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Wound bed preparation: a proactive treatment

Deirdre Thompson
RGN
Senior Tissue Viability Nurse Specialist
Heatherwood and Wexham Park Hospital NHS Trust
Wexham Park Hospital
Slough
E:deirdre.thompson@hwph-tr.nhs.uk

The basic principles of the ideal wound dressing have not changed since the publication of Winters' research on moist wound healing.(1)
Recently there has been much written about wound bed preparation. It has been defined as "the desire to provide an optimal environment by producing a stable wound bed with minimal exudate"(2) and "the acceleration of endogenous healing to facilitate the effectiveness of other therapeutic measures".(3) Wound bed preparation links treatments to the cause of the wound by focusing on four components, namely:(4,5)

  • Debridement.
  • Decreasing bacterial burden.
  • Moisture balance.
  • Control of oedema.

Before deciding on local wound management options, the practitioner must first identify the potential factors causing any disruption to the healing process and take appropriate action. The focus should be proactive rather then reactive, as is often seen in symptom control. Proactive wound management considers the control of symptoms before or as they occur, rather than simply managing them.(4) An example of proactive wound management in malodorous and heavily exuding wounds would be the treatment of the cause, which is often an underlying infection. Wound bed preparation should be considered for chronic wounds that are not progressing as normal, and the overall management aim should be to achieve a stable wound - characterised by a well- vascularised, moist wound bed with minimal exudate.(6)

Debridement
Debridement is the term used to describe any method that facilitates the removal of devitalised tissue, cell debris or foreign bodies from a wound. The National Institute for Clinical Excellence (NICE) states that "debridement is an accepted principle of good wound care, especially when debris is acting as a focus of infection".(7) The main methods of debridement are:(8,9)

  • Autolytic.
  • Enzymatic.
  • Mechanical.
  • Sharp debridement.
  • Surgical debridement.
  • Biosurgical.

Autolytic
The main dressing products used to promote autolysis are hydrogels, hydrocolloids and hydrofibre dressings.

Hydrogels
Hydrogels come in two formulations, either as a gel or as a flat sheet. They have a high water content combined with starch and a preservative. Differences in the gel composition are responsible for the variations in fluid-donating ability, which can have an inverse effect on the gel's ability to absorb fluid, hence a balance is required.(8)
Products: Aquaform (Unomedical), ClearSite (ConMed), Geliperm (Geistlich Sons), Granugel (Convatec), Hydrosorb Plus (Paul Hartmann), Hypergel (Mölnlycke), IntraSite Gel (Smith & Nephew), IntraSite Conformable, Nu-Gel (Johnson & Johnson), Opragel (Lohmann), Primskin (Spenco Healthcare), Purilon (Coloplast), Spenco 2nd Skin (Spenco Healthcare), Sterigel (Seton), Vigilon (Bard), Suprasorb G (Venon-Carus), Normagel (Mölnlycke) and Novogel (Ford).(10)

Hydrocolloids
Hydrocolloid is the term used to describe wound management products containing gel-forming agents such as sodium carboxymethycellulose and gelatin, and are usually combined with elastomers and an adhesive matrix and applied to a carrier. In the presence of exudate the adhesive mass absorbs fluid and forms a gel. Some dressings form a cohesive gel, while others are hydrophilic (ie, form a more mobile, less viscous gel).(9)
Products: Askina Biofilm Transparent (Clinimed), CombiDERM (Convatec), the Comfeel range (Coloplast), the Granuflex range (Convatec), Suprasorb H (Vernon-Carus Ltd), Tegasorb (3M Healthcare), Replicare Ultra (Smith and Nephew), Hydrocoll (Paul Hartmann), Varihesive (Convatec), Ultec Pro (Kendall).(10)

Hydrofibre dressings
Hydrofibre dressings are highly absorbent, nonwoven sheets or ribbon composed entirely of hydrocolloid fibres. On contact with fluid the dry dressing converts to a soft gel that absorbs moisture and debris effectively. The dressing assists in autolysis and promotes angiogenesis or the revascularisation of the wound bed.
Products: Aquacel (Convatec).(10)

Enzymatic
Currently there is only one licensed enzyme preparation available in the UK - Varidase Topical (Wyeth Pharmaceuticals). It contains two enzymes: streptokinase, which dissolves fibrin, and streptodornase, which liquefies pus cells. A small study comparing Varidase with a hydrogel showed a faster removal of eschar with the hydrogel patient group.(11)

Mechanical
Mechanical debridement can take the form of high-pressure irrigation, whirlpool and compression therapy. High-pressure irrigation involves the use of high-pressure jets of water or saline directed at the wound to loosen debris and remove bacteria. Whirlpool therapy involves immersing the wound in large pools of water, allowing the turbulence to separate the dead tissue. The above methods are rarely used in the UK, as appropriate equipment is not available to prevent splashback and maintain adequate infection control measures.(12)

