Julie Vuolo, BA (Health Care Studies), RN, DipHE (Tissue Viability).
Lecturer, University of Hertfordshire
Exudate is a fluid produced as part of the normal wound-healing process, and is essentially blood from which the platelets and red cells have been filtered out (Thomas, 1997a).
It leaks from capillaries in the tissues surrounding a wound as a consequence of increased capillary permeability.
Increased capillary permeability occurs either as part of the early inflammatory response that follows any tissue injury or as part of the host response to large numbers of bacteria in the wound bed (White, 2000). As the single-cell (endothelial) capillary walls are stretched widely spaces appear between the cells and fluid leaks into the interstitial spaces and ultimately into the open wound bed. The fluid varies widely in appearance, consistency and quantity. This variation in the type of exudate and the nature of the associated wound causes many of the problems health professionals face in providing the optimum wound care for patients with highly exudous wounds.
Although this paper focuses on the management of excess exudate, other causes of fluid leakage through the skin pose similar problems. For example, transudate is excess fluid forced out as a result of raised capillary pressure in the lower limb, while lymphorrhoea is fluid leakage as a result of failure in the lymphatic system. Both can result in excess fluid loss and associated skin damage. In addition, oedema, such as that resulting from low blood-protein levels or intravenous fluid overload, can result in loss of fluid through the skin and, although fluid losses may not be high, persistent low-level loss can still have a considerable impact on skin and wound health.
The importance of managing exudate
High levels of wound exudate can mean patients have to wear soiled, wet, heavy dressings that regularly leak and often smell. Healing can be delayed and surrounding skin can be badly damaged due to maceration and excoriation. In practical and economic terms frequent laundering of clothing, linen and furnishings can be a problem (Anderson, 2002), as can the effect on work and social interactions. In psychological terms the reality of coping day to day with such an intrusive problem should not be underestimated, nor should the strain it can put on carers and the carer/patient relationship. If the problem persists it can result in social isolation and even the onset of clinical depression.
For the health service, the management of excess exudate can mean considerable costs in terms of health professionals’ time spent on frequent visits to change dressings and in money spent on dressings and associated items such as skin protection and analgesia (Robinson, 1997). It can also be frustrating for health professionals if they have limited knowledge of good management strategies or a lack of resources with which to implement them.
The role of exudate
Following Winter’s original research in 1962, it is now widely accepted that a certain amount of moisture in the wound bed is necessary for optimal healing. The difficulty is in determining what that ‘certain’ amount is. Part of the problem is that the constituents of exudate vary from wound to wound (Baker and Leaper, 2000; Wysocki et al, 1993; Wysocki, 1996). In acute wounds it plays a crucial role in delivering a variety of substances essential to healing, such as growth factors, nutrients and leucocytes (Fletcher, 2003; Thomas, 1997a). In persistent or chronic wounds, however, its constituents differ. In particular, the high levels of proteinases (naturally occurring enzymes which actively destroy proteins) found in chronic wound exudate cause considerable problems (Baker and Leaper, 2000). When allowed to proliferate these proteinases can destroy healthy tissue and consequently complicate the progress toward healing. Possible indicators of proteinase damage are:
- Discoloration of the wound bed
- Excoriation at the wound margins and in the surrounding skin
- Pain in and around the wound
- A delay in the overall pace of healing.
It is not only the constituency of exudate that is important in determining its effect on healing, but also the quantity. High levels of fluid, when left in contact with the skin, can cause maceration even when the fluid constituents are relatively benign. Macerated skin, recognised by its whitish, plump, soggy appearance, will break down easily and can result in an increase in the overall size of the wound (Nelson, 1997). It is therefore important not to confuse macerated skin with new epithelial tissue, which is soft and pale pinkish/white in colour, because measures instigated to resolve maceration can retard or damage fragile new growth (Bolton et al, 2000).
Assessment is the crucial first step in the management of highly exudous wounds. The assessment process should include a description of the nature and amount of the exudate, as well as identification of the cause. This information can then be used to develop an effective treatment plan.
