Interventions in infected venous leg ulceration in clinical practice

Any breach of the skin, such as a wound, will cause bacteria to develop as a result of being open and exposed to the elements for a long time (Barrett, 2017). Venous leg ulcers, like all chronic wounds with a long healing time, are at risk of developing wound infection. Careful observation and a timely response to subtle signs can prevent a systemic wound infection developing. In order to achieve this, it is helpful for health professionals to be familiar with the continuum of wound infection and to be able to intervene appropriately before a systemic wound infection develops.

Overview of the continuum of infection in chronic wounds

Contamination

Contamination is when microbes (bacteria and fungi) are present, but at levels that are not causing any problems with the wound. No treatment is necessary but frequent observation and on-going reassessment is required (Edwards-Jones and Flanagan, 2013; International Wound Infection Institute (IWII), 2016).

Colonisation

The next stage is known as colonisation and this is where the micro-organisms start to multiply, but still at relatively low levels. This level of micro-organisms will not trigger a response from the host (patient) and there will be no signs or effect on the wound healing (World Union of Wound Healing Societies (WUWHS), 2008). Again, no active treatment is required, only careful monitoring.

Local wound infection

Once the microorganisms start to multiply rapidly, the wound is now at risk of developing an infection if the levels of micro-organisms are not controlled (Brown, 2018). This stage used to be referred to as ‘critical colonisation’; however, more recently it has been renamed ‘local infection’. During this phase, there may only be subtle wound-related signs, including over-granulation, the tissue easily bleeding, an increase in malodour, stalled healing and the wound may even start to break down (IWII, 2016). In addition to these covert signs, there may be the more obvious, classic signs of local infection present, such as erythema, local warmth, swelling, purulent discharge, increased malodour and an increase in pain (Gardner et al, 2001).

These signs indicate that the level of bacteria in the wound is very high and, if not reduced, a local or systemic wound infection is likely to develop. An additional feature that contributes to the high bacterial burden in a wound is the presence of biofilms (Wolcott and Rhoads, 2008).

Biofilms

A biofilm is defined by Wolcott and Rhoads (2008) as a dynamic community of bacteria and fungi living in a protective self-secreted matrix of sugars and proteins which becomes attached to the wound bed (Figure 1). These are resistant to antibiotic therapy and will continue to remain in the wound if not effectively removed (Wounds UK, 2017). It has been suggested that biofilms present as a ‘shiny’, ‘slimy’ or ‘translucent’ layer on the surface of a non-healing wound (Lenselink and Andriessen, 2011; Hurlow and Bowler, 2009). However, the ability to see a biofilm in a wound is under debate and there is a consensus that biofilms are generally not visible to the naked eye (White and Cutting, 2012; WUWHS, 20008). As a result, there are innovations under development that may make biofilms easier for clinicians to detect (Nakagami et al, 2017). Although it is not possible to say whether the presence of biofilms will result in wound infection, there is no doubt that they may delay healing (Cooper et al, 2014). A Wounds UK (2017) consensus document suggests that the following signs should lead the health professional to suspect that the presence of a biofilm may be contributing to the delay in healing:

• Delayed healing despite the implementation of good wound care and management of contributing comorbidities
• Inconclusive wound swab result and/or failure to respond to antibiotic therapy
• Signs of local infection – this may be more than 30 days' duration
• Poor granulation tissue
• Increased exudate
• Slough and necrotic tissue in the wound that reforms rapidly post-debridement (Keast et al, 2014; Metcalf et al, 2014; Percival et al, 2015; IWII, 2016).

Figure 1. An ulcer with a suspected biofilm. Note the shiny, slimy surface of the wound

Managing wound infection in venous leg ulceration

As venous leg ulcers often take several weeks or even months to heal, they are at risk of developing wound infections (Barrett, 2017; National Institute for Health and Care Excellence (NICE), 2019) In addition, the standard practice of leaving compression bandage changes for up to a week, in simple, uncomplicated ulcers, may provide a warm and ideal environment for bacteria to multiply. Therefore, health professionals need to be vigilant and assess the condition of the ulcer at every dressing change.

Contamination and colonisation with bacteria will be inevitable due to the duration of the wound and at these stages, healing will generally not be delayed (Edwards-Jones and Flanagan, 2013). However, if there are signs that the level of microbes is rapidly increasing, treatment is required to prevent the infection spreading and developing into full systemic infection (Edwards-Jones and Flanagan, 2013). Table 1 outlines the signs and symptoms of local wound infection.

Interventions to reduce the bacterial burden

Managing an elevated bacterial burden in a venous leg ulcer is necessary to prevent the infection spreading or progressing to a systemic wound infection (Hewish, 2014). The aim at this stage is to reduce the volume of microbes in the ulcer and the use of a combination of topical antiseptic solutions and antimicrobial dressings is recommended (IWII, 2016).

Antimicrobial treatments: antiseptic solutions

Antiseptic solutions are skin disinfectants with broad spectrum antibacterial, antiviral and antifungal activity and are used for cleaning or irrigating infected wounds or wounds with a high bacterial burden (Figure 2) (IWII, 2016).

