Chronic wounds represent a huge burden to patients who live with them, as well as a significant financial drain on healthcare systems. According to the most recent Burden of Wound Care study, which examines the prevalence of wounds in the UK and the cost to the NHS of treating them, the annual spend on wound management hit £8.3bn in 2017–18, a real-terms increase of 48% since 2012–13.

In England, the prescription costs of advanced and antimicrobial wound dressings in primary care alone exceeded £110m in 2015. However, not all advanced dressings are created equal: in some cases, a type of dressing might constitute a small proportion of the total items supplied, but a far higher proportion of the total cost. Silver dressings are a case in point. They made up less than 10% of items prescribed but comprised more than 18% of the cost.

Even so, wound care products themselves are just a small cog in a much larger wheel, accounting for as little as 12–15% of the financial burden of wound management. It’s clinical time that strains budgets, making up 80% of the total cost. Already, higher-priced dressings are most often used on wounds that are slow to heal, and spending a little more on products that make treatment and management more effective has the potential to save health services money and resources, as well as improving patient outcomes.

As such, when choosing the most appropriate dressing for a wound, focusing on purchase price is short-sighted and can potentially end up costing more. For example, a cheaper dressing might be less effective, delay healing and need to be changed more frequently. In acute settings, this could mean patients spend longer in hospital, making their care more expensive and potentially riskier than it would be otherwise.

Biologic wound dressings in particular are designed to help restore patients’ interrupted wound repair mechanisms. They comprise active biological agents with antimicrobial (including honey, silver and iodine), antioxidant (like N-acetylcysteine, curcurmin or hyaluronan) or anti-inflammatory attributes (such as hydrocolloid, hydrogel or foam dressings).

These attributes help prevent the loss of heat, protein, electrolytes and water from the wound, as well as lowering the risk of contamination. They also promote wound debridement through autolysis – the breakdown of cells or tissues by their own enzymes – and create a granular wound bed, the presence of which indicates the wound is progressing from the inflammatory to the proliferative healing phase.

The right choice

While some dressings release the biological agent into the wound – like those containing silver and honey – others work by absorbing bacteria from it first. However, for these high-tech dressings to make a difference, clinicians need to understand when and where to use them. Alison Schofield, tissue viability team lead and clinical nurse specialist at North Lincolnshire and Goole NHS Foundation Trust, explains that the first thing to consider when choosing a dressing is wound assessment. “As specialists in wound care, we have the knowledge and expertise to be able to apply the best practice guidance, and to educate general clinical staff on what to look for,” she says.

According to the 2016 National Institute of Health and Care Excellence (NICE) ‘Chronic wounds: advanced wound dressings and antimicrobial dressings’ evidence summary, the factors that should be considered when selecting a dressing include the stage of wound healing, the amount of exudate, the presence of an infection and the wound odour.

But wound care is about more than the wound itself. It’s also important to consider a dressing’s adhesiveness and ease of removal, as well as the potential for the adhesive to cause irritation. Absorption, ease of use, protection of the surrounding skin, and the frequency and discomfort of dressing changes are also important factors, as, of course, is patient preference. Schofield explains that the TIMES principle is typically used to help decide whether a biologic dressing is appropriate for a particular patient –and wound. The acronym was coined to summarise clinical considerations in effective wound bed preparation and stands for tissue, infection/inflammation, moisture, edge of wound and surrounding skin.

Useful as it may be, the TIMES protocol is not an exact science, so it relies heavily on the clinician’s expertise. The British National Formulary (BNF) gives further guidance on how to match infection characteristics to specific biological wound care products. As such, it advises that a topical antimicrobial dressing can be used to reduce bacteria levels at the wound surface but that won’t stop an infection that’s spreading. It also notes that medical-grade honey can be used if antimicrobial and anti-inflammatory properties are indicated, while iodine dressings can be used to treat clinically infected wounds. Dressings containing silver should only be used when clinical signs or symptoms of infection are present. Dressings containing other antimicrobials, like polihexanide or bacteria-binding dialkylcarbamoyl chloride, can be used on wounds in a similar way.

