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Wound bed preparation is a phrase that was coinedover a decade ago (Falanga, 2001) to describe theprocess of effective cleansing and sympatheticdebridement that helps a wound achieve healthy,rapid granulation for closure. The bioburden ofdebris and devitalised tissue in all traumatic woundsnot only delays healing by prolonging theinflammatory response (Midwood et al.,) but alsorisks infection and expensive complications. It isclear then that the process of cleansing to removeheavy contamination and reduce subsequentinfection risk is an essential task.

All modern clinicians understand the importance ofwound cleansing to reduce infection risk, but tomany it is an area of controversy and contradiction.Clinicians in practice can not be blamed for beingoverwhelmed by the research and on that basispractice has become more habitual than evidencebased (Evans et al., 2009).

REMOVAL OF BIOBURDEN

Bioburden is the debris in the wound that acts as afocal point for bacterial proliferation, a source ofwound infection and foreign body reactions. Left in situ it prevents formation of healthy granulation by delaying the processes that stimulate angiogenesis.

The result is healing delay. To see this effect in actionwe only have to observe what happens when suturematerial fails to dissolve as expected (Figs. 2a and 2b).

Despite the best intentions, even the mostsophisticated wound dressings available requiresympathetic wound preparation and removal ofbioburden to be of any benefit (Falanga, 2000) andalthough the wound may not exhibit signs of

Georgie Hollis BScSECRETARY OF THE VETERINARY WOUND HEALING ASSOCIATION AND FOUNDER OF THE VETERINARY WOUND LIBRARYwww.vetwoundlibrary.co.uk

Wound cleansing: Have we learned anything?

ABSTRACT: Wound cleansing has been practised for centuries and despite our advances in the medical fieldthere is still much confusion about which solution to use for cleansing wounds in practice. From boiled waterto cytotoxic chemicals the annihilation of bacteria has become our biggest obsession but it should not be at theexpense of the healing process. As multi-resistant organisms begin to reduce our options for antibiotic use itappears that dilution remains the solution to pollution. DOI: 10.1111/j.2044-3862.2012.00188.x

Fig. 1: Bioburden: the mass of slough, debris and contamination that contributesto infection risk.

Fig. 2a: Bioburden can be seen as a prolonged inflammatory response andfailure to heal.

Fig. 2b: Once the remaining vicryl suture was removed from the woundhealing progressed rapidly.

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now used as a very general term to describe anytissue that is slightly unpleasant, and as such misleadsprofessionals and animal owners alike. Wrongly usedas a description for normal inflammatory exudateand slough the temptation is to assume the worst andhinder the healing process with the most potent,cytotoxic antiseptic available.

As the medical profession has been a largely privateaffair until the birth of the NHS the recipes thatpassed down from generations were integrated intopotions, lotions and remedies that remain profitablein the private market. Many make impossible claimsto speed up healing and banish symptoms such asodour (of which foul odour is a clear sign ofinfection), inflammation (a natural process ofhealing, or a sign of infection) and pain. Althoughour modern medical device regulations and theEuropean CE marking system will give someconfidence that a product is credible for medical use,verification is not required for wound managementproducts in animals. As long as a product makes nomedicinal claims it may be marketed freely forclinical use (Defra website). Increasingly elaborateand convincing marketing appeals to ourresponsibility when dealing with wounds and thefear of infection remains. The development ofantibiotic resistance in healthcare also makes thesearch for a safe, universal solution for preventinginfection commercially irresistible.

A focus on the use of products with ‘natural’ingredients appeals to our modern, eco-friendly,healthy approach (clearly the case in the equinehealthcare market) but this does not mean cytoxicityis avoided. The use of Tea Tree oil is a typicalexample. Proven as antimicrobial and anti-inflammatory if used at high concentrations it can beboth cytotoxic and irritant, furthermore, whenexposed to air and light, some of its 100 or socomponents oxidise to further potentiate this effect(Russell, 1999). Frivolous application will be antiseptic,but at the cost of wound healing if not carefullydiluted (Federal Institute for Risk Assessment, 2003).

