practices Iransposable to equine veterinary practice Results indicate wide-ranging product usage between practices but a small range within practices Many well-established wound-care products are favoured over newer, successful human wound-care practices including topical negative pressure; the wound healing, infection and exudate continuums; and many ol the active products.

Further research is required, especially in terms of case studies and the potential inclusion of recently developed human products. The requirement for independent product and wound healing guidance in veterinary practice is highlighted

Introduction

Increased research in human wound management during the last decade has led to many advances, including the development of new dressings for each wound stage. Much human research is applicable to equine practice, but the transfer remains slow.

This review aims to indicate how aspects of human wound care could be transposed to an equine context and, through use of a survey, to assess the views of clinicians regarding current wound-care practices and preferred dressing choices for wound healing. It aims to highlight areas requiring further education and study in relation to current theories from human wound-care research.

Human wound care in modern practice

Until the 1960s, wound care focused on achieving a clean, dry wound. Winter (1962), Hinman and Maibach (1963) and Dyson et til., (1988) intimated that wounds protected by an occlusive dressing that provided a moist environment healed faster than those left to dry out. This prompted proliferative research producing dressings to provide the optimum environment for wound healing; with results showing that re-epithelialisation rates almost double under occlusive dressings, provided that fluid production and removal is balanced and bacterial colonisation minimised;'

In the early 2000s, researchers began to identify assessment parameters to ensure uniform and consistent treatment of wounds. Wound bed preparation (WBP) was developed (Schultz et al., 2003) and Jones (2004) analysed its implications for practice.

WBP aims to balance the wounds biomolecular environment – removing local barriers to healing -and is used in conjunction with the TIME framework 7: 

· Tissue – necrotic tissue is removed through debridement.

· Infection – appropriate balance of numbers and species of bacteria to allow healing.

· Moisture balance – to manage exudate levels.

· Epidermal advancement – to promote re-epithelialisation. 

Gray el al., (2003) introduced applied wound management (AWM) which is utilised widely in human practice, but not in equine practice.8 It provides three continuums, healing (Figure 1), infection (Figure 2) and exudate (Figure 3) for wound assessment enabling appropriate dressing choice for wound healing progression. These frameworks could be usefully transferred for equine practice.

Figure 1: The Wound Healing Continuum assists the practitioner in assessment of the wound and identification of possible treatment options’

Figure 2: The Wound Infection Continuum

Figure 3: The Wound Exudate Continuum

Black, black/yellow, yellow and yellow/red tissue must be debrided regularly to enable progression. Red/yellow, red and red/pink tissue requires dressings to aid granulation such as protease modulators and pink tissue requires dressings to allow successful, sustained re-epithelialisation.

When assessing a wound, exudate on the dressing – in addition to that seen in the wound – should be noted, as well as the number of dressing changes required in a 24- to 48-hour period. Wounds in each area must be carefully monitored and appropriate dressings applied to prevent maceration of surrounding tissue whilst maintaining a moist environment.

Current dressing types on the market

Absorbents

Non-adherent or petroleum-impregnated gauze absorbent dressings are non occlusive and ideal for the proliferative stage of healing. Gauze dressings can be folded or rolled, covered in hydrogel and stitched to the wound as a stent to protect a wound that cannot be bandaged owing to location.10

Alginates

Derived from brown seaweed with differing compositions according to mannuronic and guluronic acid levels.11 These highly absorbent dressings are used on moderate to heavily exuding wounds. They exchange calcium ions for sodium ions in the wound bed to initiate the clotting cascade.

Antimicrobials and odour control dressings

Various dressings are available to treat infection or colonisation. Martens el til., (2008) discourage use of topical antibiotics or antimicrobial dressings purporting that they increase bacterial resistance.1- However, Loh el al., (2009) contradict this, reporting that silver-containing hydrofibre (SCH) dressings are effective, killing 100 per cent of methicillin-resistant Staphylococcus aureus (MRSA) strains (with or without the silver-resistance g
ene) tested, and overall prevalence of silver-resistance genes was low.13 They comment that topical antiseptic use should be considered before antibiotics in order to reduce the risk of resistance.

