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/ The nurse's role in the management of equine limb wounds
The nurse's role in the management of equine limb wounds
Phillippa Pritchard
Monday, March 2, 2015
This article will address the nurse's role in wound management, specifically of the limbs. This will include a quick revision of wound
healing, factors affecting wound healing, types of wounds, dressing limbs and factors to consider when dressing the equine limb. It will
also touch on the differences in healing between horses and ponies and help to relate the factors affecting wound healing to certain
types of wounds.
The nurse's role in the management of equine limb wounds
It is important to note that it is the horse's natural fight or flight instincts that can cause many of the wounds seen in veterinary practice,
whether that be a barbed wire wound from a horse running through a fence or a wound on the distal limb caused by the horse kicking an
object. Equine limb wounds often include an injury to the bone as this is relatively unprotected and therefore exposed to injury (Philips,
1995). Most traumatic wounds are either contaminated or dirty wounds (Southwood, 2008), which will increase the incidence of infection
and this should be noted when dealing with such lesions. In addition, it is important to understand equine wound healing in order to nurse
these patients successfully. It is also important to note the differences in wound healing between ponies and horses and how this may
affect the final outcome of similar wounds in each species. Some tips are included on dressing the equine limb and these are based on the
author's personal experience as an equine veterinary nurse. This article has concentrated on the ability of nurses to improve the outcome
of the patient through thoughtful, critical and holistic dressing of the limb.
Wound healing
A wound is defined as an injury where there is a forcible break in the soft tissues, including open wounds and closed wounds where there is
damage below the surface (Ousten, 2011).
The healing process takes place in three stages (Table 1). The length of each stage will depend on whether wound closure is a viable option;
for example a wound healing via primary intention will take less time to resolve than a wound allowed to heal via secondary intention or
after a delayed primary closure (Ousten, 2011).
Table 1.
Stages of wound healing
Stage of healing
When it
occurs
Haemorrhage,
inflammation and
debridement
In the first
few hours
after insult
What occurs
HaemorrhageClot formationInfiltration of white blood cells (inflammation)Primary
wound contraction
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When it
occurs
Stage of healing
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What occurs
Repair/granulation
12 hours
after insult
New cells produced over the surface of the wound (2 mm/day in a moist wound)After 36
hours fibroblasts and new capillaries are produced forming granulation tissue (bright red
and firm but fragile)This phase is hindered by poor blood supply, necrotic tissue and
debris within the wound
Maturation/scar
formation
From insult
until 2 years
after injury
Open wounds can take weeks to months to heal as these tend to heal via second
intention Surgically closed wounds, i.e. those that have undergone primary closure, heal
via first intention which happens quicker with minimal granulation tissue Tissue regains
strength for up to 2 years, only 80% after the first year
Knottenbelt, 2003; Ousten, 2011
Wound closure occurs via:
!"Primary closure (first intention healing) — a wound closed immediately or after cleaning and debridement, i.e. surgical incision
!"Delayed primary closure — closure is carried out
3–5 days after insult, the delay allows for removal of contamination that would otherwise compromise healing
!"Secondary closure — similar to delayed primary closure but decontamination has taken longer so granulation has started to form
(5–7 days)
!"Secondary intention healing — no closure is attempted and granulation tissue must fill in from the base and edges of the wound
before epithelialisation can occur. This is seen in wounds where the skin deficit is too large or contaminated to suture, or those in
which primary closure has failed. Secondary intention healing relies on the body's own inflammatory response; it prolongs the time
required for healing. As a result scarring is more marked and the cosmetic appearance is worse. For these reasons a veterinary
surgeon may attempt delayed primary or secondary closure (Ousten, 2011).
There are many factors that delay wound healing (Table 2), these factors need to be taken into account by all involved in wound
management in order to achieve a successful outcome.
Table 2.