WHAT IS THE IDEAL SOLUTION?

The modern use of antiseptics and antimicrobials forwound lavage is met with contradictions both inresearch and opinion and despite many thoroughreviews a definitive recipe using a single solution isnot forthcoming.

As healing relies upon an unhindered progressionthrough inflammation to enable proliferation andthe formation of healthy granulation tissue it islogical that we should choose a product that does noharm. Any choice we make must weigh up the riskthat products intended to kill pathogens may alsocompromise the cycle of healing.

Chlorhexidine and povidone iodine are the mostcommon antiseptics in daily use for open wound

infection, a heavy bioburden will prolong theexudative inflammatory phase meaning the clientand patient are likely to need to attend more visitsover a longer period.

A HISTORICAL PERSPECTIVE

As far back as history goes methods for woundmanagement and relative improvements have beendescribed (Majno, 1975). What we may think of as amodern evidence based approach in the area ofwound lavage was actually being considered morethan 300 years BC. Hippocrates and later Galenaround 150 BC had a very limited knowledge ofmicrobiology but amongst their solutions forcleansing (which included wine and beer) theyconcluded that the use of boiled water showedimproved outcomes to unboiled water.

BACK TO THE DARK AGES: CLEANSING WOUNDS

FROM THE SENSIBLE TO THE DOWN RIGHT

RIDICULOUS

Although Hippocrates and Galen agreed over manyprinciples they ultimately appeared to contradicteach other. Hippocrates believed in washing thewound and performing debridement to removesuppuration, but being a more modern man, Galenproposed that pus was actually beneficial. Hewitnessed that when pus appeared the wound wouldheal shortly afterwards. The theory of ‘laudable pus’developed and the wounds were effectivelyencouraged to suppurate in an effort to encouragehealthy angiogenesis and vascularisation of thewound bed (Serham, 2011).

Over centuries home-made methods of woundmanagement developed. Each farmer added his ownrecipe and those that appeared to be successful werehanded down from father to son. Wounds werewashed with solutions such as warm ox urine,vinegar and wine (Forrest, 1982) and dressed withpoultices to encourage suppuration or to ‘bring outthe infection’. Although a positive influence wouldhave been achieved through the natural debridementprocess many of the topical methods developed weresimply intended to prolong the inflammatoryresponse through foreign body or cytotoxic effects.

We may think that we are beyond these times, but insome circles, even in the UK, these outdatedprinciples that prolong inflammation and delayhealing are still being held. A recent trend seesanecdotal uses of menthol based muscle warmingproducts on and around open wounds on horses. Thehistorical belief prevails that this will ‘bring outinfection’ and speed healing.

Joseph Lister in the late 1800s first linked theformation of pus with infection during a periodwhere mortality from infection was high. He beganwhat is the incorrect assumption that the generalpresence of pus is a sign that infection is present(Toledo-Pereyra & Toledo, 1976). The word pus is

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management. At the correct dilution (0.05% and 0.1- 0.5% respectively) will have an antimicrobial effectthat will be helpful in reducing bacterial burdenwithin high risk, heavily contaminated wounds(Drosou et al., 2003). Neither of these products isperfect in terms of their cytotoxic profile, butchlorhexidine has been found to be more effectivethan povidone iodine or saline for lavage in theveterinary patient (Sanches et al., 1988). Despiteantimicrobial efficacy, their use does not substitute areduction in physical bioburden through thorough,correct lavage using a physiological solution (Salamiet al., Khan & Naqvi, 2006) (Table 1).

The use of antiseptics should also be consideredagainst recent research into the positive role thatbacteria play in wound healing and in light ofincreasing numbers of resistant strains. There appearsto be growing evidence to suggest that a completelysterile wound is at a disadvantage (Inflammation andWound Healing, 2004), supporting the concept thatphysical removal to a level below the threshold forinfection (around 105 bacteria per cm2 dependingupon virulence) is our goal. Removal of excessivebacterial burden rather than complete annihilationusing a toxic solution would appear to be thepreferential approach (Buffa et al., 1997).