Describing exudate nature and amount
A description of the exudate can be a useful indicator of a wound’s progress or otherwise. The presence of blood in exudate may indicate wound infection, an underlying bleeding disorder, malignancy or trauma to the wound bed, while the presence of a purulent discharge may indicate infection or heavy colonisation of a wound. Mulder (1994) suggested standardising the terms used to describe exudate, and proposed four descriptors:
- Serous (thin, watery, like serum)
- Sanguinous (containing red blood cells)
- Serosanguinous (containing blood and serous fluid)
- Purulent (containing pus).
Using these or similarly standardised terms in the assessment process can improve the quality and consistency of the information gathered, provided that all users understand and agree the meaning of the terms employed.
Measuring exudate loss
Measuring or quantifying fluid loss is perhaps more difficult than describing it. While exudate loss can be measured by weighing dressings or by measuring the contents of wound drainage bags or canisters, this is often impractical. Issues such as how dressings should be transported to the weighing area, what weighing machinery is used, how it is cleaned and the amount of time involved all make routine weighing of dressings impractical both in clinical areas and in patients’ own homes. While wound-drainage bags may make weighing the exudate easier, they are unsuitable for many wound types, as are therapies such as vacuum-assisted closure (VAC), although they incorporate a fluid collection canister with an integral measuring scale.
In many cases, the observation of exudate loss is made on the basis of the saturation or otherwise of the wound dressing at specified intervals, such as every 24 or 48 hours. This method relies on the observer’s interpretation of what they see and the fluid-handling capability of the dressing used. However, if the dressing type is stated clearly and the times at which strike-through occur is documented (Figure 1) this approach will provide a useful record of how the dressing is managing the exudate. It is also accessible to all practitioners and more accurate than using non-specific descriptive terms such as low, moderate and large or even +, ++ and +++, which can be interpreted in a variety of ways and can be particularly misleading if used in isolation from other wound- assessment descriptors.
In fact, measuring exact quantities of fluid loss may be of little importance. What is important is the impact of exudate loss on the patient and wound. If the dressing is handling the fluid loss effectively so that the wound bed condition is satisfactory and the surrounding skin is undamaged, then the exudate loss is being successfully managed. If the wound bed is failing to progress as expected, the surrounding skin is excoriated and dressings are being changed several times as day, it is not being managed successfully and is therefore presenting a clinical problem that must be addressed swiftly.
Identifying the cause(s)
A number of factors have been identified as contributing to high exudate production (Box 1); below some of the more easily recognised ones are discussed.
A chronic inflammatory response can result in a highly exudative wound (Hart, 2002). Inflammatory ulcers such as those seen in association with rheumatoid arthritis or vasculitis may require systemic steroid treatment to slow or stop the response and thereby reduce the high levels of exudate production. Patients may require specialist assessment by a rheumatologist or dermatologist and biopsy to confirm diagnosis before treatment is commenced.
Local irritation, such as that caused by an uncomfortable dressing, a foreign body or a skin condition such as pruritus or eczema, can also contribute to high exudate levels - particularly if scratching is involved. If an allergic response is suspected the patient should be referred to a dermatology unit for patch testing to identify the allergen(s). Removal of the irritant and the use of bland emollients such as 50/50 white soft and liquid paraffin may break the itch/scratch cycle.
As stated previously, a high bacterial burden within the wound can lead to excess exudate production as a result of increased capillary permeability. Infection can be difficult to identify but observation of key clinical signs such as increased pain, the presence of pus and malodour (Cutting and Harding, 1994; Gilchrist, 1999) and judicious use of wound swabs, exudate culture and tissue biopsy, will assist the practitioner. High exudate production may also be seen in cellulitis and erysipelas. Differential diagnosis is important, but both conditions have the potential to blister and fluid loss from damaged blisters and/or associated ulcers can be significant. Clinically infected wounds may benefit from the use of topical antibacterial agents such as silver- or iodine-based products when systemic antibiotics alone are insufficient, for example due to poor vascular supply (White et al, 2001) and/or oedema.
Venous hypertension is possibly the most common cause of high levels of exudate in the lower leg. Diagnosis should be made on the basis of clinical signs and symptoms and the use of Doppler ultrasound to calculate the ankle-brachial pressure index (RCN Institute et al, 1998). Fluid loss associated with venous hypertension alone can usually be brought under control by the correct application of compression bandaging (RCN Institute et al, 1998).
