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Foam dressings and excessive wound exudate

The effective management of a patient with a highly exudating wound can be challenging to even the most experienced practitioner
Leanne Atkin MHSc RGN
Lecturer/Practitioner, School of Human and Health Sciences, Centre for Health and Social Care Research, University of Huddersfield, Yorkshire, UK
Karen Ousey RGN PhD
Reader, School of Human and Health Sciences, Centre for Health and Social Care Research, University of Huddersfield, Queensgate, Huddersfield, Yorkshire, UK
Wounds, whether acute or chronic, naturally produce a fluid known as exudate. Injury to the skin triggers an inflammatory response and during the inflammatory process the capillaries dilate becoming more permeable which then allows fluid to leak into the surrounding tissues, when this leaked fluid enters a open wound it is known as exudate.(1) Exudate is often viewed negatively, when in fact wound exudate is known to assist wound healing by preventing the wound from drying out, aiding cell migration, providing nutrients, enabling diffusion of immune and growth factors and assisting in autolysis.(2) However, in wounds that are failing to heal exudate levels can become increased that can have a detrimental effect on wound healing. Excessive exudate can result in delayed wound healing, maceration of the surrounding tissue and subsequent increase in wound size; additionally excessive exudate levels can have a significant impact on a patient’s quality of life. At any one time 200,000 individuals in the UK have a chronic wound; mostly leg ulcers, pressure ulcers and diabetic foot ulcers.(3)
Cost of wound dressings
The cost of wound dressings impact significantly on National Health Service (NHS) budgets; the NHS in England spent £134 million on dressings dispensed in primary care between October 2010 and September 2011. This figure only includes dressings obtained through FP10 prescriptions, so the actual spend on wound dressings is no doubt greater if all routes of procurement are considered including NHS supply chain and direct purchase from the manufacturer. In 2010, foam dressings cost the NHS between £6m to £7m per quarter, which equates to £24 to £28 million per year.(4) When considering the costs of wound care it is vital to consider all aspects of the patient pathway not just the unit cost of the dressings. Posnett and Franks(3) calculated that the total costs to the NHS of caring for patients with wounds was estimated to be between £2.3 and £3.1 billion per year, which represented around 3% of the total 2005–2006 NHS budget. Advanced wound dressings may be more expensive per unit but when consideration is given to less frequent dressing changes resulting in reduced nursing time, advanced products can provide a more cost-effective solution to dressings that require daily changes. 
The successful management of wound exudate needs to begin with assessment including why exudate levels are increased, a number of factors can influence the production of exudate; these include underlying pathophysiology, location of the wound, size of the wound, bacterial burden and the presence of oedema.(5) Each practitioner needs to be able to recognise and understand these systemic and local factors which influence exudate levels and wherever possible address/manage these, therefore aiding the reduction in the volume of exudate. For example, the levels of exudate from a venous leg ulcer will reduce once compression therapy is commenced; levels of exudate from an infected wound will reduce once the bacteria burden is controlled. Choice of appropriate wound product is essential to effectively manage the exudate therefore preventing patient discomfort, promoting wellbeing reducing the the potential for extension of wound size and damage to the peri -wound area through maceration.
The exudate itself, changes of exudate types and level of exudate can hold valuable information for the practitioner as it reflects the underlying condition of the wound and the overall condition of the patient (Table 1). Therefore, accurate assessment of the exudate is required and should include the volume of exudate, viscosity, colour, condition of the surrounding skin and whether there is any evidence of strike-through at dressing renewal. The characteristics of exudate may indicate components, contaminants or underlying causes of increasing exudate levels, for example, green exudate may be indicative of increase bacteria burden, which is likely to be Pseudomonas aeruginosa, or clear, low viscosity (thin and runny) exudate indicates low protein content that could be due to venous/lymphatic insufficiency or malnutrition.(6) Accurate assessment of the underlying pathophysiology in combination with assessment of the wound, including the exudate, is key to aiding reduction in exudate levels. 
