A Consensus Report on the Use of Vacuum-Assisted Closure in Chronic, Difficult-to-Heal Wounds
The shift toward the practice of evidence-based medicine requires careful review of the literature, coupled with and expert opinion (eminence base) and patient preference.
A review of the evidence base for vacuum-assisted (VAC) therapy (KCI, San Antonio, Tex.) and chronic wounds, performed by interdisciplinary wound care opinion leaders, acknowledged although initial clinical results are promising, a need exists for more random controlled studies to guide clinicians in the integration of VAC therapy for patients with chronic wounds. The gap between the best available scientific evidence (eg, case series and case reports) and every day clinical practice (knowledge translation or research utilization) does not give a balanced view of the appropriate application and duration of therapy clinicians, healthcare systems, and patients need. Often, patients' conditions are complex and do not fit into the evidence base of random controlled trials and controlled studies. To enhance the knowledge base, a consensus group may be formed to obtain expert opinion. However, if a consensus group consists of only individuals who are frequent users of VAC technology, conclusions maybe biased.
In order to compensate for the gap in available literature, as well as in consideration of the bias of dedicated users of VAC therapy, the authors synthesized the evidence base with balanced expert opinion (frequent and occasional VAC therapy users) to develop recommendations for VAC therapy in the treatment of patients with chronic wounds. This consensus should be reviewed in 3 years (2006) or when significant new evidence is published.
General Approach to Chronic Wounds
The first approach to patients with chronic wounds is to identify and treat the cause (see Figure 1). The wound-specific cause must be addressed as well as the patient's health in general. The healthcare provider must ascertain whether physiological and/or pharmacological reasons exist that might interfere with healing.2 An overall assessment of general health and wound-specific factors need to be addressed to determine healability before considering adjunctive therapies.
Adjunctive therapies include electrical stimulation, therapeutic ultrasound, and surgery, as well as using the VAC. A number of published random controlled trials have demonstrated that these therapies are effective.3-6 However, translating some of these treatments into everyday clinical practice (efficiency) may be difficult because of lack of standardized guidelines for use (eg, type of electrode for TENS, voltage frequency, local wound application or application to the periwound skin, frequency and duration of treatments, and type of machinery and modality used), as well as a lack of provider expertise and no access to equipment or reimbursement. Surgical procedures such as grafts and flaps can be combined with adjunctive therapies.
Vacuum-assisted closure is an adjunctive therapy consisting of a non-invasive wound closure system that uses controlled local negative pressure to promote the healing of difficult-to-heal wounds.7 The VAC removes exudate from chronic wounds to help establish fluid balance. Increased exudate in chronic wounds can be caused by low albumin,8 congestive heart failure (right-sided), venous insufficiency, outflow obstruction of a vessel, and infection9 - the cause of which must be corrected just as local fluid must be managed (see Figure 2).
Previous reports on use of the VAC have focused on acute wounds (abdominal wounds, flaps and grafts, postsurgical and traumatic wounds). This article examines the expert opinion, evidence and rationale for the use of VAC therapy in chronic wounds (defined as wound is one that will not heal at an expected rate or length of time10) and translates current knowledge and literature into practical clinical best practices for delayed healing wounds. Previous studies have defined a reasonable time as 4 weeks to predict if progression toward healing is occurring11,12 but systemic and local host factors, size of wound, and location also must be considered when delayed healing occurs (see Figure 1).
