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Appropriate use of larval debridement therapy in diabetic foot management: consensus recommendations

Recent evidence shows that larval debridement therapy (LDT) is a cost-effective, highly selective method of rapidly debriding diabetic foot ulcers (DFUs). Despite this, it is largely considered an adjunctive treatment or debridement method of last resort. A working group of key opinion leaders in diabetic foot care proposes that LDT should be considered alongside other debridement methods for DFUs and, when appropriate, be initiated early in the wound management process as part of an integrated care plan. The group’s consensus recommendations for appropriate selection and use of LDT in this context are presented here. 

Larval debridement therapy (LDT) is an established method of rapidly and effectively debriding and treating diabetic foot ulcers (DFUs; Sherman, 2014). It is suitable for a wide range of patients, including those considered too fragile for surgery (Gottrup and Jorgensen, 2011; Gilead et al, 2012). Studies show that LDT is associated with faster healing rates (Sherman, 2003; Armstrong et al, 2005; Tian et al, 2013), reduced amputation rates (Armstrong et al, 2005; Paul et al, 2009; Gottrup and Jorgensen, 2011) and reduced need for antibiotics (Armstrong et al, 2005; Paul et al, 2009), compared with other conventional debridement methods in patients with DFUs.

Despite the evidence, LDT is largely considered an adjunct to other debridement options, an interim measure by practitioners without training in sharp debridement or a last resort in non-healing wounds resistant to other debridement methods (Evans, 1997). LDT targets devitalised tissue and may salvage healthy adjacent tissue. It may therefore be used in preference to sharp debridement in selected patients.

In November 2014, a working group of key opinion leaders in diabetic foot care met at the Wounds UK conference in Harrogate to discuss the consideration of LDT as a first-line debridement option, alongside other debridement methods, to be initiated early in the wound management process. This paper presents the group’s consensus recommendations for the appropriate selection and use of LDT in DFUs.

What is LDT?
LDT uses larvae of the greenbottle blowfly (Lucilia sericata) to remove dead tissue, cellular debris and exudate present in moist, sloughy wounds (Gottrup and Jorgensen, 2011). The larvae break down this material by physical actions and by excreting proteolytic digestive enzymes. They ingest the resulting liquified substrate, including any bacteria it contains. The larvae may be applied in bagged (Figure 1a) or free-range form (Figure 1b), depending on wound characteristics and patient preference (All Wales Tissue Viability Nurse Forum [AWTVNF], 2013).

Indications for use
In a wound that requires rapid debridement of devitalised tissue that is delaying wound healing, consideration should be given to using LDT first-line, either as a stand-alone option or alongside other debridement methods (i.e. sharp, surgical, mechanical, hydrosurgical and ultrasonic). When deciding whether LDT is appropriate, practitioners should take into account wound factors and then patient factors (Tables 1 and 2), along with cost considerations.

The decision to use LDT should be independent of wound site or depth. The larvae can tolerate direct pressure from a plantar wound if care is taken when packing the dressing and the wound is mostly offloaded. They can also withstand some submersion and may, therefore, be used on highly exuding wounds if measures are taken to avoid an occlusive environment, as they cannot survive lack of oxygen, such as frequent dressing changes and non-occlusive outer dressings.

Competencies for using LDT
Approval to administer LDT should be given by an appropriate advanced practitioner in consultation with the multidisciplinary team/foot protection service, according to local policy. However, subsequent application and management of LDT may be carried out by any qualified practitioner who has reached an appropriate level of competency through training and who has adequate clinical support. To ensure cost-effective use of LDT, these principles should be incorporated into your local diabetic foot protocol.

Every healthcare professional is responsible for maintaining his/her competence. One useful training tool is the BioMonde online academy (Box 1). A competency framework for debridement, outlining the skills and knowledge necessary to care for patients with DFUs, is given in Table 3.

Achieving optimal outcomes
As with other methods of debridement, LDT should be used as part of an integrated care plan involving effective pressure relief, infection control, revascularisation, glycaemic control and patient education (Waniczek et al, 2013).

The rationale for using LDT should be documented in the patient’s record and evaluated at each dressing change as part of an overall management plan.

Assessment
Before starting LDT, a holistic assessment should be undertaken by a qualified practitioner within the multidisciplinary foot clinic according to local policy and should include (AWTVNF, 2013):

  • A full assessment of the patient, wound type and wound bed. This should be undertaken and the results documented prior to LDT, taking into account:
    – Ability to offload pressure
    – Results of vascular studies
  • Patient consent
    – Provide simple, clearly written information about the nature, risks and benefits of treatment
    – Informed verbal consent should be obtained and documented where appropriate
    – If this is not possible (e.g. due to lack of capacity), practitioners should follow local guidance
  • Information on LDT for patients and carers.