Weighing up

As the BNF guidance suggests, though evidence of local wound infection can help guide clinicians in their choice of treatment, it is far from a simple measure. Infections progress along a scale from mild to severe, with clinical signs and symptoms changing accordingly.

This progression is represented by a five-stage ‘infection continuum’ that runs from contamination and colonisation through to local infection, where topical antimicrobials become necessary, all the way to spreading and systemic infections, when systemic antimicrobials are also needed.

That’s not all. Clinicians must consider a range of other factors in deciding treatment pathways and appropriate dressings. “We look at the patient’s history and use a holistic approach because it’s important to consider risk factors,” Schofield says.

“For example, a diabetic patient with a foot wound might also have neuropathy and have no feeling in their feet. So, they will likely not display signs of infection in the same way as other patients. As a clinician, I would weigh up whether it’s better to use antimicrobial dressings as a preventative measure, or to wait until there are overt signs of infection.”

Antimicrobial stewardship is a growing priority in healthcare settings, so the expertise of clinical specialists like tissue viability nurses (TVNs) increasingly comes into play when biologic dressings are an option. Work on understanding antimicrobial resistance and stewardship in the context of wound management is ongoing.

That work is made more difficult because dressings are typically classified as medical devices, so there is often a lower evidence-quality threshold for their approval than for medicines. As a result, randomised controlled trials (RCTs) of these products tend to be of poorer quality, and it is argued that NHS procurement fails to give adequate weight to other types of evidence, including that gathered during product assessment, as well as evidence and recommendations from expert groups.

Local and national variations in procurement practices, formularies and treatment frameworks contribute to wide disparities in services and care. With so many knowledge gaps, the expertise of TVNs is particularly important in assisting with dressing selection.

The National Wound Care Strategy Programme (NWCSP) is working towards developing a national strategy for wound care across England to address disparities and support clinicians, focusing on limb ulcers and wounds.

It has produced recommendations for healthcare professionals drawing on evidence from recognised, widely used sources like NICE, Public Health England and the WHO. Interestingly, according to the NWCSP, there is no definitive evidence favouring a particular type of dressing type over another for lower limb wounds, or to manage surgical wounds and prevent infection at the wound site. If anything, that makes the expertise of individual TVNs and doctors even more important.

“Tissue viability nurse specialists have the knowledge and access to all the best-practice statements, consensus documents and published guidance,” Schofield concludes. “The ultimate decision is the clinician’s, whose individual preference will be based on their own experience and patient feedback.”

The TIMES principle

T – Tissue The overall appearance of the wound bed is key in determining how healthy the tissue is and whether debridement is required. Devitalised tissue encourages microbial growth and should be removed.

I – Infection/inflammation Bacteria can multiply and cause infection, slowing healing and increasing pain and exudate. In the absence of clear infection, biofilm can also delay healing.

M – Moisture If excessive or, conversely, deficient moisture levels are evident, moisture balance may be needed to protect the skin surrounding the wound and optimise healing.

E – Edge of wound Rolled edges around a wound, or lack of new, healthy tissue at the wound edge suggests impaired healing.

S – Surrounding skin Examination of the skin surrounding the wound is important in the management strategy; addressing its condition can minimise the potential for infection and inflammation.

The five-stage infection continuum

Stage 1: Contamination All wounds have micro-organisms, which will not grow and proliferate in an nonconducive environment.

Stage 2: Colonisation Micro-organisms successfully grow and divide but they don’t cause wound infection or any harm.

During the first and second stages, no antimicrobials are required but vigilance is recommended.

Stage 3: Local infection Covert and overt signs and symptoms occur in and around the wound. Early intervention is crucial and topical antimicrobials are indicated.

Stage 4: Spreading infection Worsening local symptoms and more general signs of wider infection develop.

Stage 5: Systemic infection The original infection spreads through the whole body, and can lead to sepsis, organ damage and death.

During the fourth and fifth stages, systemic and topical antimicrobials are needed.