Factors affecting wound healing
Factor
Reason for delay
Infection
Good hygiene and cleaning of the wound initially can reduce the incidence of further infection. If a wound becomes
infected the patient may show signs of systemic infection such as anorexia and pyrexia, the wound itself will look red,
swollen, discharge may be seen with a odorous smell and the patient will be uncomfortable at the site
Movement
Movement at the site or of attached tissues delays healing, excessive mobility disrupts capillary beds and can cause a
chronic inflammatory status within the wound. Lack of all movement can also be counter productive as it causes
poor arrangement of the collagen fibres causing weaker healing
Foreign body
The most common reason for non-healing wounds; can include sand/grit particles, wood/plant matter, necrotic
tissue, suture material and even hair from clipping around the wound
Necrotic
tissue
Necrotic tissue retards healing. Tendon and bone are slow to exhibit non-viability and so careful debridement prior
to closure is beneficial
Altered pH
Certain bacteria can alter the pH of the wound; the site should be at normal physiological pH or slightly acidic
Blood supply
Poor blood supply for example due to disruption of a blood vessel can cause reduced oxygen supply to healing
tissues. Some areas such as the dorsal hock are thought to have a naturally poorer blood supply
Impaired
oxygen supply
Lowered systemic oxygen concentration due to decreased blood flow or anaemia slows wound healing and increases
inflammation
Poor nutrition
or health
Older horses heal slower than the young; hypoalbuminaemia suppresses healing and encourages inflammation
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Factor
Reason for delay
Local factors
Wounds with a pouch of skin or excessive dead space can fail to heal. Accumulated fluids can be an ideal medium for
bacteria. Self trauma localised to the wound will obviously slow or prevent healing
Iatrogenic
factors
Incisions, swabbing, use of forceps and retractors can all cause localised injury to tissues, sutures can act as foreign
bodies, excessive pressure can compromise blood supply and use of corticosteroids suppresses wound contraction
Genetic
factors
Large horses heal less well than ponies, horses with congenitally weakened skin are more easily traumatised
Knottenbelt, 2003. Points highlighted in red are those that nurses should be aware of when managing a wound on a limb
Factors that concern the veterinary nurse
The factors highlighted in Table 2 are those that nurses should be aware of and that can be minimised and acted on to achieve the best
outcome. It will never be possible to remove every factor that delays wound healing but nurses should do everything they can to aid healing
by reducing the effect of these factors. A wound involving a synovial structure that has not been identified may also affect wound healing
and also the overall prognosis of the patient; it has been suggested that 17% of heel lacerations involve such a structure (Southwood,
2008), so initial examination by the clinician is very important.
Good hygiene
In order to ensure infection is not introduced into the wound good hygiene is of paramount importance. Gloves should always be worn
when examining the patient and changed for each patient in order to help reduce infection, and this must be enforced for all those
examining the wound. Passing an infection such as MRSA to a patient is an all too real possibility; it is known that humans contribute to the
spread of infection (van Duijkeren et al, 2010).
Cleaning of the wound
A heavily contaminated wound should be flushed thoroughly using sterile saline, a syringe and an 18-gauge needle this combination
produces the correct pressure for flushing contaminated wounds (Ousten, 2011). Disinfectant can be used but with caution: if it is too
concentrated it becomes toxic to fibroblasts and other cells involved in wound healing (Phillips, 1995). It is advised to use disinfectants in
concentrations that maintain antibacterial efficacy while minimising the risk of toxicity to cells, Phillips (1995) suggests 0.1% iodine and
0.05% chlorohexidine as adequate.
Hair from clipping around the wound
It is a very simple task to protect the wound before clipping to prevent further contamination; even if the wound is already contaminated it
is not beneficial to add more contaminants. The use of hydrogel Intrasite Gel (Smith & Nephew) (Figure 1) or KY jelly applied into the
wound will prevent hair from entering the wound during the clipping process. The contents of an unopened tube of both products is sterile
and therefore will not introduce further contamination. However it is important to clean this gel away thoroughly before further
investigation by the veterinary surgeon.
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Figure 1. Note the Intrasite Gel visible, especially medially, on this wire wound to the forearm, to prevent contamination during clipping.
