Diabetes mellitus is one of the most common endocrine diseases. It is predicted to affect 239 million people worldwide by 2010, presenting a major challenge to healthcare systems and economies (Mandrup-Poulson, 1998).
Amputation is 15 times more common in diabetic patients than in the non-diabetic population (Williams, 1994). Foot ulcers are the most common reason for hospitalisation in patients with diabetes (Elkeles and Wolfe, 1991), accounting for 20% of admissions in this patient group. Among the 750,000 individuals with diabetes in the UK, 4% will have had an amputation and 6% will have an active foot ulcer at any one time.
Foot ulceration
Foot ulceration can occur in individuals with type 1 or type 2 diabetes. The data suggest that 50% of older patients with type 2 diabetes have risk factors for ulceration (Boulton, 1996).
Ulceration does not occur spontaneously but is commonly the result of either trauma or pressure, which often goes undetected because of the underlying peripheral neuropathic or vascular problems associated with the disease process. The majority of ulcers (90%) are neuropathic (Figure 1) or neuro-ischaemic, with the remainder being purely ischaemic (Figure 2) (Boulton et al, 1994).
Infection is not a primary cause of ulceration, but usually secondary, and is the most serious complication of a diabetic foot lesion (Edmonds, 1984; Boulton, 1996; Sign, 1997). Once infection is established in the diabetic patient, it can be very aggressive and develop rapidly (Baker, 1997). Because of the reduction and alteration in blood flow, defective immunity, and often a lack of patient awareness, systemic infection may quickly ensue, and become life-threatening if left unchecked. Wound care is aimed at eliminating infection if present, or eliminating the factors that precipitate bacterial invasion. Therefore, once ulceration has occurred, it is imperative that the practitioner assesses the degree of damage in order to identify a strategy for preventing infection and to ensure appropriate management.
In many cases the choice of dressing may be less critical than thorough observation and assessment of the wound status. Other treatment modalities may have a greater impact on the management of ulceration: examples include removal and/or redistribution of pressure and friction, and debridement to remove necrotic and/or sloughy tissue or callus, or to drain pus. This not only promotes healing and removes pressure, but also permits examination of the ulcer bed (Knowles and Jackson, 1997).
Wound assessment
Assessment of the ulcer is a prerequisite to any form of treatment. The information gained from the assessment will vary according to the complexity of the assessment tool used. Basic assessment of wound size, shape, type of tissue and surrounding skin will provide the practitioner with limited information on which to base dressing choice. When caring for diabetic patients, a more in-depth assessment that takes account of the vascular and neurological status is required.
A suitable format, suggested by Harding (1992), is the wound healing matrix (Table 1). This general but comprehensive assessment can be adapted to meet the needs of individuals in any healthcare setting. A thorough assessment will ensure that correct management, which includes the selection of an appropriate dressing, is provided.
Dressing choice
Since the work of Winter (1962) and Hinman and Maibach (1963) it has been recognised that a moist wound environment is optimal for wound healing. Most modern wound management products meet some of the requirements of an ‘ideal’ dressing, although these requirements will vary according to the wound type. The properties of an ideal dressing have been described as follows:
- Creates a moist environment at the wound–dressing interface
- Provides thermal insulation
- Impermeable to microorganisms
- Free from particulate contaminants
- Allows removal without trauma
- Acceptable to the patient
- Capable of absorbing excess exudate
- Cost-effective
- Allows monitoring of the wound
- Allows gaseous exchange
- Provides mechanical protection
- Conformable
- Available in hospital and the community
- Requires infrequent changing.
Consideration should be given to the fact that these properties may be altered when the dressing is used on feet (Morgan, 1997), as dressings are not designed to take the high and repetitive forces exerted on the sole of the foot (Baker, 1997).
Dressing choice for the diabetic foot lesion should be based on careful assessment of the neuropathic and/or vascular status of the foot (Knowles and Jackson, 1997).
It is important for practitioners to be able to identify the different characteristics of each ulcer type in relation to complex aetiology, e.g. neuro-ischaemic ulcers do not usually produce a high level of exudate, so that a highly absorbent dressing would be inappropriate (McInnes, 1997). In the presence of infection (Figure 3), however, where exudate levels are likely to be high, the wrong choice of dressing can cause maceration and major deterioration of the wound, with potentially serious consequences.
Dressings should not be too bulky as this will affect the fit of the shoe (Knowles and Jackson, 1997). Foster et al (1994) have simplified the properties of a dressing that meets the needs of the patient with a diabetic foot ulcer as follows:
- Does not take up too much space in the shoe
- Does not increase the risk of infection
- Absorbs exudate
- Can be changed frequently.
However simplified these properties may be, the wide variety of dressing materials currently available may leave practitioners confused. Although many trials have been conducted with dressing materials, the findings do not always provide overwhelming evidence in favour of one dressing over another. If choice of dressing is not based on a systematic framework, dressing materials may be used inappropriately, leading to delay in wound healing and increasing the cost of care.
This type of approach to dressing choice was demonstrated by Fisken and Digby (1996) in a questionnaire survey of diabetes specialist nurses and state-registered chiropodists. They reported that between five and eight different dressings could be chosen for the same type of ulcer. It was not clear from the study whether the inability of respondents to make informed choices was due to lack of information or to a belief that it did not matter which type of dressing was used. The most popular dressings were low/non-adherent, hydrocolloids, hydrogels and alginates.
Dressing types
Traditional dressings such as gauze and absorbent cellulose dressings adhere to the wound bed and cause bleeding on removal (Wijekunge, 1994). They also provide little protection against bacterial contamination, especially if ‘strike-through’ (leakage of exudate) is allowed to occur (Lawrence, 1994).
In contrast, many modern products are designed to be left in place for a number of days. This reduces the risk of contamination, leaves the delicate wound tissue intact and reduces cost (Jones and Harding, 1995). However, this has become an area of contention between specialists, as frequent dressing change is advocated, particularly for infected, diabetic foot ulcers to allow daily wound inspection (Foster et al, 1997; Vowden, 1997).
Although clean, non-necrotic ulcers can withstand dressing changes two or three times a week without ill-effect (Apelqvist et al, 1994), infected foot lesions require at least daily changes (Boulton et al, 1997).
Using an appropriate rationale based on individual patient characteristics determined from the wound assessment, the practitioner can select a dressing according to the criteria shown in Table 2.
Conclusion
Selection of an appropriate dressing is an important factor in the successful management of diabetic foot ulcers. It is important for practitioners to understand the general and specific properties of modern dressing materials in order to make a rational, research-based choice.
This overview of dressing selection for diabetic foot ulcers is the first in a series of six articles which will cover all the major dressing materials, highlighting the advantages and disadvantages of each from the available research evidence.
Publisher’s note
Figures 1-3 are not available in the online version.