It is also important to remember that some wound treatments may increase (or apparently increase) wound fluid loss. Hydrogels (water-based desloughing agents) add fluid to the wound bed, while VAC actively draws fluid out from the wound and surrounding tissues (Morykwas et al, 1997). Larval therapy also results in an increase in exudate production during the first few days after treatment begins.
Whatever the underlying cause - and there may be more than one - accurate assessment and diagnosis are essential. Appropriate clinical investigation and specialist referral should also be made where necessary.
Options for care
A number of factors can influence the choices of care made. The main ones are discussed below.
Type of wound and status of wound bed
Different types of wounds require different treatment approaches according to their aetiology and the status of the wound bed at the time of assessment. For example, graduated high compression is ideal for heavily exuding venous ulcers but is contraindicated for malignant wounds, however exudous. Similarly, hydrogels are suitable for desloughing in dry to moderately wet wounds but become ineffective in very wet wounds. If there is slough or necrosis in the wound bed it is preferable to either sharp debride it (according to local policy) or to allow it to loosen through the natural process of autolysis in conjunction with a suitable dressing.
Malodour, which can be a cause of great distress to the patient, may improve with the use of dressings incorporating carbon/charcoal or a topical preparation containing an antibacterial agent such as metronidazole (Dealey, 2000).
Wound position, size and shape
A wound over a joint will require a flexible dressing to retain joint motility, while one near the anus may require specific skin protection against faecal contamination. It is also important to drain excess exudate away from the wound bed, which can be particularly difficult to do if the patient is immobile. In such situations VAC can be useful as it draws fluid away from the wound bed and the surrounding skin.
Shallow wounds can be covered by flat dressings, taking care to ensure the dressing comes into contact with the wound surface to permit effective fluid absorption. Dressings designed for filling deep wounds should be used in cavities to encourage granulation growth from the base of the wound, although care should be taken not to pack tightly as this can result in localised ischaemia and tissue death (Flanagan, 1997). Foam stents can also be made to closely fit the wound bed contours. Any sinuses or fistulae should be able to drain fairly freely, with enough dressing to absorb excess fluid and prevent premature closure of the wound but not so much as to cause tissue damage.
In recent years the availability of different dressing sizes and shapes has improved considerably and many companies offer ready-made shapes to suit ‘awkward-to-dress’ areas. Local sterile supplies units can also sometimes help by producing made-to-measure pieces of sterile secondary dressings for very large wounds.
Knowing what, if any, conditions or diseases from which the patient suffers (especially those that affect wound healing) is also a crucial factor in devising an appropriate plan of care. Patients who have malignant disease may not be suitable candidates for compression therapy, VAC, enzyme or larval debridement. Those with diabetes are more prone to the rapid development of wound complications (Foster, 1999) therefore dressings for diabetic ulcers are often chosen because they can be easily removed to allow for regular wound inspection.
Any plan of care must be made with the patient’s knowledge and approval, particularly if their co-operation is an integral part of the plan. For example, many elderly patients find leg elevation extremely difficult but are more likely to try it if they understand that gravity will aid the return of fluid to the circulatory system and, as a consequence, reduce exudate loss. The patient may also have other medical, psychological and social needs, any of which might conflict with the proposed management of the wound. All members of the multiprofessional team must therefore work together so that the overall plan of care reflects all the patient’s needs. This kind of holistic approach to wound management is far more likely to yield patient concordance.
A number of dressing types are suitable for exudate management. These various products handle fluid in different ways; some simply absorb the fluid at the point of contact with the wound, while others spread it laterally (wicking), making full use of the dressing’s total size.
The main categories of dressing to choose from for exudate management are alginates, hydrofibres and foams. Alginates work by absorbing wound fluid into the dressing matrix, while hydrofibres absorb it into the actual dressing fibres. Both are available in flat and ‘rope’ presentations which can be used on flat/shallow wounds and in cavities respectively. They each turn gel-like on contact with exudate and therefore provide a moist interface with the wound, which in turn promotes autolysis and granulation. Both require a secondary dressing to hold them in place. Although they appear similar hydrofibres are capable of absorbing more than alginates because of their mode of action; for this reason they should be first choice for use on a heavily exuding wound.