Sharp debridement/surgical debridement
Sharp debridement is the removal of dead or foreign material just above the level of viable tissue, and is carried out without anaesthetic by a doctor or nurse.(13) Surgical debridement involves the excision or wide resection of necrotic tissue, often removing viable tissue from wound margins, and is carried out by a surgeon in theatre.(14) Sharp debridement provides a fast and effective method of wound debridement, but the practitioner must have the knowledge and ability to safely carry out the procedure, be aware of underlying anatomical structures, and stop if he/she becomes uncomfortable, uneasy or uncertain at any time during the procedure.(15)

Biosurgery
Maggots are living chemical factories that move over the surface of a wound and secrete powerful enzymes. The enzymes breakdown dead tissue, turning it into liquid, which the maggots then ingest. Maggots also prevent the growth of microorganisms by ingesting bacteria and changing the pH of the wound to 8-8.5, which inhibits the growth of some bacteria.(16-18)
Products: LarvE, BioBag. LarvE are "free range" - that is, they move freely over the wound bed and are removed after 2-3 days. BioBag contains the maggots within a sterile net bag that is removed after 5-7 days.(10)

Decreasing the bacterial burden
Decreasing the bacterial burden in colonised wounds will prevent the wound from becoming critically colonised or, indeed, infected and prepare the wound bed for healing. Appropriate interventions include debridement of devitalised tissue and biosurgery, as discussed above, use of interactive antimicrobial wound dressings and use of topical negative-pressure or vacuum-assisted closure therapy.

Interactive antimicrobial dressings

Cadexomer dressings
Cadexomer dressings contain hydrophilic beads impregnated with iodine. Following contact with wound fluid, the beads absorb excess moisture, while at the same time releasing iodine into the wound bed. This provides effective treatment for infected, sloughy wounds and assists in the prevention of infection.(19)
Products: Iodosorb and Iodoflex (Smith & Nephew).(19)

Inadine
Inadine, on the other hand, is a topical wound dressing impregnated with an ointment containing 10% povidone iodine. The dressing provides a long-lasting antiseptic effect that assists in the prevention of infection by bacteria and protozoal and fungal organisms.(10)

Silver-impregnated products
Metallic silver and its salts have antibacterial properties -  they bind with the DNA of the bacteria, which then impairs cell reproduction.(10) Silver is widely recognised as an effective broad-spectrum antimicrobial and has been integrated into various medical devices and wound care products. The bactericidal potency of silver-impregnated dressings appears directly proportional to the amount of free silver ions released into the wound bed.(20)
Products: Acticoat and Acticoat 7 (Smith & Nephew), Actisorb Silver 220 (Johnson & Johnson), Aquacel Ag (Convatec), Contreet (Coloplast), Advance (SSL International), Flamazine (Smith & Nephew).

Topical negative-pressure/vacuum-assisted closure therapy
Topical negative-pressure or vacuum-assisted closure (VAC) applies localised subatmospheric negative pressure to a wound bed via a computerised therapy unit. It assists in the removal of excessive levels of exudate, reduces oedema, improves the microcirculation, stimulates granulation tissue formation and wound contraction, and reduces the bacterial loading of the wound bed.(21)

Moisture balance
Another element of wound bed preparation is the maintenance of moisture balance. Chronic wound exudate differs from that of acute wounds, as it has altered levels of proteases and their inhibitors, resulting in fluid that can be corrosive in nature. Although moist wound healing is an accepted concept in wound management, there must be a balance between a wound being either too wet or too dry.(4) This balance can be achieved by the use of modern wound management products, graduated compression therapy and VAC therapy as discussed previously.

Foam dressings
Foams assist in the maintenance of a balanced moist wound environment by absorbing large amounts of exudate. The materials used in foam dressing are vapour-permeable, allowing the fluid to evaporate.
Products: Allevyn range (Smith & Nephew), Advance (SSL International), Biatain range (Coloplast), Cavi-care range (Smith & Nephew), Flexipore (Polymedica), Lyofoam and Lyosheet (Seton), the Tielle range (Johnson & Johnson), Transorbent and Truform (Unomedical).(10)

Hydrocapillary and capillary dressings
Hydrocapillary and capillary dressings are used to absorb and manage large amounts of exudate. They generally consist of two or more layers of material and features found in other dressings. They are designed for low- to high-exuding wounds, generally combine all features of a film, a foam and a hydrogel to create a self-adhesive, absorbent dressing, thus providing a moist wound healing environment, and an outer waterproof layer allowing moisture evaporation while also protecting against external contamination. These are sometimes described as "intelligent" dressings.
Products: Alione (Coloplast), Transorbent (Unomedical), Vacutex (Protex), Versiva (Convatec).