Iodine is a useful antimicrobial which will not damage healthy tissue if used correctly and has no reported resistance. Iodine is quickly deactivated in the presence of pus, so has limited use. To remedy this, dressings are available that soak up exudate then deposit iodine in the wound bed.

Equine studies have shown a gauze dressing and secondary gauze wrap impregnated with 0.2% polyhexamathyline biguanide (PHMB) antiseptic to be effective at preventing Pseudomonas aeruginosa and Staphylococcus epidermidis penetrating the bandage from topical contamination.14

Another antibacterial agent used to combat infection is manuka honey. This age-old remedy has recently gained scientific merit being effective against a broad spectrum of organisms, including MRSA, Pseudomonas aeruginosa and vancomycin-resistant Enterococcus (VRE).15 Its antibacterial and anti¬inflammatory properties reduce pain and oedema without adherence and damage to the wound bed.

Charcoal is used to control odour (often indicative of bacterial presence) by attracting malodorous molecules to its surface and adsorbing them via an electrostatic mechanism.16 It is usually integrated within an alginate, foam or low-adherent dressing and may be combined with an antimicrobial.

Film dressings

Used as primary or secondary dressings, polyurethane films are coated with adhesive, are elastic and comfortable but are not absorbent. They allow vapour to permeate thus permitting fluid evaporation whilst maintaining a moist wound environment and are cost effective."

Foams

Formed from polyurethane or silicone into sheet or cavity form, many are self adherent. Silicone dressings prevent the formation of exuberant granulation tissue and reduce scarring, especially in the distal limbs of horses, as reported by Ducharme-Desjarlias el al., (2005) who found the silicone dressing surpassed conventional dressings in preventing excess granulation and improving tissue quality.17

Foams support a moist wound environment, are absorbent, conforming, vapour permeable and provide an effective barrier against bacteria.ls However, some are disadvantaged by being non-adherent, potentially moving away from the wound bed.11 Adhesive dressings are contraindicated after the debridement phase, as they may damage the fragile new epithelium as it forms.

Hydrocolloids

Hydrocolloids (composed of a mixture of pectins, gelatines, sodium carboxy- methylcellulose and elastomers) are occlusive and encourage autolysis; thus debriding ‘sloughy’ or necrotic wounds.19&20 They are indicated for use in clean granulating or sloughy necrotic wounds. (Note that larval therapy is also in resurgence to remove sloughy, necrotic tissue.)

Hydrogels

For use in dry wounds to rehydratc and promote moist wound healing. Manufactured from three-dimensional cross-linked polymers and engineered to produce sheet, gel and impregnated dressing formats 21, they contain up to 96 per cent water, thus enhancing the moisture content of necrotic tissue and increasing collagenase production to facilitate autolytic debridement.22

Gels are most effective for debriding but require a secondary dressing to maintain them in situ. This can lead to maceration and excoriation of the wound edges as a result of a wet, rather than moist, environment.11

Hydrogels and hydrocolloids bathe nerve endings thus providing a certain amount of analgesia.

Protease modulators

Biologic dressings composed of either a starch-based matrix, freeze-dried cellulose or collagen or superabsorbent polymers. They act by altering pH to a weak acidic environment or binding proteases with a dressing matrix to remove them from harm's way. Modulators also promote growth factors within the wound bed and have been shown to increase speed of epithelialisation in rats.22

Vacuum-assisted closure (VAC)

Vacuum-assisted closure (a.k.a. topical negative pressure) creates a hypoxic environment in the wound bed, preventing replication and thus survival of aerobic bacteria. Negative pressure removes slough and necrotic tissue and 'pulls’ blood to the wound bed, effecting increased capilliarisation and bringing with it growth factors and macrophages.

Gemeinhardt and Molnars 2005 equine VAC therapy case report indicated it as an effective method for healing large/deep wounds to the body of the horse.23 Reduced scarring is an important aspect of this therapy and must be compared in further research.

