EUROPEAN  TISSUE  REPAIR  SOCIETY

Prof Luc Téot
Service des Brûles, Hôpital Lapeyronie, 371 Avenue du Doyen,
Giraud, 34255 Montpellier, France

Principles

The Vacuum assisted closure system is based on the principle of the use of negative pressure. The VAC is composed of a machine, a tubing connection, a canister, and pieces of foam. Negative pressure was demonstrated to diminish the local amount of germs in a wound and to increase the rate of formation of the granulation tissue. Some other experimental proofs of a direct action of negative pressure on the local biology, mainly the growth factor expression by fibroblasts, are under development. VAC can be considered as a temporary help in transforming a sloughy wound into uniformly granulating tissue, ready to be covered using a standard surgical procedure (skin grafting or flap).

When to apply VAC?

• Large trauma wound: Exposed bones, tendons, vessels, closed joints can effectively be treated using VAC. The germ-free ambience will favour the granulation tissue over these structures. The VAC can be used as soon as the vascularisation of the member has been properly checked as a waiting solution when a rapid coverage cannot be realised. The mean duration of treatment is about two weeks.
• Large sacral ulcers: the contraction effect obtained with the VAC will enhance the spontaneous healing of these difficult wounds. The foam must entirely fill the cavity, in order to prevent any undrained area becoming infected. The mean duration of treatment is about three weeks.
• Post sternotomy disunions: the sternal bone is exposed and generally infected, and a large cavity is open, sometimes exposing the anterior mediastinal area. The VAC is a good tool to treat these badly vascularised wounds after a surgical debridement. The foam must be exactly adapted to the size of the cavity. Complementary pieces of foam can be added, for example to fill an accessory undermined channel. The suction effect will be enough, provided by the main suction foam. The mean duration of treatment is about two weeks.
• Post operative disunions of the abdominal wall; two different situations can be encountered:, depending on the existence of a parietal muscular defect and of the necessity to close the peritoneal cavity using a mesh. In this case, the VAC must be left in place a period of time long enough to obtain a uniform granulation tissue entirely covering the mesh. A skin graft will be proposed as soon as this result will be obtained.

When to stop VAC?

• When a uniform granulating tissue is obtained. Closure of the wound will take a long time. Shortening this process using a simple surgical technique is useful (skin grafting).
• Psychological intolerance.
• Infection.
• No progression of the aspect and the surface of the wound observed on two successive dressings.

Preparing the bed using VAC is necessary in case of a large sloughy cavity wound, difficult to handle. This difficult situation will turn into a simple granulating wound in 80% of the cases.

Dr Jan Mekkes
Dept of Dermatology, Academic Medical Center,
University of Amsterdam, The Netherlands

The goal of wound debridement is to achieve a clean, well vascularised wound bed. Two processes are involved: wound cleaning, more specifically defined as the removal of necrotic tissue, and the induction of granulation tissue formation. Usually these processes occur simultaneously. The shift from yellow or black necrosis to healthy red granulation tissue can be accelerated by surgical excision of a vascular tissue, and by using several local treatments. Some of these wound care materials can be characterised as pure wound cleaners or debriding agents; others just facilitate autolytic debridement by creating a moist wound environment.

Finally, necrotic tissue also disappears because it is replaced by ingrowing new capillaries. It appears to be possible to accelerate the process of angiogenesis by using growth factors such as PDGF (platelet derived growth factor), extracellular matrix components such as hyaluronic acid, and possibly cultured skin grafts.

Dr R Gary Sibbald
Associate Professor and Director of Continuing Education,
Department of Medicine, University of Toronto, Toronto, Canada

The successful use of skin grafts and living skin equivalents (LSE) requires assessment of the underlying cause of treating factors that impair healing. Patient-centred concerns such as pain and quality of life must also be addressed. The optimal preparation of the wound bed requires complete debridement of devitalised tissue, bacterial balance and moisture balance. Skin grafts fail if there is > 1.0 x 10⁶ organisms in the wound bed. Initial clinical application technique for living skin equivalents were extrapolated from split thickness skin grafting. Retrospective analysis of our case series has suggested that an overlap technique may prevent movement of the skin construct and fenestration allows fluid to escape, maintaining cellular contact with the ulcer bed. The stimulation of healing from composite LSE is improved by the presence of the epidermal cell coverage at Day 3 to 7. Chronic wounds that are in superficial and deep bacterial balance at the time of construct application are more likely to show positive healing rates.

The use of biological agents, including LSE, has helped redefine best clinical practices for chronic wound care and stimulate non-healing chronic wounds. Our current first generation products will be gradually replaced with designer LSE that may have extra dermal components or multiple gene copies. LSE with immortalised cells or viral vectors could have the potential to deliver targeted gene therapy to distant body sites.

References:

• Daw G, Browne A, Sibbald G,. Infection in Chronic Wounds: Controversies in Diagnosis and Treatment. Ostomy/Wound Management 1999; 45(8): 23–40.
• Williamson D, Sibbald RG, Skin Substitutes. Wounds November/December 2000. In press.

This Meeting was Sponsored by an Educational Grant from Smith & Nephew.