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Leaking wounds: how to manage exudate

Una Adderley
DN RGN BA BSc
Community Tissue Viability Nurse
Scarborough, Whitby and Ryedale PCT

Exudate is the fluid that is produced by an open wound. If the wound is open and healing by secondary intention then exudate will leak from the surface of the wound. A small amount of exudate may also be leakage from wounds that are healing by primary intention, when the edges of the wound have been brought together with sutures or other materials, but where there is incomplete closure.

The role of exudate
The production of exudate is part of the normal healing process during the initial inflammatory phase (before the proliferative and maturation phases). During normal healing, the fluid, which is usually found in the extracellular space, combines with additional fluid that has left the blood supply as part of the inflammatory response to wounding. Exudate contains six times as many white blood cells as blood.  
Healthy exudate is usually a clear, straw-coloured liquid, although there may be some variation both between individuals and as a result of external factors, such as temperature. Acute wound exudate contains high levels of growth factors and plays an essential role in the healing process by providing the necessary nutrients and oxygen to the tissue before draining back into the lymphatic system.(1) In the normal healing process of an acute wound, the volume of exudate will decrease as healing progresses. However, high levels of exudate may hinder healing if the capillaries are unable to cope with the increased volume of fluid.
Chronic wound exudate differs in that it is rich in growth factor nutrients and leucocytes. Although these support healing through the stimulation of fibroblast and epithelial cell production,(2) chronic wound exudate also contains high levels of proteases that are thought to have an adverse effect on healing. Chronic wound exudate is also thought to be more corrosive than acute wound exudate and is known to contribute to peri-wound skin irritation or allergic contact dermatitis.(3)

Assessing exudate
Exudate may vary in colour and consistency between individuals and in different circumstances. However, significant variations in exudate colour, consistency and quantity can be useful clues with regard to monitoring wound progress and diagnosing challenges to healing, such as infection. Wounds that are deteriorating are likely to have exudate that increases in quantity and becomes malodorous.(4)
Accurate assessment of wound exudate can be difficult as assessment is often subjective, as there is currently a lack of standardised terminology and objective outcome measures.(5)
Wound exudate should be assessed using three main categories - volume, colour and odour.(2) Volume of exudate is often assessed using the terms light, moderate and heavy or by using the symbols +, ++ and +++. However, this approach is very subjective and unreliable. A more reliable approach might be to weigh a dressing after removing it, but this is usually clinically impractical. It may also be unreliable if the dressing is designed to have a high moisture vapour transmission rate, when a significant proportion of exudate may evaporate and be lost to the record. Another approach might be to note the frequency of dressing changes. In normal healing, the volume of exudate should steadily decrease, and thus the time between dressing changes should extend.
Healthy wound exudate is usually pale amber or straw. The colour of wound exudate can change in the presence of heavy microbial colonisation or infection. For example, Pseudomonas aeruginosa may cause a distinctive yellow/green staining on the dressing, although clear, watery, serous exudates may also contain bacteria such as Staphylococcus aureus. Heavy levels of microbial colonisation may lead to friable granulation tissue that bleeds easily, thus turning exudate bloody.  
Odour may also be a useful indicator. Again, the presence of colonising P aeruginosa may lead to its own distinctive malodour recognisable to most wound care clinicians. Haemopurulent exudate that is yellow/brown may be indicative of more serious bacterial colonisation that has led to abscess formation or systemic infection. Faecal malodour may be due to the presence of a fistula originating in the bowel.
Uncontrolled exudate can make patients' lives miserable. Soiling of clothing and bedding due to uncontrolled exudate is likely to be embarrassing as well as inconvenient. The loss of large amounts of exudate may also lead to nutritional challenges, as exudate is rich in protein. It has been estimated that a grade 4 pressure ulcer may result in the loss of between 90g and 100g protein per day due to exudate loss.(6)

Managing exudate
Wound infection should be diagnosed by the clinical identification of the classic signs of infection: pain, wound breakdown, purulence, erythema, oedema and heat. Several of these symptoms will be present if a wound is clinically infected. A wound that is clinically infected should be treated with appropriate systemic antibiotics, which may be identified from the results of a wound swab. A wound that is critically colonised will have symptoms that include malodour, slough and indolence (lack of improvement). Wounds that are critically colonised may benefit from treatment with a topical antimicrobial, but, at present, there is insufficient research evidence to indicate which antimicrobial dressings are the most clinically effective. Prophylactic antibiotic treatment should generally be avoided unless the patient is particularly susceptible to infection (eg, patients with diabetes).
The effective management of exudate can be challenging. The first principle is to address the underlying aetiology, where possible. For example, a venous leg ulcer will leak copious amount of exudate unless the venous hypertension is reversed through the application of graduated multilayer compression bandaging. Similarly, a patient in chronic heart failure may leak large quantities of exudate from their legs unless their heart failure is treated with effective diuretic therapy. If a wound is infected then exudate levels are likely to increase until the appropriate antimicrobial therapy reduces the microbial levels, thus allowing healing to recommence.
However, until these therapies take effect and for situations where either the therapy fails or there is no effective therapy, the clinician is left with the situation where exudate needs to be managed effectively.