Vacuum-Assisted Closure Mechanism of Action and System Components
Vacuum-assisted therapy has been available since 1995, providing subatmospheric pressure through medical grade polyurethane or polyvinyl alcohol foam dressing that is fitted at the bedside to the appropriate size for each wound. The dressing is covered with an adhesive drape to create an airtight seal. An evacuation tube embedded in the foam is connected to a fluid collection canister contained within a portable computer-controlled vacuum machine. This machine creates subatmospheric (negative) pressure at the wound interface surface. The VAC can provide either continuous or intermittent negative pressure and within a range of negative pressure options (-50 mm Hg to -125 mm Hg) to provide optimal fluid level, tissue tension, and capillary flow to enhance vascular profusion.13 Depending on the type of wound, negative pressure initially may be applied in a continuous mode for 48 hours to remove larger amounts of fluids; subsequently, an intermittent mode may be used to provide a more aggressive stimulus for promoting granulation. Negative pressure wound therapy provides a moist wound environment and facilitates removal of slough (liquefied, non-viable tissue) and exudate. Animal and clinical studies suggest that the VAC may decrease bacterial burden.14
A systematic review of the literature on VAC therapy was conducted, which included reports of vacuum-assisted closure in five types of chronic wounds (see Table 1). In general, a wound that is not 30% smaller at Week 4 will not heal by Week 12. Sabolinski and Falanaga19 presented data from the venous Apligraf study. For those chronic wounds not responding to best clinical practices or not demonstrating improvement by reduction in size and are potentially healable (eg, an appropriately treated and debrided pressure ulcer present for greater than 2 months), the VAC can be a useful adjunctive therapy. The goal of therapy may be to decrease the size in these wounds faster than could be achieved in other circumstances.
Consensus Group Guidelines
In 2001, a group of Canadian wound care opinion leaders was assembled through an unrestricted educational grant from KCI Medical Canada Inc. (the manufacturer of the VAC) to define the potential role of VAC therapy in people with chronic wounds. They provided opinions on 13 statements (see Table 2), and a focus group was conducted on a proposed guideline for community care. A document prepared for the Peel Regional Interdisciplinary Wound Care Committee was presented for group comment and modification. The recommendations were summarized and circulated during 2002 for consensus verification.
Methodology. The consensus group of wound care experts was selected by the chair to represent a cross section of Canadian interdisciplinary key opinion leaders. The group included Dr. R. G. Sibbald (Chairperson-Dermatologist, Toronto, Ontario); Dr. J. Baum (Plastic Surgeon, Etobicoke, Ontario); Dr. D. Keast (Family Physician, London, Ontario); Dr. P. Houghton (PhD Physiotherapy, London, Ontario); Dr. J. Mahoney (Plastic Surgeon, Toronto, Ontario); Dr. M. Kliman (Orthopedic Surgeon, Toronto, Ontario); Dr. A. Brassard (Dermatologist, Montreal, Quebec); Dr. M. Paul (General Surgeon, North Bay, Ontario); Karen Campbell (Clinical Nurse Specialist, London, Ontario); Heather Orsted (Clinical Nurse Specialist, Calgary, Alberta); Laura Teague (Clinical Nurse Specialist, Toronto, Ontario); J. Doole (Plastic Surgery Resident, Calgary, Alberta); and Louise Forest-La Lande (Clinical Nurse Specialist, Montreal, Quebec). Dr. L. Argenta (Plastic Surgeon, Winston-Salem, NC) and Dr. M. Morykwas (PhD, Winston-Salem, NC) served as advisors.
The purpose of the consensus group was to define the role of VAC therapy in wound care practice for providers of both acute and chronic wound care. To minimize bias, the experts selected were users and non-users of the VAC in clinical practice. A currently used protocol developed by Peel committee was edited for key concepts. These concepts were formatted into a series of statements for discussion by the expert group. After the discussion, a modified Delphi technique was used to determine consensus. Each individual independently rated the concepts on a five- point Likert scale where 1 = Strongly agree, 2 = Somewhat agree, 3 = Equivocal, 4 = Somewhat disagree, and 5 = Strongly disagree.
The responses were analyzed overall and then divided into users and non-users to detect differences that may relate to issues of clinical application as outlined in Table 2.
Most opinion leaders stated they would use the VAC on chronic wounds with delayed healing. Those already using the VAC also would use this therapy for acute and complex wounds as well as an adjunct to surgery to prepare the wound bed for split-thickness skin grafts or rotational flaps. The panel was divided on using the VAC for salvage in non-healing wounds. The majority of the panel considered intracutaneous fistulae, necrotic tissue, untreated osteomyelitis, and malignancy a contraindication to VAC therapy.
