Chronic wounds: advanced wound dressings and antimicrobial dressings

The 2015 NICE guideline on preventing and managing diabetic foot problems found that evidence surrounding different types of dressings for diabetic foot ulcers was generally of low or very low quality and often limited or inconclusive. The guideline recommends wound dressings (type not specified) as an option for managing diabetic foot ulcers, alongside a range of other options provided by a multidisciplinary team. When deciding about wound dressings and other options, the clinical assessment of the wound and the person's preference should be taken into account, and dressings with the lowest acquisition cost appropriate to the clinical circumstances should be used.

A Cochrane overview (Wu et al. 2015; 17 randomised controlled trials [RCTs], total number of participants unclear) also concluded that there is currently no robust evidence that any advanced dressing type is more effective than basic wound contact dressings for healing foot ulcers in people with diabetes. Few RCTs were available for each comparison and they generally had small numbers of participants. When direct evidence of a difference was reported, the evidence was considered to be low or very low quality. Therefore, the findings are reported to be uncertain and not optimal in terms of informing practice. The authors concluded that practitioners may want to consider the unit cost of dressings, their management properties and the person's preference when choosing dressings.

See the full evidence review on diabetic foot ulcers for more information.

The NICE guideline on preventing and managing pressure ulcers found that, overall, the quality of clinical evidence for wound dressings was low to very low because most of the studies had very serious limitations. No recommendations could be made about using specific types of dressings, except that gauze dressings should not be used for pressure ulcers. The NICE guideline development group emphasised that the effectiveness of each dressing would depend on the type of pressure ulcer and, therefore, chose to recommend a dressing that promotes the optimum healing environment, rather than a specific type of dressing. NICE advises that clinicians should discuss the type of dressing with the person with the pressure ulcer and, if appropriate, their family or carers, taking into account the person's pain and tolerance, the position of the ulcer, the amount of exudate and the frequency of dressing change. A dressing that promotes a warm, moist wound healing environment should be considered for grade 2, 3 and 4 pressure ulcers.

Two Cochrane reviews on advanced wound dressings for treating pressure ulcers have been published. The first review (Dumville et al. 2015a) (11 RCTs, n=523) found there was no evidence of a difference between hydrogel and other dressings in terms of complete wound healing or adverse events (low‑ or very low‑quality evidence). The second review (Dumville et al. 2015b) (6 RCTs, n=336) found no evidence of a difference between alginate dressings and alternative treatments in complete wound healing (very low‑quality evidence). The RCTs included in both Cochrane reviews were small and considered to be statistically underpowered to detect treatment differences, should they exist. Also, they had short follow‑up times (3 to 12 weeks) and were at risk of bias. The implications for practice are therefore unclear. The authors noted that healthcare professionals may wish to consider other characteristics such as costs and wound management properties when choosing between dressings.

A meta‑analysis by Huang et al. (2015) (35 RCTs or quasi‑RCTs, n=5,401) on dressings for preventing pressure ulcers found that compared with standard care alone, the risk of developing pressure ulcers was reduced in people who used hydrocolloid dressings, foam and film dressings. Fewer people in the foam dressings group developed pressure ulcers compared with the hydrocolloid dressings group. However, although the authors stated that the methodological quality of the included studies was assessed using the Cochrane Collaboration tool and the risk of bias is reported, the quality of the evidence is not graded. They noted that the included trials have many limitations and stressed that dressings do not replace best practices, such as turning and repositioning, skin care, good nutrition and continence management. In people who are at risk of pressure ulcers, NICE guidance on preventing and managing pressure ulcers recommends repositioning, ensuring nutrition and hydration are adequate, using pressure redistribution devices and considering barrier creams for preventing pressure ulcers.

See the full evidence review on pressure ulcers for more information.

SIGN guidance on the management of chronic venous leg ulcers (published in 2010; accredited by NICE) advises that simple non‑adherent dressings and high compression multicomponent bandaging should be used for treating venous leg ulcers. Silver and honey dressings should not be used routinely. Graduated compression hosiery is recommended to prevent recurrence of venous leg ulcers. The evidence that the SIGN recommendations were based on is updated by the evidence outlined below.

