Maggots mixed munching

1 November 2013

Does using maggots on sloughy ulcers make a positive difference?

CLINICAL BOTTOM LINE:

Using maggots on venous ulcers does not increase time to healing in sloughy wounds, although it may reduce the time to debridement, but with increased pain.

CLINICAL SCENARIO:

Presence of devitalised tissue on a wound bed is assumed to delay healing. Debridement has been encouraged, although there is little evidence that debridement in venous ulcers reduces healing time or increases healing rates. Suggested methods of debridement are mechanical, surgical, autolytic, and biological (larval). Autolytic is generally considered standard care as it does not require the specialist skill that surgical debridement does. Larval therapy has been suggested as an alternative and may be faster.

QUESTION:

Among patients with slow-to-heal venous ulcers, does larval therapy reduce time to healing compared to standard care?

SEARCH STRATEGY:

PubMed Clinical Queries (therapy, narrow): Maggots AND Ulcer

CITATION:

Dunville JC, Worthy G, Bland JM, et al. Larval therapy for leg ulcers (VenUS II): randomised controlled trial. BMJ 2009;338:b773. doi:10.1136/bmj.b773

STUDY SUMMARY:

Three-arm, parallel group, randomised controlled trial at 18 centres in the United Kingdom between July 2004 and May 2007. Patients were recruited from leg ulcer clinics, community nurse caseloads, hospital wards, and hospital outpatient departments. More than 1700 patients were screened and 267 were randomised. Inclusion criteria were presence of venous ulcer or mixed venous/arterial ulcer (ABI ≥ 0.6) with at least 25 per cent of the ulcer covered with slough. Patients were excluded if they were pregnant, lactating, allergic to hydrogel, had grossly oedematous legs, or were taking anticoagulants. If participants had more than one ulcer, the largest ulcer was used as the reference ulcer. Participants were encouraged to use four-layer compression bandaging, unless contraindicated. Lucilia sericata larvae were used with the number guided by manufacturer recommendations. Larvae were left on for three or four days and participants could not receive compression while larvae were in situ. Two different types of larval therapy were used; if more than one application was necessary, the ulcers were redressed with hydrogel while the second application was ordered.

Loose larvae (n=94): provided by Zoobiotic

 

Bagged larvae (n=86): provided by Biomonde

 

Hydrogel (n=87): purilon applied to knitted viscose and applied under compression.

OUTCOMES:

The primary outcome was time to complete healing (assessed from digital photographs by two independent blinded assessors). Secondary outcomes included time to debridement, health-related quality of life, bacterial load, infection with MRSA, adverse events, and ulcer-related pain.

VALIDITY:

Randomisation was stratified by study centre and ulcer area (greater than 5 cm2 or not), then computer-generated with randomly-generated block sizes of three and six. Allocation concealment was by remote central telephone randomisation. There was no loss to follow up. The outcome assessors were independent and blinded. Baseline groups were equal with possible prognostic characteristics adjusted for in the analysis (e.g. high compression). There was no evidence that participants were not treated equally. Overall the methodological quality of the study was high.

RESULTS:

Overall mean age was 74 years and 40 per cent of participants were male. About 75 per cent of participants had ulcers larger than 5cm2 and median duration of ulceration was seven months. Median time to healing was 236 days in larvae group and 245 days in the hydrogel group and not significantly different (table). The groups also did not significantly differ in change in health-related quality of life, presence of MRSA, bacterial load, or adverse events. More ulcer-related pain was reported by the larvae groups and the rate of debridement was greater in the larval therapy groups than in the hydrogel group.

See table below.

 

COMMENTS:

Pragmatic trial that emulated clinical practice comparing new treatment to common established treatment.

Initial analyses compared each larval therapy to effect for overall larval therapy group. Decided a priori that if there was no significant difference between individual and overall larval therapy effects, then results would be reported on combined larval group.

Cost-effectiveness has also been reported for this trial and reported that the therapies likely to produce similar health benefits and costs. Thus no advantage to larval therapy.

Reviewer: Dr Andrew Jull, RN PhD, Associate Professor, University of Auckland & Nurse Advisor – Quality & Safety, Auckland District Health Board.