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Exudate and maceration in wound care

Julie Smith
SRN ONC
Specialist Nurse
General Practice Nursing
Chaddlewood Surgery
Devon

Exudate is a clear, straw-coloured liquid produced by the body in response to tissue damage. If you puncture a blister the fluid that escapes is exudate. If the fluid is discoloured or cloudy, it is a strong ­indication that there is infection in the wound.
The composition and function of wound fluid is generally not well understood.(1) Thomas suggests wound exudate is: "A generic term given to liquid produced from chronic wounds, fistulae or other more acute injuries once haemostasis has been achieved. Exudate is essentially blood from which the majority of red cells and platelets have been filtered out."(1) However, it is important to remember that the components of exudate may vary from patient to patient.(2,3)
 
What does exudate do?
The initial action of exudate is to flush away any foreign material from the site of the injury. It keeps the wound moist and supplies it with nutrients and leucocytes to control bacteria.(4) Exudate acts as the carrier medium to bring fibrin and other repair materials to the site of the injury. Later in the inflammatory response it acts as the carrier for polymorphs and monocytes and supplies them with oxygen and nutrients while they ingest bacteria and debris in the wound. The presence of exudate also enables the movement of these phagocyte cells within the wound. Later in the healing process the new tissue to help in the generation of granulation tissue uses the nutrients in the exudate. Exudate acts as a lubricant, speeding up the migration of epithelial cells across the wound surface to complete initial repair of the wound.
 
The positive and negative effects of exudate
In 1962, it was demonstrated that wounds bathed but not saturated in exudate epithelialised almost twice as quickly as the wounds exposed to air. Despite this work, Thomas states that the ideal moisture content of a wound has still not been established.(1) Further research indicated that exudate from chronic wounds contains higher concentrations of activated enzymes that destroy fibronectin, an adhesion molecule that plays an important part in the healing process.(2) Generally the literature discussing the components of exudate does not differentiate between acute and chronic wounds, and this may be an important omission.
If there is too much exudate in a wound, the surrounding skin becomes macerated and starts to break down under attack from the released enzymes, leaving a worse wound than when you started. If there is too little exudate retained in a wound, the dressings will start to adhere to the wound bed, causing pain and damage to the granulation tissue at dressing changes. In addition, the wound will tend to become sloughy or necrotic, as the irrigating effect of the exudate is lost.
Therefore the ideal wound surface should remain moist, with a thin layer of exudate retained in the wound bed and all the excess removed by the dressing.

Management of exudate
In order to manage exudate effectively, the nurse needs to establish the cause and whether the exudate production can be reduced. An unusually heavy or malodorous exudate may mean there is infection present.(5) However, be cautious, as exudate is often misinterpreted as a sign of infection, which has led to the widespread use of antibiotics for patients with chronic ulcers.(6)
It is important to look for other signs of infection. The traditional criteria to diagnose an infection are the presence of heat, pyrexia, redness, pain, swelling and the presence of pus. Additional signs of infection include:

  • Delayed healing - most produce exudate.
  • Discolouration.
  • Friable granulation tissue that bleeds easily.
  • Abnormal smell.
  • Bridging of epithelium or soft tissue (maceration).
  • Pocketing at the base of the wound.(7)

Exudate results from oedema, which has a variety of causes, including inflammation, immobility, limb dependence, and venous and lymphatic insufficiency.(8) Measures to reduce oedema should therefore result in reduction of exudate. Oedema can be partially resolved by elevating the affected limb or by sustained, graduated external compression where clinically indicated (ie, in venous insufficiency).(1) However, some wounds are so heavily exudating that compression alone is ineffective.(9) Some authors also recommend passive and active exercises to encourage venous return.(8) Diuretics can be used to treat oedema, but must not be used in the long term in simple gravitational oedema. In addition, the elderly are particularly susceptible to the side-effects of diuretics.(10)

Taking swabs
The presence of bacteria in the wound does not constitute an infection itself; the presence of tissue reaction is required for diagnosis of an infected wound. ­
If antibiotics are commenced after confirmation of infection, exudate production should decrease.