Three Cochrane reviews have considered wound dressings for healing venous leg ulcers. The first review (O'Meara et al. 2015) (5 RCTs, n=295) found no differences between different alginate dressings, or between alginate dressings and hydrocolloid dressings, or alginate dressings and non‑adherent dressings. The second review (O'Meara and Martyn-St James 2013) (12 RCTs, n=1,023) found no differences between foam dressings and a variety of other primary wound contact dressings when applied beneath compression systems. The RCTs included in these 2 Cochrane reviews were considered at high or unclear risk of bias and the quality of the evidence was generally reported to be low or very low quality. The authors concluded that good‑quality evidence from well‑designed RCTs is needed before definitive conclusions about the efficacy of alginate or foam dressings for managing venous leg ulcers can be drawn and recommendations about their use can be made.

No trials were identified comparing different dressings for relieving pain in venous leg ulceration in the third Cochrane review (Briggs et al. 2012). Foam dressings containing ibuprofen (2 RCTs, n=470) did appear to provide pain relief for some people with painful venous leg ulcers compared with best practice or non‑medicated foam dressings. However, the authors of the Cochrane review noted that the studies have methodological limitations that make interpreting the evidence difficult. Also, the release of ibuprofen into the wound bed depends on the presence of wound exudate and therefore these dressings are not suitable for people with venous leg ulcers that have low levels of, or no, exudate.

The Agency for Healthcare Research and Quality (2014) (AHRQ) in the USA considered the benefits and harms of dressings that regulate wound moisture in people with chronic venous leg ulcers. In terms of the proportion of ulcers healed, no differences were found between the groups for comparisons including advanced wound dressings (film, alginate and antimicrobial dressings, including silver dressings). Definitive conclusions could not be drawn for many comparisons because of limitations in study quality, imprecise estimates and heterogeneity in study designs. Also, conclusions about the effects of advanced wound dressings on pain or quality of life could not be made due to inconsistent reporting of these outcomes. The AHRQ stated that there was a general lack of well‑designed, well‑controlled studies, as well as lack of a standard case definition, or approaches to managing confounders and interactions. For advanced wound dressings, there was no impact on wound healing when compared with compression therapy alone.

A meta‑analysis of 2 RCTs (n=255) of silver dressings for venous leg ulcers by Greer et al. (2013), which were assessed as fair quality by the authors, found that there was no difference between silver dressings and non‑silver dressings. A second study by Leaper et al. (2013) (4 RCTs, n=1,055) found that, compared with control (foam or alginate dressings, or local best practice including passive and non‑antimicrobial dressings), a specific brand of silver dressings reduced ulcer area over 4 weeks in people with hard‑to‑heal venous leg ulcers.However, this meta‑analysis has many limitations that affect its interpretation. For example, it did not report the quality of the evidence or assess the risk of bias, complete data were not reported for all outcomes, only 1 brand of silver dressing was assessed and, as well as sponsoring the study, the manufacturer of that brand of dressing was involved in authoring the paper.

Economic modelling of data from 1 of the RCTs in the meta‑analyses (the VULCAN trial [Michaels et al. 2009], n=213) found that silver dressings were associated with an incremental cost of £97.85 compared with control dressings when used for treating venous leg ulcers. The additional cost of silver dressings was partly due to an increased cost of dressings, but also due to a greater number of dressing changes in the silver dressings group. Although it was a pragmatic, publicly funded, well‑designed RCT that reflected standard practice at the time it was undertaken, this study (and its cost‑effectiveness analysis) has been criticised for its relevance and generalisation to everyday clinical care; for example, participants did not necessarily have wounds that were infected or were at high risk of becoming infected (Gottrup and Apelqvist 2010).