Control of oedema
Compression therapy, when used appropriately, can assist in reversing venous hypertension, reduce oedema and provide a warm, moist wound healing environment that can lead to softening and separation of slough and increase vascularity to the wound bed, thereby improving wound healing rates.(12) Before deciding on the appropriateness of compression therapy, a full vascular assessment should be undertaken. A range of techniques are available such as ankle brachial pressure index, segmental volume plethysmography/pulse volume recording, and ­transcutaneous oximetry.(4)

Conclusion
This article has examined the various methods of wound bed preparation available to the practitioner, focusing on the four components of debridement, decreasing bacterial burden, moisture balance and oedema control. Wound bed preparation should be linked to the cause of the wound and/or the cause of the delay in healing, and treatment should be proactive as opposed to reactive.

References

  1. Winters GD. Formation of the scab and the rate of epithelialisation of superficial wounds in the skin of a young domestic pig. Nature 1962;193:293-4.
  2. Dowsett C. The role of the nurse in wound bed preparation. Nurs Stand 2002;16:69-76.
  3. Schultz GS, Sibbald RG, Falanga V, et al. Wound bed preparation:a systematic approach to wound management. Wound Repair Regen 2003;11:S1-27.
  4. Fletcher J. The benefits of applying wound bed preparation into practice.J Wound Care 2003;12:347-9.
  5. Falanga V. Classification for wound bed preparation and stimulation of chronic wounds. Wound Repair Regen 2000;8:5.
  6. Falanga V, Grinnell F, Gilchrest B, Maddox YT, Moshell A. Workshop on the pathogenesis of chronic wounds.J Invest Dermatol 1994;102:125-7.
  7. National Institute for Clinical Excellence. Guidance for the use of debriding agents and specialist wound care clinics for difficult to heal surgical wounds. NICE: London; 2001.
  8. Thomas S. Assessing the hydro-affinity to hydrogel dressings. J Wound Care 1994;3:89-91.
  9. Thomas S. A comparative study of the properties of twelve hydrocolloid dressings. 1997. Available from URL:?http://www.worldwidewounds.com
  10. Stringfellow S, Russell F. Modern wound management: an update of common products. Nurs Resident Care 2003;7:322-33.
  11. Vowden KR, Vowden P. Wound debridement, part 1: non-sharp techniques. J Wound Care 1999;8:237-40.
  12. O'Brien M. Exploring methods of wound debridement. Br J Community Nurs 2002;Dec:10-8.
  13. Poston J. Sharp debridement of devitalised tissue: the nurses' role.Br J Nurs 1996;5:655-62.
  14. Fairbairn K, Grier J, Hunter C, Preece J. A sharp debridement ­procedure devised by specialist nurses.J Wound Care 2002;11:371-5.
  15. Edwards J. Sharp debridement of wounds. J Commun Nurs 2000;14:1.
  16. Thomas S, Jones M. The use of ­sterile maggots in wound management. Educational Leaflet. London: Wound Care Society; 1999.
  17. Thomas S, Jones M. Maggots can benefit patients with MRSA. Practice Nurse 2000;20:101-4.
  18. Thomas S, et al. The effect of containment on the properties of sterile maggots. Br J Nurs 2002;11(12):21-8.
  19. Collier M. Wound bed preparation. NTplus 2002;98:2.
  20. Landsdown AB, Jensen K, Jensen MQ. Contreet Foam and Contreet Hydrocolloid: an insight into two new silver-containing dressings. J Wound Care 2003;12:6.
  21. Birchall L, Street L, Clift H. Developing a trust-wide centralised approach to the use of TPN.J Wound Care 2002;11:311-4.

Resources
Surgical Materials Testing Laboratory
For information on maggots
W:www.smtl.co.uk
 
Coloplast
For information on products and training
W:www.coloplast.co.uk
 
Smith & Nephew Wound Management  
For information on products and training
W:www.snwmd.co.uk

Smith & Nephew Acticoat
For information on silver
W:www.acticoat.com
 
World Wide Wounds
An online resource for dressing ­materials and practical wound ­management information
W:www.worldwidewounds.com

Evidence Based Nursing Online
W:www.evidencebasednursing.com

National Institute for Clinical Excellence
W:www.nice.org.uk

NHS Direct
W:www.nhsdirect.nhs.uk

Convatec
For information on products and training
W:www.convatec.com
   
KCI Medical
For information on products and training
W:www.kcimedical.co.uk