Most experts would apply the VAC immediately after debridement but would sometimes wait 48 hours if bleeding was a concern. They considered 1, 2, 4, or more than 4 weeks to be too long to wait.
The panel preferred using a tissue biopsy as opposed to noting the amount of discharge or bacterial swabs to measure bacterial balance in patients using the VAC. The majority of respondents discontinued the VAC when the wound was closed rather than stopping when exudate could be managed by daily or twice a week dressing changes. No consensus was obtained regarding continuous and intermittent modes of therapy. The preferred pressure for the average patient was 125 mm Hg. Vacuum-assisted therapy users (not non-users) recommended using the VAC with undermining and tunneling, but no consensus was reached as to use in the presence of sinuses. Most clinicians would change the VAC dressing three times a week or if the seal was broken. It was recommended that the canister be changed when it was nearly full. It also was noted that periwound skin protection is best accomplished with hydrocolloid or barrier wipes. Also, the mini-VAC was preferred to facilitate maximum mobility and multiple wounds could be treated, facilitated by the Y connector.
The Delphi responses were incorporated as part of the expert opinion recommendations. These recommendations were circulated to the panel and other key opinion leaders for further comment and modification over a 1-year "revised consensus" period. This document has been incorporated (sometimes with local modifications) into community and institutional wound care best practices protocols in Canada.
Evidence Base for Clinical Use in Chronic Wounds
The consensus group evaluated existing available published case series, but recommended additional research to validate VAC therapy in the treatment of chronic wounds because it is important to compare the VAC to other modern wound adjunctive therapies for difficult-to-heal wounds. The VAC should not be considered the panacea for all wounds - healthcare professionals need to evaluate options for particular patients while continuously monitoring the safe use of the VAC. Distinct goals for care and regular re-assessment time intervals must be determined.
Several case reports and case series (summarized in Table 3) are available in the literature with only two random-controlled trials of patients with pressure ulcers,15,26 but further comparative studies with and without VAC therapy are needed.
Delayed healing (defined as no change in size in 4 weeks) is a challenge in chronic wounds. Because of profuse exudate, such wounds may require daily or more frequent nursing visits in the community. The wound may have to be assessed by a wound care expert; if it were to continue in this fashion, it might take more than 6 months to heal. The committee felt that patients needed to be assessed by a clinician with wound care expertise to be sure each of the components of chronic wound care (treating the cause, patient-centered concerns, local wound care) had been optimized before implementing VAC therapy.
To implement VAC therapy, the wound needs to have been thoroughly debrided, free of active untreated infection (eg, cellulitis), and not involve fistulas to internal organs or body cavities. The possibility of malignant cells being stimulated with VAC therapy was considered to be a contraindication in most cases by most experts in the group. Other contraindications include the patient or caregiver who does not have the ability to understand the treatment or have the ability to adhere to the protocol.
Debridement. In acute wounds, the VAC is often used immediately after debridement. Many members of the consensus panel have observed that adequate debridement of a chronic wound also can stimulate healing.29 Vacuum-assisted therapy can be considered if wound size decreases by less than 30% 4 weeks after major debridement (ie, surgical debridement performed by a surgeon). Otherwise, if appropriate, the VAC may be applied after minor debridement (ie, sharp debridement carried out by a trained healthcare professional at the bedside). The therapy also may be useful with excessive exudate that cannot be managed effectively with daily dressing changes.
The consensus group approach to chronic wounds was different from the approach to acute wounds. Vacuum-assisted therapy may be delayed post-debridement in chronic wounds unless excessive exudate is present that cannot be handled with daily dressing changes. The concern is that it may be prudent to control bleeding for 1 or 2 days after any significant debridement before VAC application.
Continuum of care. When VAC therapy is started in hospital and the patient is discharged to the community, a problem may arise with therapy supervision. Implementing VAC therapy in the community may be delayed due to the additional costs and care delivery logistics in the community and chronic care facilities.20 Failure of VAC therapy in several cases examined may have been due to inadequate staff education and skill, particularly in smaller chronic care facilities. It is crucial to the success of the VAC therapy that adequate procedures are followed.