A more recent study by Jemec et al. (2014) used data from the meta‑analysis by Leaper et al. (2013) and estimated that the initial 4 weeks' treatment in primary care was about £90 more expensive for the group treated with silver dressings compared with non‑silver dressings. However, because of a shorter time to wound healing and less need for referral for specialist care, the average total treatment cost per person was about £140 lower for silver dressings compared with non‑silver dressings. It is unclear how the outcome time to wound healing was obtained from the outcomes presented by Leaper et al. (2013) (primarily reduced ulcer area). Also, the limitations of the study by Leaper et al. (2013) subsequently limit the quality of the cost‑effectiveness analysis and affect its application to practice.

See the full evidence review on venous leg ulcers for more information.

A Cochrane review (Forster and Pagnamenta 2015) found no studies on wound dressings that met the inclusion criteria.

See the full evidence review on arterial leg ulcers for more information.

A meta‑analysis by Carter et al. (2010) (10 RCTs, n=1,356) found no difference between silver dressings and control dressings in complete healing of leg wounds and ulcers, although reduction in wound size was greater with silver dressings in the short term. Measures of infection were not assessed. Although they noted that all of the RCTs on silver dressings had quality or bias issues, none were considered by the authors to be poor quality. However, this study assessed the quality of the evidence using an atypical approach. Also, the included RCTs had many limitations, including lack of blinding or allocation concealment, use of inappropriate analyses, incomplete reporting, lack of generalisability to real world populations, differences in baseline characteristics and loss of patients to follow‑up.

A Cochrane review (Storm-Versloot et al. 2010) on topical silver products (dressings or creams) for preventing wound infection identified 26 RCTs (n=2,066), 20 of which considered burns. Most of the trials were small and of poor quality, with many demonstrating a high or uncertain risk of bias. The authors considered that there was insufficient evidence to support the use of silver dressings or creams because, generally, they did not promote wound healing or prevent wound infections.

A Cochrane review by Jull et al. (2015) concluded that honey appeared to heal partial thickness burns (2 RCTs, n=992: high‑quality evidence) and infected post‑operative wounds (1 RCT, n=50: moderate‑quality evidence) more quickly than comparators. However, the comparators used may not be relevant to current practice (for example, paraffin gauze, sterile linen and gauze), reducing the relevance and generalisability of the results. Evidence for differences in the effects of honey and comparators when used for other wounds is of low or very low quality and does not form a robust basis for decision‑making.

A systematic review (Vermeulen et al. 2010) (27 RCTs, number of participants not reported) found that most RCTs showed no substantial differences in beneficial or adverse effects between iodine (mainly povidone or cadexomer iodine) and comparators when used for chronic and acute wounds, burn wounds, pressure sores and skin grafts. Overall, trial quality was limited. The authors concluded that iodine does not appear to be inferior to other antiseptic agents and does not impair wound healing. However, there is a need for high‑quality RCTs addressing the effectiveness and safety of iodine to treat or prevent wound infection, in order to clearly determine its place in present‑day wound care.

See the full evidence review on infected wounds for more information.

Dressings are generally classified as medical devices. The quality of the evidence required for approval of medical devices is generally lower than that required for medicines. This is reflected in the poor quality of many of the RCTs in this area.

Few RCTs were available for many of the comparisons considered in the systematic reviews and meta‑analyses. Limitations of the RCTs include poor design and reporting, high risk of bias, small sample sizes and imprecision, lack of blinding, use of inappropriate comparators, lack of clinically relevant outcomes and insufficient follow‑up.

The limitations of the RCTs, and subsequently the systematic reviews and meta‑analyses based on those RCTs, means that good‑quality evidence is available for few analyses of advanced wound dressings for managing chronic wounds. Overall, the clinical evidence is generally uncertain and not optimal in terms of informing clinical practice. Further good quality research is needed to improve confidence in the evidence, and is likely to change the existing evidence. Studies are also lacking on the cost effectiveness of advanced dressings for managing chronic wounds.

See the full evidence review on evidence strengths and limitations for more information.