SILVER DRESSINGS DOES THEIR EFFECT ON MICROBES JUSTIFY THE EXPLOSION IN THEIR USE - PowerPoint PPT Presentation

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SILVER DRESSINGS DOES THEIR EFFECT ON MICROBES JUSTIFY THE EXPLOSION IN THEIR USE

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Precious & heavy metals have attracted health interest through the ages ... the other, necrosis, causes inflammation and tissue damage. HUMAN STUDIES ... – PowerPoint PPT presentation

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Title: SILVER DRESSINGS DOES THEIR EFFECT ON MICROBES JUSTIFY THE EXPLOSION IN THEIR USE


1
SILVER DRESSINGSDOES THEIR EFFECT ON MICROBES
JUSTIFY THE EXPLOSION IN THEIR USE?
  • OCTOBER 2005 ADELAIDE
  • ASSOCIATE PROFESSOR
  • MICHAEL WOODWARD
  • AUSTIN HEALTH

2
HISTORY OF SILVER
  • Precious heavy metals have attracted health
    interest through the ages
  • Silver coins used to purify water in middle ages
  • Silver in many salves and ointments
  • Silver nitrate recognised as antiseptic in 19th
    century
  • SSDC first used in 1968
  • Allowed more extensive use than silver nitrate
  • Less skin discolouration
  • Revolutionised burns management

3
WEAKNESSES OF SSDC
  • Ag rapidly binds to tissue Cl- , creating AgCl
    ,which is inactive

  • So need to apply large quantities,and frequently
  • Pseudo-eschar formed
  • Binds tightly to wound surface
  • Removal necessary but painful
  • Can macerate wound

4
NEW SILVER PRODUCTS
  • Prolong the release of ionic silver
  • Or absorb wound fluid into silver-impregnated
    product
  • Utilize modern wound management principles
  • Most based on existing modern products,with
    silver added

5
SILVER DRESSINGS AVAILABLE IN AUSTRALIA
6
HOW DOES SILVER ENHANCE WOUND HEALING?
  • Controls microbial burden
  • Other effects
  • Controls inflammation
  • Alters proteases
  • Promotes apoptosis

7
EFFECTS OF MICROBES ON WOUND HEALING
  • 1. Contaminate all wounds
  • 2. Critical colonisation
  • Delays healing
  • May lead to
  • 3. Infection

8
MICROBES WOUND HEALING
  • Contamination may be helpful to wound healing
  • Promotes beneficial inflammation
  • Increases blood flow
  • Critical clonisation/infection delays healing
  • Bacterial endotoxins elevate cytokines (eg IL-1
    and TNF),causing increased proteases and reduced
    growth factors
  • Vessels occluded
  • Bacteria spread to and damage adjacent healthy
    tissue

9
BIOFILMS
  • Microbes on wound surfaces usually form a biofilm
  • Complex community embedded in a polysaccharide
    matrix
  • Resembles a single organism
  • Excretes via channels,attracts and shares
    nutrients,resists external threats
  • Bacteria within can reduce metabolism
    (hibernate)

10
BIOFILMS
  • Bacteria in a biofilm up to 1000 times more
    resistant to antibiotics
  • Protected by the matrix
  • Reduced metabolism
  • So factors which aim to control bacterial burden
    must work on biofilms

11
CONTROLLING MICROBIAL BURDEN
  • ANTIBIOTICS
  • May be effective for infection
  • But increasing resistance
  • In critical colonisation, often ineffective
  • Biofilm resistance
  • Multiple organisms
  • Too late
  • In surgery, giving Ab after operation increases
    infection rate

12
CONTROLLING MICROBIAL BURDEN
  • ANTISEPTICS
  • Much less resistance
  • as short acting and locally acting
  • Penetrate and control biofilms
  • COMMONLY USED ONES
  • Chlorhexidine
  • Alcohol
  • Iodine
  • Silver

13
EFFECTS OF SILVER ON MICROBES
  • Attracted to the proteoglycans in cell walls
  • mammalian cells lack these
  • Denatures microbial proteins
  • esp. those involved in respiration
  • Also affects microbial DNA

