Technology and product reviews
The observations from this simple in vitro model suggest that the presence of an adhesive layer may be a physical barrier to silver contained within certain dressings. The dressing constructed entirely from gelling fibres with silver distributed homogeneously throughout and without a containing outer sleeve (HF-Ag) exhibited bactericidal activity in this in vitro model. These studies, in conjunction with other published data[5, 18, 19]
suggest that
dressing technology and construction may be important factors in determining the antimicrobial activity of dressings. Clinical
studies and a variety of in vitro models should be used to obtain additional relevant data to assist with product selection.
AUTHOR DETAILS Michael Walker is Senior Research Advisor; Samantha Jones is Microbiology Laboratory Manager; David Parsons is Associate Director; Philip Bowler is Director; Rebecca Booth is Research Scientist, all at Infection, Prevention and Control, ConvaTec Global Development Centre; Christine Cochrane is Research Fellow, Institute of Aging and Chronic Disease, Faculty of Health and Life Sciences, University of Liverpool.
Expert Commentary Jennifer Hurlow is a Nurse Practitioner Wound Specialist
with Plastic Surgery Group of Memphis in Memphis, USA
The evolution of wound care science can be traced back to ancient Egypt and Greece. The Egyptians appear to have developed the understanding that a closed wound heals faster than an open one. As a consequence they invented the adhesive bandage to draw wound edges together. The ancient Greek physician, Hippocrates, found that removal of necrotic wound tissue would lead to a reduction in local inflammation. He used vinegar to cleanse wounds and ointments made of honey or oil, which was then covered with boiled wool[1]
.
Prior to the middle 20th century, wounds were considered to heal better if cleansed with antiseptic before allowing a crust to form. That theory may have been correct as antibiotics were still not widely available until the 1940s. It was thought that infection in wounds depended on bacterial growth, which required warmth, food and moisture. If deprived of any of these elements to a significant degree then bacterial growth would become compromised [2]
. References
1. Forest R. Early History of Wound Treatment. Journal of the Royal Society of Medicine 1982; 1(3) 198–205.
2. Dyas F. Surgical Clinics of Chicago. WB Saunders Company. 1917; 1(2): 447.
3. Winters G. Formation of the
Scab and the Rate of Epithelization of Superficial Wounds in the
Skin of the Young Domestic Pig. Nature1962; 193: 293-4.
4. Dinah F and Adhikari A. Gauze
Packing of open surgical wounds: empirical or evidence-based
practice? Ann Royal Coll Surg Eng 2006; 88(1): 33–36. Available at:
http://www.ncbi.nlm.nih.gov/pmc/ articles/PMC1963638 (accessed September, 2011).
5. European Wound Management Association (EWMA). Position
Document: Wound Bed Preparation in Practice. London: MEP Ltd, 2004.
However, this all changed in 1962 with the landmark preclinical study by George Winter who demonstrated that partial thickness wounds re-epithelialised more rapidly if the surface was kept moist than if crust was allowed to form[3]
. This advancement in understanding triggered the development of
modern wound care dressings. Hydrocolloids first appeared in the 1960s. Foams and alginates were introduced in the 1970s. Hydrogels became available in the 1980s and Hydrofibers emerged in the mid- 1990s[4]
. Unlike gauze dressings, these supported a longer weartime, while maintaining a moist wound
environment and also tended to have lower adherent properties which helped to control pain with dressing changes.
As wound science evolves into the 21st century, the importance of controlling microorganisms has once again become a focus. The emerging and intertwining concepts of critical colonisation, multi-drug resistant bacteria and wound biofilms have brought renewed attention to the importance of wound bed preparation[5]
. This new understanding has led to a proliferation of antibacterial dressings containing
silver. However, the cost effectiveness of these dressings has fallen under scrutiny due to rising healthcare costs and the lack of rigorous clinical data.
The potent antimicrobial action of silver is widely acknowledged and cited in the literature, but clinical evidence demonstrating the superiority and cost-effectiveness of silver-containing wound dressings is limited. In this respect, the interaction of silver with its dressing technology may be important in determining its level of efficacy. For example, if the dressing technology restricts the availability of silver, then antimicrobial activity may be compromised. It is logical to consider that maximising the contact between the antimicrobial component of a dressing and the wound bed is the most cost-effective way to deliver antiseptic action. Maximising the use of silver by delivering the active ion to the wound surface makes economical sense that has heretofore been over looked.
The study by Walker et al (See reference 19 in the accompanying article) examines the performance of different silver dressings in relation to bacterial growth and cell adhesion in the laboratory. In addressing pain, a dressing technology should maintain low adherence thus minimising wound bed trauma and patient discomfort with dressing changes. This in vitro investigation offers further understanding of dressing performance and supports these important clinical considerations.
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