Nutrition
There is much research on the role of nutrition in the healing process, but little on how diet specifically affects exudate production. There is high loss of protein in exudate. One study of 50 patients showed that hypoalbuminaemia (low plasma protein) was present in 42% of patients with superficial sores and 77% of those with deep sores.(11)
Other researchers have explored how low plasma protein will cause reduction in the osmotic pressure of the blood, resulting in accumulation of fluid in the tissue spaces (ie, oedema).(12) A high-protein diet will increase the protein present in plasma, although the half-life of albumin is 21 days and it will take some time before levels rise.(11) Encouraging patients to increase their protein intake, either by diet or supplements, will cause fluid to remain within the circulating blood volume and oedema and exudate production to decrease.

Exudate and maceration
If attempts to reduce the exudate have not been successful then it is important to investigate methods of management that will avoid the problems associated with heavily exuding wounds, such as maceration of surrounding skin. Before opting for a dressing to carry out this job it may be useful to revisit the reasons why there is maceration. It could be caused by:

  • Bacteria growth in the wound.
  • Foreign bodies.
  • Rough removal or replacement of dressings.
  • Fingers probing the wound.
  • Swabbing.
  • Chemical application.
  • Malignancy.

Which dressings to choose
There is no correct dressing for the treatment of wound exudate at different stages of healing or to prevent maceration around chronic wounds.(13) Patients have different requirements and expectations from dressings, and these need to be considered.
There are many dressings currently available for moist wound healing, which includes lightly exuding to heavily exuding types. Some even claim to maintain surrounding skin in a healthy state.(14)
One of the major factors influencing wound management is the assessment skill of the nursing staff. One study found that even highly experienced nurses were unable to classify wounds accurately.(1) A survey in one health authority found inappropriate dressings were being used in approximately 85% of cases.(15)

What next?
We should campaign for research that is independent of dressing manufacturers. Results should be made freely available so nurses have informed choice. All dressings should be available on the drug tariff so that nurses are able to provide appropriate individualised care.

References

  1. Thomas S. Assessment and ­management of wound exudate. J Wound Care 1997;6(7):327-30.
  2. Wysocki A. Wound fluids and the pathogenesis of chronic wounds. J Wound Ostomy Continence Nurs 1996;23:283-90.
  3. Krieg T, Eming A. Is exudate a ­clinical problem? A dermatologist's view. From the Proceedings of the European Tissue Repair Society (ETRS) and European Wound Management Association (EWMA) First Combined Meeting: Management of Wound Exudate. Jan 31-Feb 1 1997; Oxford: 13-16.
  4. Quick A. Dressing choices. Nurs Times 1994;90(45):71-2.
  5. Kerstein M. The scientific basis of healing. Adv Wound Care 1997;10:30-6.
  6. Lindholm C. How is exudate currently managed in specific wounds? Community experience. From the Proceedings of the ETRS and EWMA First Combined Meeting: Management of Wound Exudate. Jan 31-Feb 1 1997; Oxford: 29.
  7. Cutting K, Harding K. Criteria for identifying wound infection. J Wound Care 1994;3(4):198-200.
  8. Armstrong S, Ruckley C. Use of a fibrous dressing in exuding leg ulcers. J Wound Care 1997;6(7):322-4.
  9. Hofman D. How is exudate currently managed in specific wounds? Leg ulcers. From the Proceedings of the ETRS and EWMA First Combined Meeting: Management of Wound Exudate. Jan 31-Feb 1 1997; Oxford: 25-6.
  10. British National Formulary 34. London: BMA; 1997.
  11. Lewis B. Protein levels and the ­aetiology of pressure sores. J Wound Care 1996;5(10):479-82.
  12. Hunt P, Sendell B. Nursing the adult with a specific physiological disturbance. London: Macmillan; 1997.
  13. Leaper DJ. Prophylactic and ­therapeutic role of antibiotics in wound care. Am J Surg. 1994;167(1A):15S-20S.
  14. Banks V, et al. Evaluation of a new polyurethane foam dressing. J Wound Care 1997;6(6):266-9.
  15. Miller M. The ideal healing ­environment. Nurs Times 1994;90(45):62-8.

Resources
E-jottings About Tissue Viability
W:www.yeoman.org.uk
European Wound Management Association
W:www.ewma.org