Foam and hydropolymer dressings are both manufactured from polyurethane but vary considerably in their design and fluid-handling ability. They are capable of absorbing moderate to large amounts of exudate and can be obtained as both flat and cavity presentations.
In addition, hydrocolloids and semi-permeable films may be useful as secondary dressings. Hydrocolloids are not designed to absorb large amounts but can be used for dressing retention in combination with a more absorbent dressing such as a hydrofibre, or for skin protection. Semi-permeable films can also be used for dressing retention but with caution. Poor application and removal technique can cause skin stripping, and covering with an impermeable padding or tape can result in fluid being trapped against the skin with the development of maceration or excoriation as a consequence.
Achterberg and Meyer-Ingold (1996) describe dressings which selectively absorb exudate, soaking up the fluid component while leaving behind the ‘beneficial’ wound proteins on the wound surface. However, Fletcher (2003) advocates careful consideration of this option in light of emerging knowledge of the potentially damaging effect of proteins in chronic wound exudate (Trengove et al, 1999; Yager and Nwomeh, 1999).
Whichever dressing is selected it remains important to remember the manufacturer’s claims of fluid-handling ability are for guidance only and depend very much on the nature of the individual wound and on the length of time the dressing is worn (wear time). It is important to give dressings a realistic chance of working by trying different wear times before deciding that the dressing is not working.
Dressing retention and skin protection
Dressings for exudate management can be bulky even before they come into contact with exudate, at which point they can also become very heavy. This can cause considerable discomfort to the patient and can also damage the skin by ‘dragging’. Attention should therefore be paid to selecting a suitable method of dressing retention that minimises skin trauma. The use of adhesive dressings reduces the need for secondary dressings and tapes or bandages to secure them. They tend to be more secure for longer than non-adhesive dressings, but cannot be used where the peri-wound skin is either damaged or vulnerable to damage, or where repeated dressing removal is necessary. Alternatively, ordinary or tubular bandages can be used to secure non-adhesive dressings, thereby preserving skin condition. They can also be removed easily for wound inspection or dressing replacement.
Skin protection is of paramount importance. While barrier creams and ointments can be useful in skin protection they can also affect the dressing’s mode of action by blocking the passage of exudate into the dressing itself (Anderson, 2002). Alternatively, skin-care products such as Cavilon No Sting Barrier Film (3M) have proved effective in preventing and managing erythematous skin damage resulting from contact with wound exudate (Neander and Hesse, 2003). They may also reduce skin stripping by providing a contact layer which interfaces between the dressing and the actual skin surface. Thin hydrocolloid wafers can be used for the same purpose, to protect vulnerable or damaged skin and as anchor dressings onto which further adhesive dressings or tapes can be secured.
Vacuum-assisted closure and wound drainage bags
Aside from absorbent dressings, VAC and wound- drainage bags can both be used to collect large volumes of exudate. Vacuum-assisted closure creates a vacuum in the wound bed and then mechanically sucks the fluid from the wound and surrounding oedematous tissues. As a sealed unit VAC is also useful in minimising the risks of cross-infection to other patients and possibly even in reducing the bacterial counts in colonised wounds (Morykwas et al, 1997). Wound-drainage bags can also be used on some wounds, and some patients may be able to learn to use bags for themselves. However, both VAC and drainage bags require particular care with fitting and skin protection to ensure exudate does not come into contact with the surrounding skin. Anderson (2002) also cautions against allowing drainage bags to overfill as this can lead to skin trauma from pulling as well as the risk of leakage onto the surrounding skin and clothing.
The management of excess exudate relies on skilled assessment and a thorough knowledge of the available options for care. It is particularly important to establish why excess exudate is being produced so that appropriate measures such as leg elevation and systemic antibiotics can be used in addition to absorbent wound dressings. Good skin care and protection is also paramount given the damaging effects of exudate. When decisions for care have been made it is important to ensure that the manufacturer’s instructions for use are followed and that wear times are adjusted according to the individual’s needs. Above all, it is crucial to ensure that the needs and wishes of the patient remain central to the choices made.
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