Self trauma
Self trauma may be more common in wounds to the body than the limbs, and an element of self trauma may still be evident when wounds
are dressed. The temperament of some horses means they are not going to tolerate a dressing well. Youngstock in particular tend to
struggle, they can be found pulling chunks out of their dressings while lying down (personal experience). Cribbox (hydrophane) can be used
to aid in discouraging them from destroying the dressing; it is soul destroying to spend an hour placing a dressing only for the horse to
destroy it in minutes. Distraction can also be used such as walking the horse when the dressing is new on (dependent on the wound or
dressing type), snack balls, company (human or horse), tying them up for a period after the initial application and the use of bibs or a neck
cradle (Figure 2). If all else fails, sedation, usually acepromazine so feeding can still continue, may play a part in discouraging this destructive
behaviour until the new dressing has been ‘worn in’.
Figure 2. An example of a bib used to prevent self trauma in the horse with the forearm wound shown above. Note the food in the bib
meaning the patient is still able to eat normally while the bib is in place.
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An underestimated area with respect to self trauma is consistency in the person placing the dressing. Everyone does dressings differently
so if a patient has been unsettled in one person's dressing but much better with another person's then continuing with the preferred person
will help to prevent stress in the patient and a large bill for the client.
Excessive pressure can compromise blood supply
Excessive pressure can occur throughout the dressed area or in specific areas, the most common places that suffer from uneven pressure
when dressed are shown in Figures 3 and 4. The red markers on the horses' legs show soft tissue areas that are affected by inappropriate
pressure and the white marks are bony prominences that are commonly affected (personal experience). The areas the horse develops
pressure sores depends on the conformation of the limb, some horses have very straight legs whereas others have relatively large,
prominent joints. Veterinary nurses should be aware of the conformation of the patient's limbs and dress the limb in a holistic fashion; that
is dress each leg as an individual, no two legs will be dressed the same. There are ways of minimising the damage for example: if a leg has a
particularly prominent medial malleolus or if a horse has a pressure sore on its fetlock on admission, then additional padding can be added.
If a pressure sore is evident on a dressing change it is important to adjust the dressing accordingly, not just replace the dressing as it was
and hope for the best. Care should be taken not to make a dressing too tight as this could cause a horse to self traumatise — check the
tension of the dressing numerous times throughout placement not just at the end.
Figure 3. Areas affected by inappropriate pressure through a dressing in the forelimbs.
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Figure 4. Areas affected by inappropriate pressure through a dressing in the hindlimbs.
Movement
Movement is a problem in horses — it is difficult to get a horse to stay still, and any movement can result in the dressing sliping or the
wound reopening — and dressings play a large part in minimising this movement. If the fetlock needs to have minimal flexion then the
dressing needs to aim to stop this movement, if there is a dorsal hock wound then the aim is to reduce flexion of the hock. Ultimately the
size of the dressing is down to the veterinary surgeon; the more layers they ask for then the more they wish to stop movement, i.e. a four
layer full limb dressing will ensure the hock does not flex. The horse in Figures 5 and 6 had bone chips removed from her fetlock at surgery
so a four layer dressing was applied to minimise movement of the joint.
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Figure 5. Note the reddening of the skin on this white Thoroughbred limb, this requires careful monitoring at each dressing change and
padding where necessary.
Figure 6. The same wound as seen in Figure 7 with a four layer dressing in place.
Dressing the equine limb
The factors detailed above should be in the forefront of every nurse's mind when dressing a wound. The primary dressing will be decided by
the clinician involved in the case but will usually be a non-adherent absorbent dressing, such as Melolin (Smith & Nephew) or a
hydrocellular foam dressing such as Allevyn (Smith & Nephew), Tielle (Johnson and Johnson), depending on the amount of exudate. Some
wounds may require other dressings, such as a manuka honey dressing, to aid in removal of contaminants from the wound (e.g. Kruuse
Manuka honey dressing or Activon, Advancis Medical). Honey is known for its antimicrobial properties even after dilution and is effective
against common wound pathogens, such as Escherichia coli, Pseudomonas spp. and meticillin-resistant Staphylococcus aureus (MRSA)
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(Carnwath et al, 2014).
At the author's clinic honey is commonly used for contaminated heel bulb wounds to aid in reduction of bacterial load of the wound prior to
a foot cast being placed, such as that seen in Figures 7 and 8.
Figure 7. An example of a heel bulb wound that has a high chance of contamination, i.e. a candidate for Manuka honey application.