Dressing selection
To promote optimal wound healing, an appropriate wound dressing needs to be chosen and applied. For wounds that are highly exuding, the dressing needs to maintain a moist and humid wound bed while rapidly removing and holding excessive exudate away from the wound within the dressings, thereby preventing maceration to the surrounding skin.  Maceration can easily occur if exudate is not effectively managed; maceration is where the edges of the wound become white due to the direct contact of the wound fluid (Figure 1). If exudate is not managed correctly, the surrounding skin can start to break down over a period of time, resulting in extension of the wound size and increased levels of discomfort for the patient.(7)
There are a variety of general wound products designed to assist in the management of exudate management. These include: wound pads (for example, Surgipad from Systagenix), foam dressings (for example, Allevyn from Smith and Nephew), hydrofibre dressings (for example, Aquacel from Convatec) and super-absorbent dressings (for example, KerraMax from Ark Therapeutics). Foam dressings possess characterises of an ideal wound dressing as they provide a moist wound environment, are thermally insulating, mechanically protect the wound, allow atraumatic dressing removal, permeable to gases including oxygen and water vapour while providing a physical barrier.(8) Foam dressings may possess all the attributes of a ideal wound dressings however the decision of which dressing to be used is based on a variety additional factors including the ability to manage the current volume of exudate, the condition of the surrounding skin, the unit cost of the dressings, the frequency of the dressing change, patient comfort and nursing time. More advanced products, such as the super absorbent, might be more expensive in terms of unit costs but the expense of the dressings can often be offset by fewer dressing changes,(9) as the most costly element of wound management is often health professional time, not the cost of the dressings.
Foam dressings
The most common wound product used to manage exudate are foam dressings; there is currently an extensive range of foam dressings available, they can be used as primary or secondary dressings and come in non adhesive or adhesive versions. Foam dressings first became widely available in the mid-1970s and were one of the first ‘modern’ wound dressings. They are common place on local wound care formularies. There are many dressings that fall under this classification but the chemical composition of each dressing can vary greatly. They are generally classed as either true foams or pseudo-foams. True foams are commonly composed of polyurethane or silicone, the foam dressing draws fluid into air spaces via capillary action; they have a hydrophilic contact layer that encourages the fluid to pass through the dressing away from the wound bed. The fluid is then held within the foam structure and the backing of the dressings is designed to allow evaporation of small amounts of fluid therefore enhancing the dressing total fluid capacity handling. Pseudo-foams are hydroactive dressings that draw the fluid into the dressing, as the fluid is absorbed the dressing physically expands. They contain absorbent polymers which have the ability to swell to 20–30-times their original size and trap the fluid within their structure therefore have the ability to absorb high volumes of fluid.(10)
Management of wounds with high exudate levels
The choice of which dressing to use is based on a number of factors these include: condition of wound bed and surrounding skin, level of exudate, location and aetiology of wound, wear time, comfort and conformability, patient’s choice and ease of use. The advantages of choosing foam dressings for medium to heavily exudating wounds is that they will not shed fibres unlike gauze- or wadding-based products, the ability to manage the exudate levels will prevent surrounding ulcer maceration and dressings strike through, strike through is when the absorbed fluid reaches the outer surface or edge of the dressings, this occurs when the dressings become saturated. Foam dressings additionally have a non-adherent wound layer ensuring pain-free dressing removal; they have the ability to be left in place for up to seven days and they can safely be used in a variety of scenarios including under compression bandages, on difficult to treat wound such as diabetic foot ulceration and on infected wounds.  Clinicians believe there are many advantages in using foam dressings in medium to high exudating wounds, but presently there is little evidence to support their use. O’Meara and James(11) reviewed the evidence relating to whether foam dressings applied beneath compression bandaging healed venous leg ulcers more quickly than other wound contact layers. 
They concluded that foam dressings were no better or worse than any other primary wound contact layer, but did state there was a general lack of good quality evidence as such they were not able to draw definitive conclusions regarding the efficacy of foam dressings.  A further review performed by Dumville et al(12) investigated whether foam dressings increased healing rates of diabetic foot ulcers and performed a comprehensive review of the current evidence. They found that foam dressings do not increase healing rates of diabetic foot ulcers compared with alternative dressings. It is important to note that both of these reviews did not distinguish between wounds with low or minimal levels of exudate and wounds with medium to high volumes of exudate, potentially by including low exudating wounds (which wound not require foam dressings) could have affected the overall results. Dumville et al(13) did conclude their review by stating that there was a general lack of good quality evidence therefore practitioners may elect to consider other characteristics such as costs and symptom management properties when choosing between different wound dressings. 
The effective management of a patient with a highly exudating wound can be challenging to even the most experienced practitioner. For successful outcomes, wounds need to be assessed in combination with the overall patient condition and never in isolation, to ensure full understanding the underlying systemic and local conditions which are influencing wound exudate production. Accurate assessment and the treatment of underlying conditions in combination with appropriate dressing selection is key to promoting successful wound healing and to ensuring that the patient’s quality of life is not negatively affected. Foam dressings continue to be a common and anecdotally successful option for the management of moderate-to-highly exudating wounds despite the lack of clear research evidence supporting their use.
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