Silver dressings increase costs but not healing

1 January 2009

This month’s critically-appraised topic anlyses the value of silver dressing for wound healing

Clinical Bottom Line:

Using silver-donating dressings for treatment of venous leg ulcers in addition to compression does not increase ulcer healing compared to other non-medicated non-adherent dressings used with compression.

Clinical Scenario:

BENPLUS (Best Evidence for Nursing) notifies you of a new trial on silver dressings. You know a recent paper on venous ulcer care showed that silver dressings account for about 60 per cent of dressings used on ulcers in your DHB, but the evidence supporting use is limited. Your interest is piqued.

CLINICAL QUESTION:

In patients with venous leg ulcers, do silver donating wound dressings increase wound healing compared to standard strategies?

Search Strategy:

BENPLUS website: http://plus.mcmaster.ca/np/Default.aspx?Page=1

Citation:

Michaels JA, Campbell B, King B, Plafreyman SJ, Shackley P, Stevenson M. Randomized controlled trial and cost-effectiveness analysis of silver-donating antimicrobial dressings for venous leg ulcers. British Journal of Surgery 2009, 96:1147-56.

Study Summary:

Two arm, parallel group, multicentre, pragmatic randomised controlled trial conducted in specialist leg ulcer clinics in two regions in the United Kingdom (South Yorkshire and Devon). Overall, 304 patients were assessed for eligibility and 213 randomised. Patients had to have had a lower leg ulcer for six or more weeks. Exclusion criteria were: insulin-controlled diabetes, pregnancy, sensitivity or contraindications to silver, ankle brachial pressure less than 0.8, ulcer diameter less than 1 cm, atypical ulcers (including suspicion of malignancy, co-existing skin conditions and vasculitis), or patients receiving oral or parenteral antibiotics.

Patients were treated as per local guidelines for compression in specialist leg ulcer clinics and dressings were changed weekly unless otherwise indicated.

Intervention (n=821):

Silver-donating dressing, choice based on local formulary. Dressings used were Urgotul SSD, Acticoat 7, Aquacel Ag and Contreet Foam.

CONTROL:

Non-adherent dressing, choice based on local formulary. Dressings used were knitted vicose dressings, Urgotul (non-silver version), Biatain, Atrauman and Allevyn.

Outcomes:

Primary outcome measure was proportion healed at 12 weeks (1005 epithelialisation). Other outcomes: proportion healed at six months and one year, time to healing, recurrence rates at six months and one year, health-related quality of life, costs, resource use and cost-effectiveness.

Validity:

Individual patients randomised and randomisation was by computer generated stratified blocks with variable block size. Stratification was on basis of ulcer size and study centre. Allocation concealment was not reported. There was no blinding. Follow up was 98 per cent and analysis on an intention-to-treat basis (although five patients lost to follow up were excluded from analysis). Groups were similar at baseline. Overall the methodological quality of the study was high. 

Results:

There was no difference in healing rates at 12 weeks (table). There was also no significant difference between the groups for healing at six months or one year. Median time to healing was 67 days in the silver-treated group and 58 days in the control group (not significant, p=0.41). There were no significant differences in health-related quality of life and the mean total costs were higher in the silver-treated group than the control group – £417 vs £196 ($933-$440).

Comments:

  • Pragmatic trial, which may dilute effect of silver dressings, but mimics likely effect to be found in real as opposed to highly controlled clinical practice.

     

  • Although different types of silver dressings used, there is no evidence to suggest one type of silver-donating dressing is superior to another and therefore all silver-donating dressings should be treated as one class.
  • No rationale not to generalise findings to New Zealand populations.
  • No adverse events reported
  • Cost-effectiveness analysis reported, but unnecessary as effectiveness not established and therefore silver dressings cannot be dominant economic strategy.

Reviewers:

Dr Andrew Jull, RN PhD, nurse advisor – quality, Auckland District Health Board and associate professor, University of Auckland(School of Nursing).