Wounds treated with LDT have a distinctive odour and this should be discussed with patients before the start of treatment to improve adherence.

Applying LDT
The aim of debridement is to achieve a clean, granulating wound bed. More than one consecutive application may be necessary to attain this goal. The process described below should be carried out with the support of an appropriate advanced practitioner in the context of the multidisciplinary team to ensure all aspects of care are being addressed.

Each application of larvae (whether bagged or free-range) can be left in place for up to four days before removal. Outer dressings should be checked or changed daily (viable larvae are indicated by movement and the presence of a dark red exudate). At day three, the wound should be reviewed and the expected healing trajectory assessed. If a further application is needed, reordering the larvae at this point will allow treatment to continue without a break (Figure 2).

The consensus group agreed that if LDT is applied correctly, most wounds are effectively debrided after two or three applications. If more than three applications are judged necessary, practitioners should consider whether other factors (e.g. infection) are affecting healing, whether LDT is being applied correctly and whether another debridement method is needed.

LDT should be stopped once the wound bed appears clean and granulating. If the wound re-sloughs, a thorough review of the patient and wound should establish why this has occurred. Offloading and diabetes control should be optimised. Further applications of LDT can be considered using the principles described above.

It is important to note that once the slough and non-viable tissue is removed, the volume of the wound often increases. This is normal and not a cause for concern. The exudate during LDT will be a red/brown colour due to breakdown of tissue and this should not be confused with bleeding.

Antibiotics and antimicrobials
It is not necessary to stop systemic antibiotics before LDT. However, topical disinfectants, local anaesthetics and some hydrogels (i.e. those containing propylene glycol as a humectant and preservative) may have a negative effect on the growth and vitality of the larvae (AWTVNF, 2013). The wound should therefore be cleaned prior to LDT to remove any remnants that may remain.

Adjunctive therapies
For most patients, optimal outcomes will be seen if LDT is combined with sharp or surgical debridement to debulk the wound and remove any callus border. This will give the larvae better access. LDT can, however, be applied directly to the wound if sharp debridement is not appropriate (e.g. patients with pain and those unfit for surgery). Where sharp debridement alone is selected as the first-line measure, consider LDT subsequently if a level of slough remains that would delay wound healing.

Other benefits of LDT
As well as providing a rapid and effective method of debridement, evidence is emerging that LDT is associated with secondary wound healing benefits (Box 2). These include:

  • Possible antimicrobial effects (through ingestion of bacteria and excretion of antimicrobial substances; Andersen et al, 2010; Nigam, 2013; Cerovksy and Bem, 2014)
  • Reduction in resistance to antimicrobials (Bexfield et al, 2010)
  • Enhancement of treatment with systemic antibiotics (van der Plas et al, 2010)
  • Possible promotion of tissue regeneration and restoration of normal wound healing processes (via excretion of active chemicals; Nigam, 2013)
  • Possible role in biofilm disruption and formation (Nigam, 2013)
  • Possible analgesic properties (AWTVNF, 2013).

Wound management following LDT
Effective debridement with LDT is not an endpoint, but part of the continuum of treatment. It is vital to maintain the healing momentum after debridement by continuing to follow the principles of wound bed preparation and good moist wound healing. LDT may be used in conjunction with interventions such as prior to negative pressure wound therapy. It is important that any decision about a wound involves a process of objective setting, assessment, documentation, evaluation and review (Figures 3 and 4).

Cost-effectiveness
The factors that impact on the cost of the different debridement methods are not confined to the cost of the materials alone, but include (AWTVNF, 2013):

  • Unit cost of treatment
  • Length of treatment
  • Number of procedures required
  • Cost and likelihood of infection
  • Cost and likelihood of adverse events.

An evaluation carried out at the Swansea Centre for Health Economics at the University of Swansea across a range of wound types found that LDT is cost-effective when compared with other debridement methods including surgical, sharp, mechanical and autolytic interventions (Bennett et al, 2013).

Conclusion
LDT is a cost-effective, highly selective method of rapidly debriding a wide range of DFUs. As such, it may be considered as a first-line debridement option and, when appropriate, initiated early in the wound management process to achieve optimal results. Selection, application and ongoing management of LDT should be carried out in the context of the multidisciplinary team/foot protection service, with initial approval to administer given by an appropriate advanced practitioner according to local policy.

New evidence is emerging that LDT has secondary antimicrobial effects. If borne out in further studies, LDT may have a future role as part of an antimicrobial strategy to reduce reliance on antibiotics.

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