Dressing selection
The conventional approach has been through the selection of an appropriate dressing. The ideal wound dressing should be able to maintain high humidity at the wound site while removing excess exudate.(7) If exudate levels are very high then the dressing will also need to prevent maceration of the surrounding skin by absorbing exudate rapidly and holding that exudate within the dressing without letting it leak back onto the surrounding skin.
Several categories of dressings are recognised as being particularly suitable for managing exudate. Foam dressings will absorb exudate, but some foams are also designed to transmit moisture vapour away from the wound through evaporation through the back of the dressing. Foam dressings come in a wide variety of shapes, including flat sheets, anatomically shaped dressings specifically for heels and the sacrum, and fillers that can be shaped to the exact size of a cavity wound.  
Alginate dressings absorb exudate to form a gel. Again, they come in a variety of shapes, including flat sheets and ribbon, which can be used to fill a cavity wound. Although many nurses were trained to "pack" a wound to prevent a wound epithelialising at surface level before the cavity has filled with granulation tissue, there is no evidence to support this practice in terms of promoting faster healing. However, it might be argued that placing a filler loosely within a wound cavity as well as using an absorbent dressing over the surface of a wound increases the absorbency capability of a dressing regimen and thus decreases the risk of maceration due to excess exudate. Hydrofibre dressings share similar properties to alginate dressings in terms of exudate management and are thus also useful for managing exudate.

Alternative approaches
There are alternative approaches to dressings for managing exudate. Woundcare bag systems, which resemble stoma bags, may be applied over the wound and used to collect exudate. Woundcare bag systems are available on prescription.
Vacuum-assisted closure (VAC) or negative pressure therapy is another approach to managing copious exudate. VAC has been used in the acute setting for some years but is a relatively recent innovation within community care. A foam dressing is cut to the size and shape of the wound, and a catheter is placed within this dressing. This is then covered by an adhesive drape, such as a film dressing, which provides a continuous airtight seal around the dressing. The catheter is then attached to a vacuum pump unit. This evacuates the air from the foam dressing so that the dressing is in contact with the total surface of the wound. Excess exudate is gently sucked away from the wound surface into a collection canister, thus reducing oedema and improving blood flow. It is believed that this process leads to improved oxygenation and tissue nutrition, thus accelerating healing.(8)
At present, there is little robust research evidence to prove that VAC therapy results in quicker healing. However, VAC therapy is often a very effective way of managing uncontrollable exudate, which is likely to lead to an improved quality of life for the patient. In addition, it is possible that there may be significant cost savings in terms of nursing time, particularly in the community setting. Patients who previously may have required daily or twice-daily dressing changes from the district nurse may only require twice-weekly visits with VAC therapy.

Skin protectants
With all measures for absorbing or removing exudate, protection of the surrounding skin remains an important factor in care. Good hygiene of the surrounding skin will reduce trauma from maceration and excoriation, but barrier products, such as creams and lotions, can play an important role in minimising the damage from excess exudate.

Conclusion
The effective management of exudate plays a major contributing role in wound healing, particularly wound healing by secondary intention. Although there is a lack of robust evidence to support decision-making in this field, decisions that address the underlying aetiology, select the appropriate wound care product and provide dressing changes at intervals that minimise maceration and excoriation should result in effective clinical care.

Practice pointers

  • Ensure that the underlying aetiology is adequately addressed
  • Exudate can provide important clues as to the progress and aetiology of a wound
  • Remember to consider a patient's quality of life and nursing time when assessing the cost effectiveness of a regimen for managing exudate

References

  1. Chen J. Aquacel hydrofibre dressing: the next step in wound dressing technology. London: Convatec; 1998.
  2. Young T. Managing exudate:essential wound healing. Commun Nurs 2000;Suppl (Pt 6).
  3. Cameron J, Powell S. How is exudate currently managed in specific wounds: leg ulcers? In: Cherry G, Harding KG, editors. Management of wound exudate. Oxford: SOFOS; 1997.
  4. Gardner SE, Frantz RA, Troia C, et al. A tool to assess clinical signs and symptoms of localised infection in chronic wounds; development and reliability. Ostomy Wound Manage 2001;47(1):40-7.
  5. Nelson EA. Is exudate a clinical problem? A nurse's perspective. In: Cherry G, Harding KG, editors. Management of wound exudate. Oxford: SOFOS; 1997.
  6. Breslow R. Nutrition status and dietary intake of patients with pressure ulcers: review of research literature 1943-1989. Decubitus 1991;4(1):16-21.
  7. Morison M, Moffatt C, Bridel-Nixon J, Bale S.  A colour guide to the nursing management of chronic wounds. 2nd ed. London: Mosby; 1997.
  8. Benbow M. An update on VACtherapy. J Commun Nurs2006;20(4):28-32.

Resources
World Wide Wounds
Electronic wound management
journal dedicated to promoting good practice and better communication in the specialty of wound care
W:www.worldwidewounds.com
UK supplier of VAC therapy
W:www.kci-medical.com/kci/unitedkingdom