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Figure 8. The same wound as seen in Figure 7 with a foot cast in place.
How to protect the compromised areas
There are a number of ways to further protect areas of damaged/compromised skin and these can be as simple as applying a foam dressing
to reddened skin; a foam dressing is ideal as it provides the covered area with a bit of padding to help to relieve soreness. Other materials
that are commonly used to prevent or relieve pressure sores at the author's clinic are Soffban (BSN) and orthopaedic felt. Soffban has
proved invaluable to the author's clinic when dressing limbs; ‘sausages’ are made out of it and used to the take pressure off compromised
tendons and the orthopaedic felt is used if a patient has a particularly bad sore, such as ulcerated skin over bony prominences like the
accessory carpal bone. The thickness of the felt allows the limb to be dressed for the original problem while at the same time preventing
further damage to the bony prominence. Cutting a hole in the felt and placing a foam pad over the top to absorb any exudate from sores
completely removes any pressure to the area and allows healing to occur. It is important to remember that both of these methods will
change the shape of the leg that is to be re-dressed, so that extra padding will be needed. The author finds that padding out the narrow
areas first (for example the pastern and the cannon) enables application of the first layer of cotton wool across the whole area to be
dressed, achieving a functional and aesthetically pleasing dressing. Using 15 cm of conforming bandages may give a much more even
pressure through the dressing than 10 cm, so the author uses the large 15 cm roles for all but the smallest of patients.
Robert Jones bandages (RJB) and casts
RJB and casts are used to completely immobilise an area, i.e. where there is a fracture or a large wound. The RJB at the author's clinic are
only changed every 10 days unless something indicates a premature change is warranted, e.g. strike through or excessive lameness. Casts
can be kept on for a number of weeks and can be a more cost-effective method of immobilisation than a RJB. As casts remain in place for a
such a length of time it is exceptionally important to provide enough padding to delicate areas to prevent pressure sores. Bony
prominences should be well padded and any compromised tendons should have pressure relieved where possible, it is not an easy or cheap
job to change a cast if a problem occurs, so it is in everyone's best interest to do a good job the first time around.
Ponies versus horses
It is well documented that ponies heal better and more quickly than horses and there appear to be a number of reasons for this (Wilmink et
al, 1999). There seems to be a higher rate of successful first intention healing in ponies, this is due to a more effective acute inflammatory
response leading to reduced wound infection rates. Second intention healing also appears to occur faster in ponies due to a weak and slow
onset inflammatory response in the horse. Horses are more prone to exuberant granulation tissue (also because of this weak inflammatory
response) and this also persists over time causing a chronic inflammatory state (Lepage, 2011) delaying wound healing.
Conclusion
In summary, the veterinary nurse's role in wound healing is very much a supportive and preventative one. Veterinary nurses should be
aware of how wounds heal but more importantly they should be aware of factors detrimental to healing and ways to minimise these
factors. Good hygiene and prompt recognition of pressure sores are an extremely important part of the veterinary nurse's role and should
always be in the forefront of their mind when dressing the equine limb. It should never be assumed that heavier breeds have tougher skin,
as this is not always the case, and finally nurses should be critical about the dressings they have applied. The more critical a nurse is of the
dressings applied the more they will strive to improve their work the next time.
Key Points
!"A knowledge of the factors that affect wound healing enables the equine veterinary nurse to dress a limb in such that promotes
healing.
!"The skin on horse's limbs is very mobile so if a limb is not sufficiently immobilised some wounds may fail to heal adequately or
produce exuberant granulation tissue which requires further veterinary intervention.
!"Protecting areas that have become compromised due to long-term dressing of the limb is key to preventing pressure sores becoming
such that the skin is ulcerated and therefore painful for the patient.
!"Dressings that are placed beneath cast material require careful padding to protect the bony areas that are very evident in the equine
limb, adequate padding should prevent pressure sores and potentially premature removal of a cast.
!"Horses do not always cope with dressings on limbs, signs of distress and apparent non weight bearing lameness in the stable may be
due to a patient's dislike of a dressing and it is worth considering the dressing as a cause of distress in cases where limbs are
restricted.
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