Enabling the VAC therapy and sponge dressing application procedure can be accomplished in a series of steps (see Table 4). Therapy starts with the selection of black foam sponge for the wound contact layer. If granulation tissue grows into the sponge, the finer pore white sponge is a suitable additional option or a non-adherent dressing interface with the black sponge can be used.
Based on the research, several treatment modifications need consideration when treating chronic wound complications (see Table 5). In the presence of increased bacterial burden, the VAC dressing needs to be changed every 12 to 24 hours. In the presence of anticoagulation, patients may develop areas of bruising indicating the need for both continuous and lower pressure. It is more likely for patients on coumadin to have bruising with normally recommended VAC pressures but a large degree of individual variability and bruising may be seen with aspirin in some patients, necessitating the lowering of the VAC pressure setting. Exposed tendons need to be kept moist and may require non-adherent or other local moisture-retentive dressings. Older patients may not tolerate high pressures due to capillary fragility and discomfort during the therapy. Exuberant granulation or growth of the granulation tissue into the VAC sponge may require the use of a non-adherent interface such as Adaptic™ (Johnson & Johnson Wound Care, New Brunswick, NJ) or Mepitel™ (Molnlycke Health Care, Newtown, Pa.) or a change to the finer white polyvinyl alcohol sponge. Several expert panel members suggested that wound odor may be improved by injecting a povidone iodine solution into the VAC canister.
Several components of wound care and VAC therapy may lead to pain. Sharp debridement before the application of the VAC is often painful. Pressure on wound margins, manipulation of the wound site, and initiation of negative pressure can occasionally be painful. Certain strategies can be implemented (see Table 6), which have modified from Krasner.30 For topical anesthesia, a mixture of two amide local anesthetics called EMLA (Astra-Zeneca, Mississauga, Ontario) can be used. This procedure is not approved by FDA, but is approved in Canada and many other countries. EMLA cream can be applied in a thick coat and covered with an adhesive film for 30 to 60 minutes before debridement. Alternatively, 1% to 4% xylocaine solution or gel has been used topically in some clinical settings. Otherwise, patients can be pre-medicated 30 to 60 minutes before debridement.
Wound margin pressure can be decreased by cutting the VAC. sponge to the size of the ulcer or by using strips of hydrocolloid around the margin. Not cutting the sponge to the size of the wound can be detrimental. Application can be less traumatic by lining the wound bed with either a non-adherent dressing or a small-pore white sponge. Applying saline or lidocaine solution (1% to 4%, with no epinephrine) 15 to 20 minutes before application of the VAC can help with local dressing and VAC application in painful local wound sites.
If VAC pressure is associated with pain, the continuous low-pressure mode should be used from (50 to 75 mm Hg). If the pain persists, the treatment or the cause should be checked and the possibility of infection re-assessed.
Newer VAC Options
A variety of VAC options have been designed to meet the needs of patients and clinicians. The VACATS is an easier to use, more accurate VAC system. It has T.R.A.C. technology - a continuous feedback system that constantly monitors the negative pressure at the wound site, compares it with the target pressure, and adjusts accordingly; thus, enhancing the accuracy and safety of the unit. The VACATS also has a greater internal pump capacity and a large capacity canister with a charcoal filter. The newest version, VACFreedom with T.R.A.C. technology, is designed for use in the community with a smaller, portable system featuring a 300-mL canister.
In addition to the VAC units, new anatomical dressings (eg, a dressing for abdominal compartment syndrome) are currently being introduced in order to make dressing use more efficient.
The results of expert consensus opinion on VAC use for chronic wounds have been developed to provide guidelines for clinical practice and future studies (see Table 7). Many of the lessons learned from acute wounds have been applied to VAC therapy for use in chronic wounds. Treatment modifications for complications have been suggested, along with an approach to the treatment of VAC therapy-associated pain.
Many of the members of the consensus group are now participating in controlled chronic wound studies to examine effectiveness of the VAC therapy. The results of their studies should help further address some of the practical clinical issues to facilitate future investigation of vacuum-assisted closure.