Equine survey method, results and discussion

A national postal and e-mail survey of veterinary practices asked participants to fill in a questionnaire to indicate their current wound-care protocols. The return rate was weighted evenly between postal and e-mail returns, with 60 per cent from specialist equine and 40 per cent from mixed practice.

Seventy per cent of respondents used a set collection of products for wound healing; of these, seven out of every 10 reviewed product choice only when new products were put forward for consideration. The remainder either reviewed products quarterly (20%) or annually (10%). 

Moist conditions are a prerequisite for wound healing. However, only 35 per cent of respondents always utilised moist wound healing (MWH) with 65 per cent “sometimes” using it. Established benefits of MWH include reduced scarring and infection, faster healing and increased ease ol debridement; but these were not identified by all practitioners polled (Figure 4).

Figure 5: Dressing types used in practice

Respondents noted that over 60 per cent of owners were unaware of MWH; and of those whose owners were aware, only 40 per cent described owners attitudes to MWH as “sometimes positive” or “positive” overall. This could be related to reports that many vets have issues with owners (or colleagues) removing dressings before wounds are fully healed, so further research into the implications of this in terms of final wound healing time and scarring prevalence would be of interest.

In addition, 65 per cent of respondents stated that they had difficulty keeping dressings in place 20 to 30 per cent of the time, and owners had difficulty on average 40 to 50 per cent of the time. This will further impede progression of MWH in veterinary practice.

When asked to state their preferred debridement methods, a wide variety was reported with 46 per cent preferring surgical debridement.

Better consensus was reported regarding the cleaning of granulating wounds – with vets stating their preferred lavage solution in half of the cases as sterile saline. Water was second favourite (15%) and joint third favourites were iodine (usually Betadine solution) and chlorhexidine gluconate solutions.

More worryingly, other products used were lead acetate and zinc sulphate which, along with other abrasive debridement and lavage applications available, require highlighting owing to their blanket effect which can destroy healthy tissue in the wound bed.

Participants also stated dressing types used (Figure 5) and how they rated their performance. There was clear disparity in the types of wounds treated using each dressing type and in many cases it was possible (hat the user was unaware of the category into w
hich the dressing fitted. An example is foams.

Only one respondent reported using foams in practice; but Allevyn (a foam) was reportedly used in most practices.

A lack of focus on the veterinary community by established product providers appears to have resulted in limited ongoing education of dressings available and their correct usage, including their limitations.

Conclusions and recommendations

Equine wound-care research is conducted in relatively low volumes, mainly comprising case studies. Research recommendations seem slow to transfer into veterinary practice with this survey highlighting that clinicians often choose to continue established protocols and preferred dressing choices for wound healing.

The review* has established potential areas for further study and education, especially in light of treatments proven successful and transposable from human wound care. Further research is recommended to increase awareness of a wider range of products for the benefit of equine wound care.

Case studies to illustrate practical use and experiences, as well as feasibility studies, are needed to assess potential inclusion of recently developed human products in the equine field. There seems to be a requirement for increased independent product and wound healing guidance in veterinary practice. 

A copy of the lull review can be obtained from the author at seanandloniloftus@btinternet.com

Author

Loni Loftus BSc(Hons)

After attending university to study Business Studies. Loni owned and ran a training, livery and competition yard for a number of years She has recently completed a BSc in Equine Science with The Open College of Equine Studies (TOCES) and continues her affiliation by lecturing and marking, as well as managing the online assignment system.

Loni is a freelance trainer focussing on training young horses, in addition to rehabilitation of more experienced horses. As she completed her degree, she developed a particular interest in equine injury, disease, training and rehabilitation and has based much of her project work, including a dissertation, in this field.

To cite this article use either

DOI: 10.1111/j.2045-0648 2011.00085.x or Veterinary Nursing Journal Vol 26 pp 309-312

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Veterinary Nursing Journal • VOL 26 • September 2011 •