The use of tap water is controversial as hypotonicity,minerals and low pH make it unpopular as a choice

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of lavage solution in veterinary practice. Its efficacyand cost effectiveness means it is regularly used inhuman healthcare. If no other solution is available itsuse will be more beneficial than detrimental(Whaley, 2004).

An animal owner or clinician using tap water earlyin the lifetime of a wound will still reduce the riskof infection exponentially for every hour earlier the wound is cleansed. An animal owner able tothoroughly (and safely) lavage a wound using tapwater will be able to reduce the risk of infection significantly the earlier it is performed after injury(Fig. 3). This process alone will do more to reduceinfection rates than any antiseptic or antibioticapplied hours later (Owens & Wenke, 2007).

ADDING SURFACTANTS

A mild detergent in the form of a non-cytotoxicsurfactant with a lavage solution may be used to assistin gentle softening and removal of proteinaceous andstubborn fibrous slough. Enabling a greaterreduction in volume of bacteria in the woundcombined with an antiseptic effect, their use canassist debridement of fragile and complex wounds where lavage alone may not be enough(Anglen, 2001).

Surfactant properties are of increasing interest as theymay help to remove problem bacterial biofilms that

Acceptable cleansing Usage Cytotoxic Practical considerations

solutions considerations

Povidone iodine 0.1-0.5% dilution for Conflicting research shows Over 0.7% iodine actuallymanagement of heavy variable levels of cytotoxicity lowers iodine availability ascontamination, and including detrimental effects it binds more readily to theknown bacterial on capillary density (Peter, carrier molecules.colonisation including & Li-Peuser, 2002). Iodine is deactivated by multi-resistant species. surface proteins and may be

less effective than expected in heavily contaminated wounds.

Chlorhexidine gluconate 0.02-0.05% dilution for Normal concentrations are Residual effect lasts for sixmanagement of heavy toxic to tissue fibroblasts hours. contamination, and in vitro, although not known bacterial observed in vivo. Inhibited by detergents andcolonisation including will precipitate in saline.multi-resistant species.

Hartmann’s, lactated The ideal lavage solution Non cytotoxic. Solution must be at theRingers solution or for all wounds being correct pressure, volume,buffered physiological most sympathetic to temperature (Table 2).saline cells and physiology.

Physiological saline Most common lavage Mildly cytotoxic to canine pH contributes to cytotoxic (0.9%) solution for open fibroblasts after 10 minutes effect.

wounds. in vitro.

Tap water Readily available and Significant cytotoxic effects Early use within hours of accessible. on canine fibroblasts in vitro. injury may be justified to

achieve significant reduction in bioburden before proliferative phase of healing.

TABLE 1: The most commonly used solutions and their use

have been identified as being of potentialeconomical significance in human wounds. Biofilmsare effectively summarised as colonies of what may be complementary and potentially pathogenicmicrobes that produce a protective protein coatwhich helps them to survive our antiseptic andantibiotic assaults (Serralta et al., 2001).Unfortunately these colonies are hard to see in thewound and can only be assumed based on symptomssuch as failure to heal and repeated colonisation orinfection despite selective antibiotic use.

CONCLUSION

The availability of antimicrobials in practice does notmean they should be used in every wound, highvolume use of a balanced electrolyte solution(Hartmann’s or lactated Ringer’s solution) at the rightvolume, pressure and temperature (Table 2) is likelyto be the best option for washing most wounds.

Correct, early lavage can not be underestimated in itspotential to improve wound healing. Combined withsympathetic debridement, it is the crucial step whichturns a potentially catastrophic wound into onewhich can be closed in as quick a time as possible.

Faith in older treatments and the lure of clevermarketing will challenge what owners (andclinicians) choose to use on wounds to help themheal. Ointments and lotions may simply hide whatare in reality outdated ingredients. Boric acid(e.g.Wound powder), lead acetate, Dakins Solution(Bleach), and hydrogen peroxide are readily availableand when recommended by friends, colleagues andindustry it is hard to take the simple approach.