14
RESISTANCE TO SILVER
  • Extremely rare
  • One mechanism microbes develop ability to pump
    silver out
  • Not seen in bacteria resistant to multiple
    antibiotics
  • Not shown to spread between patients

15
EVIDENCE FOR EFFICACY OF SILVER PRODUCTS
  • 1. In Vitro
  • 2. Animal Models
  • 3. Human Studies

16
IN VITRO STUDIES
  • Bowler et al
  • Foetal calf serum
  • Inoculated with various organisms
  • - At 0,4 and 9 days
  • Small piece of Aquacel Ag or control hydrofiber
    added
  • Cultured for persistent organisms

Bowler PG et al.J Burn Care Rehab 2004,25192-60
17
BOWLER ET AL - RESULTS
  • Single piece of Aquacel Ag nearly completely
    eliminated microbes up to 9 days later
  • Despite reinoculations
  • Effective against
  • Pseudomonas
  • MRSA
  • VRE
  • anaerobes
  • fungi/yeasts

18
IN VITRO STUDIES
  • Wright et al
  • Inoculated organisms onto dressings coated with 3
    different silver forms
  • Nanocrystalline
  • SSDC
  • Silver nitrate
  • then extracted surviving organisms 30 minutes
    later
  • Results
  • Nanocrystalline silver most effective
  • SSDC partly effective

Wright BJ et al.Am J Infect Control 199826572-7
19
IN VITRO STUDIES
20
IN VITRO COMPARATIVE STUDIES
  • Recent study compared antimicrobial effect of 4
    products
  • Acticoat most rapid
  • Contreet slower but effective against same broad
    range of bacteria
  • Actisorb only effective within product(not at
    wound surface)
  • Avance not effective

Thomas et al J Wound Care 200312101-7
21
ANIMAL STUDIES
  • Porcine contaminated wound model
  • wounds created in young pigs
  • contaminated with Ab-resistant bacteria
  • then dressed
  • then cultured and biopsied

Wright et al. Wound Repair Regeneration
200210141-9
22
PORCINE MODEL - RESULTS
  • Nanocrystalline silver dressing improved healing
  • Better quality granulation tissue on inspection
  • Better graft uptake
  • 6/6
  • compared to 0/6 control wounds
  • Reduced metalloproteinases on Bx in
    silver-treated wounds
  • Increased apoptosis after silver Rx
  • healthy cell death
  • the other, necrosis, causes inflammation and
    tissue damage

23
HUMAN STUDIES
  • No gold standard study with silver
  • Nearest is probably CONTOP
  • Naturalistic comparator trial
  • Partly randomised
  • Silver or standard care which could be silver
  • 1,000 patients to be enrolled
  • Findings on first 352 presented at WUWHS meeting,
    Paris July 2004

24
CONTOP
25
CONTOP
26
P0.006
27
CONTOP
28
CONTOP
  • Results on 619 patients at Silver Symposium in
    Perth, September 2005
  • 50 reduction in size at week 4 with Contreet
  • 34 with standard care

29
INTERPRETING CONTOP
  • Not published
  • Not fully randomised
  • No rater blinding
  • Outcomes clunky
  • P values hard to understand
  • Results apply only to this silver product
  • and presumably sponsored by manufacturer
  • but most drug research is

30
CONTREET FOAM vs ALLEVYN
  • 109 patients with chronic venous leg ulcer or
    mixed arterial/venous ulcer
  • 13 Centres
  • Healing stalled
  • Less than 30 reduction in size at 4 weeks
  • Features of critical colonisation
  • Pain, appearance

31
CONTREET FOAM vs ALLEVYN
  • RESULTS
  • CONTREET
  • 45 reduction in size by 4 weeks
  • ALLEVYN
  • 25 reduction in size by 4 weeks
  • OTHER SECONDARY ENDPOINTS IMPROVED WITH CONTREET
  • less exudate
  • less leakage