Figure 2. Ulcers with spreading infection that require systemic antibiotics as well as antimicrobial products

In the past, the routine use of antiseptic solutions was not recommended due to concerns over toxicity and their potential effect on the healing process (Schultz et al, 2003). As a result, their use became a controversial area in wound care and they were rarely used (Drosou et al, 2003). More recently however, in light of concerns over the often-inappropriate over-prescribing of systemic antibiotics and the introduction of antimicrobial stewardship (NICE, 2015), their use is becoming more popular for cleaning wounds suspected of having a high bacterial burden.

Some of the antiseptics on the market include polyhexamethylene biguanide (PHMB), povidone iodine (PVD-1) and octenidine dihydrochloride. Until recently, the effectiveness of iodine in wound care had been debated due to concerns around toxicity and the potential for delayed granulation tissue development (Sibbald and Elliott, 2016). In 2016, studies, including a systematic review conducted by Vermeulen et al (2010) and Sibbald and Elliott (2016), concluded that iodine-based products were safe to use, with no significant adverse side effects and were not inferior to any other antiseptic product. A randomised controlled trial (Bellingeri et al, 2016) found that the PHMB solution debrided wounds, reduced inflammation and accelerated wound healing.

In clinical studies, octenidine used on venous leg ulcers was found to be an effective and safe antiseptic solution (Hübner et al, 2010; Vanscheidt et al, 2012) and antiseptic solutions are now recommended as a first-line treatment of heavily colonised wounds (Bellingeri et al, 2016; IWII, 2016), although their use should be monitored and re-assessed after 2 weeks (Wounds UK, 2017). Table 2 outlines the three main antiseptic solutions and their modes of action.

Antiseptic solutions for venous leg ulceration

Best practice in the community is to wash the patient's legs in potable, warm tap water if the home circumstances allow for it – a plastic-lined bucket is generally used for this. If the patient has bilateral ulceration, each leg should be washed in separate buckets or the water changed if the same bucket is used for both legs. Once the leg has been washed and patted dry, the antiseptic solution of choice should be applied directly to the ulcer using a clean, dampened swab and held in place for a minimum of 5 minutes, as per the manufacturer's instructions. It is not necessary to dry the ulcer.

Ideally, this should be done three times a week; however, this is dependent on the frequency of dressing changes (Vanscheidt et al, 2012). The ulcer can then be dressed with a suitable antimicrobial dressing (Schultz et al, 2003; Wounds UK, 2017). It is recommended that the ulcer is assessed at each dressing change and/or after 2 weeks of use for signs that the bacterial burden has reduced (Wounds UK, 2017). If this is the case, discontinuing the irrigation with the antiseptic solution should be considered. If the signs of local infection are still evident but the wound is starting to improve, the further use of the solution for a further 2 weeks can be justified (Wounds UK, 2017).

Antimicrobial treatments for high bacterial burden or local infection

When a high bacterial burden in a chronic wound, such as venous leg ulceration, is suspected because some of the signs outlined in Table 1 are visible, routine wound swabbing is no longer recommended to diagnose the bacteria present (Edwards-Jones and Flanagan, 2013). This is because of the unnecessary cost incurred in wound swabbing and culture in a laboratory, and, as this is a chronic wound, a high level of bacteria will inevitably be present and the result may be inconclusive (Edwards-Jones and Flanagan, 2013).

Due to ongoing concerns about the over-prescribing of unnecessary systemic antibiotics and bacterial resistance, current practice is to reduce the bacterial burden with the use of antiseptic and antimicrobial product; however, it may be necessary to use these products in combination with systemic antibiotics if the infection is severe and persistent (Edwards-Jones and Flanagan, 2013). Furthermore, systemic antibiotics are unable to treat biofilms as these are very efficient in developing resistance by forming a slimy casing through which the antibiotics cannot penetrate (Edwards-Jones and Flanagan, 2013).

In addition to irrigation with an antiseptic solution, it is recommended to use antimicrobial dressings containing, honey, silver, iodine or PHMB (Wounds UK, 2017). There are many different types on the market and choice will depend on presenting wound bed conditions, such as slough, exudate levels and location. Patient acceptability and unit cost are also important considerations, as they tend to be expensive to use and many Trusts offer guidance on product selection in wound care formularies as a result. The time-frame for ensuring appropriate usage of microbial dressings is the same as for the antiseptic solutions.

Managing suspected biofilms in wounds

Wounds UK (2017) proposes a ‘2-week challenge’ for when a suspected biofilm is the cause of the wound not healing as expected. The use of an antiseptic solution and an antimicrobial dressing is not enough to disrupt a biofilm (Wounds UK, 2017). The only way to disrupt a biofilm is by mechanically debriding it (Wolcott and Rhoads, 2008). If the health professional is not qualified to debride the wound surgically or to use sharp instruments, a monofilament fibre debridement pad, such as Debrisoft, Prontosan debridement pad or UCS Debridement is a useful way to disrupt the biofilm. Wounds UK (2017) suggests the following regime to disrupt the biofilm and enable to wound to progress to healing (Box 1). The purpose of this is to allow the antimicrobial treatments to have maximum effect on the bacteria in the very short window of opportunity between disruption of the biofilm and the re-appearance of the biofilms (Wounds UK, 2017).