Evidence is plentiful that to achieve a healthy,healing wound, a reduction in bioburden is the key.Ingredients that add to this bioburden (or claim toavoid the need to reduce it!) will either delay healing

© 2012 Blackwell Publishing Ltd

Fig. 3: Tap water has its place.

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or at best have no benefit over simple high volumelavage with normal saline.

Our fear of infection is our greatest enemy as it hasbeen throughout the centuries. But as Hippocratesrealised, it is better to wash a wound and remove thesuppuration than to allow infection to form. Perhapsits time to go back to basics.

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BUFFA, E. A., LUBBE, A. M., VERSTRAETE, F. J. M. and SWAIM, S. F.

(1997), The Effects of Wound Lavage Solutions on Canine Fibroblasts:

An In Vitro Study. Veterinary Surgery, 26: 460–466.

DROSOU. A., FALABELLA, A., KIRSNER, R. Antiseptics on Wounds:

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EVANS, L. K., KNOWLES, T. G., WERRETT, G., HOLT P. E. J Small Anim

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FALANGA, V. Classifications for wound bed preparation and

stimulation of chronic wounds. Wound Repair Regen 2000; 8(5): 347-52.

FALANGA, V. Introducing the concept of wound bed preparation. Int

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undiluted tea-tree oil as a cosmetic. Opinion of the Federal Insitute

for Risk Assessment (BfR), 1 September 2003.

FLETCHER, J. (1997) Update: wound cleansing. Professional Nurse;12:

11, 793-796

FORREST, M. B. Early history of wound treatment. Journal of the Royal

Society of Medicine Volume 75 March 1982.

GABRIEL, A., SCHRAGA. Wound Irrigation. Medscape. Updated May

19 2011. http://emedicine.medscape.com/article/1895071-overview.

INFLAMMATION AND WOUND HEALING: The Role of Bacteria in

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KHAN, M. N., NAQVI, A. H. Antiseptics, iodine, povidone iodine and

traumatic wound cleansing. J Tissue Viability. 2006 Nov;16(4):6-10.

MAJNO, G. The Healing Hand – Man and wound in the ancient world.

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MIDWOOD, K. S. WILLIAMS L. V. et al., Tissue repair and the dynamics

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OWENS, B. D., WENKE, J. C. Early wound irrigation improves the

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PETER, F. W., LI-PEUSER H. Clinical and Experimental Dermatology,

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RUSSELL, M. 1999. Toxicology of tea tree oil, p. 191-201. In I. Southwell

and R. Lowe (ed.), Tea tree: the genus Melaleuca, vol. 9. Harwood

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SALAMI, A. IMOSEMI, I. O.and OWOEYE O. A comparison of the

effect of chlorhexidine, tap water and normal saline on healing

wounds. Int. J. Morphol., 24(4):673-676, 200

SANCHES I. R., SWAIM S. F., et al., (1988), Effects of Chlorhexidine

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http://www.vmd.defra.gov.uk/pharm/non-med.aspxº

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Volume of solution ‘Dilution is the solution to pollution’ as they say. Forfeit of volume in favour of antimicrobial potency will likely cost more and achieve less in reducing bioburden. Correct lavage volume is between 50 and 100 mls per 1 cm2 of (or cm length for lacerations) (Gabriel & Schraga, 2011).

Pressure of application The optimum pressure of application of lavage solution to be 8-15 pounds per squareinch. This is achieved in practice through a 19-20 gauge needle attached to an infusionbag. 250 ml cans of saline designed to provide saline at this pressure are available (Aquaspray from Animalcare Ltd). A one-way valve avoids cross contamination back into the can. Although 250 ml is not enough volume for most wounds on first presentation they are useful as a cleanser between dressing changes or for home use.

Temperature Ideally all lavage solutions should be used at between 37 and 42°C. A wound will take up to 40 minutes to reach body temperature after cold irrigation and up to three hours for leukocyte activity to recover (Fletcher, 1997).

Timing For every hour earlier a wound is lavaged the risk of infection will be significantly reduced. It may be better to lavage a wound thoroughly with tap water early than to wait until the ideal physiological solution is available.

TABLE 2: It’s what you do with it that counts!

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