32
RDNS/SILVER CIRCLE STUDY
  • Planned 360 patients with wounds not decreasing
    in size or signs of critical colonisation
  • Randomise to cadexomer iodine or silver product
    (Iodosorb or Acticoat)
  • Follow-up 3 months 2-weekly reviews
  • Endpoints wound size, use of antibiotics,
  • adherence, wound swabs,
  • nurse and client satisfaction
  • Results 2007

33
CHRONIC VENOUS ULCERS
  • 25 patients with chronic venous ulcers
  • Contreet foam use led to 56 reduction in ulcer
    area over 4 weeks
  • IMPORTANT-not selected for colonization
  • No comparator group

Karlsmark et al J Wound Care 200312351-4
34
CHRONIC WOUNDS
  • Randomised non-blinded study in chronic wounds
    with no clinical infection, using an activated
    charcoal silver dressing
  • Reduced bacterial levels in 85.1 of 67
    silver-treated wounds by day 15
  • Compared with 62.1 of 58 control wounds
  • Healing times not reported

Soriano et al J Wound Care 200413421-3
35
SIGNIFICANCE OF THESE LAST 2 STUDIES
  • These suggest a role for silver even when
    microbial burden not an obvious factor
  • Not clear if this influenced dressing selection
    in CONTOP
  • probably did
  • However, role of silver may still be via control
    of microbes, as last study suggests

36
BURNS STUDIES
  • 1. Open-label non-comparator study with Urgotul
    SSD
  • Low rate of Staph aureus colonisation
  • 1 of 41 subjects
  • 2. Another non-comparative trial with Aquacel-Ag
  • 17 patients
  • healed in average 14 days
  • only one required grafting

1.Carsin et al J Wound Care 200413145-8 2.Caruso
et al J Burn Care Rehab 20042589-97
37
DIABETIC FOOT ULCERS
  • Non-randomised trial of diabetic foot ulcers
    treated with Contreet in 27 patients
  • small comparator group of 6 ulcers in same
    patients not treated with Contreet
  • average healing 56 over 4 weeks
  • not reported in comparators
  • two treated ulcers infected,compared to all 6
    comparators

Rayman RG et al British J Nursing 200514109-14
38
IS THIS EVIDENCE SUFFICIENT?
  • By comparison to other areas of health practice
  • POSSIBLY
  • By comparison to pharmaceutical research
  • DEFINITELY NOT

39
COST EFFECTIVENESS DATA
  • ALWAYS SEEMS TO JUSTIFY EXPENSIVE PRODUCT USE
  • Use a commonsense approach
  • And ask - can service or patient afford it,
    even if cost effectiveness claimed

40
HOW SHOULD THIS EVIDENCE INFLUENCE CLINICAL
PRACTICE?
  • Consider silver dressings for critically
    colonised wounds
  • and return to standard dressing once microbial
    burden controlled
  • Try a different silver product if initial one
    fails
  • But no human head-to-head trials and such trials
    notoriously unhelpful
  • always seem to favour sponsors product !

41
EVIDENCE-BASED USE OF SILVER
  • Consider silver product in non-healing and slowly
    healing wounds
  • even if no evidence of microbial critical
    colonisation/infection
  • could biopsy first to establish such burden, but
    evidence only exists for value of high counts
    revealing infection, not lower counts and
    colonisation
  • and silver may be effective even with no
    microbial burden

42
EVIDENCE-BASED USE OF SILVER
  • Infected wounds need
  • Antibiotic
  • Debridement
  • Silver may add extra benefit
  • But no human studies
  • Only support from in-vitro and porcine studies

43
EVIDENCE-BASED USE OF SILVER
  • Always return to first principles
  • Fully and repeatedly assess
  • Compress if venous
  • Ensure adequate blood supply
  • Reduce pressure
  • Improve nutrition
  • Treat co-morbidities
  • Assess social circumstances
  • Silver is not a panacea

44
THE FUTURE
  • A Challenge
  • Design and participate in well-designed and
    powerful trials
  • Avoid the temptation of easy research only
  • More case series
  • No comparator group
  • Until then, use silver mainly for control of
    microbial burden
  • This is where the evidence is currently strongest
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