Box 1.Regime to disrupt biofilmWeek 1

• Change the dressings a minimum of three times during the week and use a debridement pad at each dressing change
• Use a topical antiseptic solution and a suitable dressing or an antimicrobial dressing
• It may be necessary to do this more frequently, depending on the state of the wound and exudate levels

Week 2

• Change the dressings a minimum of two times during the week and use a debridement pad at each dressing change
• Use a topical antiseptic solution and a suitable dressing or an antimicrobial dressing
• It may be necessary to do this more frequently, depending on the state of the wound and exudate levels

Wounds UK (2017)

The condition of the wound should then be re-assessed. If improved, discontinue the use of antiseptic/antimicrobial products and revert to previous (non-antimicrobial) dressing regime. If no improvement is noted, it is recommended that the 2-week challenge should be repeated, using different types or combinations of antimicrobial products. After another 2 weeks, if no improvement is noted, Wounds UK (2017) recommends that a specialist opinion may be needed.

Managing spreading or systemic wound infection

A wound swab for laboratory analysis should be taken if the patient is displaying the signs of spreading or systemic infection, such as:

• Cellulitis
• Pyrexia
• Increased pain
• Lymphangitis
• Deep wound infection
• Bone involvement
• Wound infection plus systemic signs of sepsis or bacteraemia
• Enlarging wound (Public Heath England, 2014).

The wound should be cleaned with tap water or saline to remove surface necrotic tissue and slough and the swab should be taken using the rotation or zigzag method (Edwards-Jones and Flanagan, 2013). Ideally, the swab should be taken before antibiotics are commenced; however, health professionals need to use their clinical judgement as to whether it is appropriate to withhold treatment until the results are known (Brown, 2015).

Even though the patient is taking systemic antibiotics – particularly in the case of spreading infection including cellulitis and lymphangitis or exhibiting symptoms of sepsis and bacteraemia – it is recommended that antiseptic and antimicrobial products are used as an additional treatment (Edwards-Jones and Flanagan, 2013).

It is not necessary to discontinue compression therapy in the presence of a high-bacterial burden or spreading wound infection; however, the patient may not be able to tolerate this as the ulcer may be too painful. In addition, if daily dressing changes are required until the infection resolves, it may not be practical to reapply compression bandages daily. Once the infection has been treated, compression therapy can be implemented again. However, the decision to discontinue compression when the ulcer is infected must be assessed on a case-by-case basis and is dependent on the patient's tolerance.

Sepsis

Practice nurses must familiarise themselves with the signs of sepsis. Sepsis is a severe inflammatory response to bacteria or other micro-organisms, and it can be life-threatening. The general symptoms of sepsis include chills, confusion or delirium, an elevated or low temperature (hypothermia), low blood pressure resulting in dizziness, tachycardia, elevated respiratory rate shivering or shaking, skin rash or mottled skin, and warm skin. The patients most at risk of developing sepsis are the very young or very old, patients with chronic conditions, such as diabetes and cancer, and those who have an impaired immune system. These risk factors are exacerbated when combined with the presence of a severe infection in the bloodstream, bowel, kidneys, lungs, brain and the skin, for example, cellulitis or infected wounds (NHS, 2019; Sepsis Alliance 2019). The treatment for sepsis is hospital admission with systemic antibiotics (usually intravenously administered), intravenous fluids and oxygen therapy (NHS, 2019). In addition, the patient will undergo blood cultures and monitoring of their kidney function.

Sepsis can be a fatal condition if not treated immediately and six in every ten cases will die if septic shock develops (NHS, 2019). However, sepsis is treatable if it is identified and treated quickly and, in most cases, the patient will fully recover with no lasting problems. Many patients with venous leg ulceration will fall into these risk factors and practice nurses must be vigilant when assessing patients who present with a severe wound infection.

Conclusion

This article has outlined the wound infection continuum to ensure that health professionals are familiar with the visual cues and symptoms and are able to intervene using antimicrobial products to prevent a full infection developing. The management of a wound with a high bacterial burden, biofilms, local and systemic infection has been outlined together with suggestions on their management in patients with venous leg ulceration.

KEY POINTS

• Venous leg ulcers are chronic wounds, which makes them susceptible to wound infection
• The signs of a developing infection are subtle and practice nurses must be familiar with them and to be observant
• The routine use of systemic antibiotics is no longer recommended in chronic wounds
• Guidance on managing wound infection in venous ulcers is highlighted
• Practice nurses must also be vigilant to the signs of sepsis which can develop from chronic wound infection

CPD reflective practice

• Would you be able to recognise the signs of an increasing bacterial burden in a venous leg ulcer and differentiate between this and a systemic infection?
• Are you familiar with the guidance on the appropriate prescribing of systemic antibiotics in wound care?
• What is the current guidance is on the use of topical antiseptic and antimicrobial products and how they work?