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he purpose of these guidelines is to summarize the consensus of a multidisciplinary expert advisory panel convened to determine appropriate use of negative pressure wound therapy (NPWT), also known as Vacuum-Assisted Closure® or V.A.C.® Therapy (Kinetic Concepts, Inc., San Antonio, Texas), in the treatment of diabetic foot wounds. The Tucson Expert Consensus Conference (TECC) on V.A.C. Therapy was convened in an effort to guide the direction for future research either to confirm or refute current consensus while providing practical guidance to the clinician currently treating diabetic foot wounds. In part two of this series, we review the indications and benefits of NPWT, list the contraindications of NPWT, and provide questions and answers regarding the appropriate use of NPWT.

       In 1997, Argenta and Morykwas conducted studies on NPWT and showed that there was enhanced granulation tissue formation and improved bacterial clearance when compared with control dressings.¹ There also appeared to be increased flap survival. Some of the therapeutic benefits of NPWT that were postulated by Morykwas² as well as Argenta and Morykwas in 1997³ included aggressive reduction in local or interstitial edema, increases in local blood flow, evacuation of excessive drainage, decreased bacterial colonization, and converting an open wound to a controlled closed wound, which allows less frequent dressing changes and protects the wound from the patient and his or her surroundings. Therapeutic benefits also included providing a moist wound healing environment, which has become the standard of therapy.
       Indications. The V.A.C.® system is cleared by the US Food and Drug Administration (FDA) for promotion of healing in wound types including pressure ulcers, other types of chronic wounds, acute and traumatic wounds, in conjunction with meshed grafts and flaps, and partial-thickness burns. This therapy is adjunctive for managing large defects and heavily draining wounds because of its ability to control exudate from unhealthy wounds after debridement. As shown in several studies, NPWT can prepare wound beds for grafting or for delayed primary closure very effectively and is also useful for those patients who are not suitable surgical candidates.^3,4 See sidebar on page 26 for a list of contraindications and precautions on the use of NPWT.

       Benefits. Improvement of graft take. In many clinical applications, NPWT will be used not to affect primary closure but to enhance the progression of wounds in preparation for early surgery. The modality can also stabilize flaps, grafts, and traumatic wounds in preparation for eventual closure. Initially, some clinicians feared that suction from NPWT might disturb a graft from its recipient bed, but the negative pressure actually compresses and enhances the take of the skin graft. Another benefit of NPWT in this situation is to prevent fluid accumulation underneath the graft. In a study by Schneider, et al.,⁵ investigators used a nonadherent porous dressing between the graft and the dressing for skin grafts. This created an interface between the graft and the dressing that applied continuous pressure to the graft against the recipient bed. The investigators left the dressing in place for three or four days until the graft had taken.
       Wound bed granulation. In conjunction with the basic tenets of wound healing and appropriate wound care (including debridement), NPWT can stimulate angiogenesis.^6–9 By applying negative pressure uniformly to all points of a wound, NPWT will assist in wound contraction and the development of new tissue, not just in the diabetic foot but for patients who are nonoperative (e.g., those who are too sick to go to the operating room for closure). Although use over bone, tendon, or hardware was an early contraindication to NPWT there are now reports in the literature that support its use with exposed deep structures.^3,10 NPWT in these wounds may enhance angiogenesis and granulation tissue formation to the point that they may be successfully grafted or closed. Some clinicians will apply NPWT in the operating room; however, it is necessary to wait until hemostasis is achieved along with adequate drainage and resolution of acute infection before applying this therapy.
       Ease of dressing changes. An additional benefit is the ease of applying these dressings. NPWT allows reduced hands-on care, meaning the dressing changes can be performed every 48 hours rather than every 12 hours unless infected (12–24 hours for infected wounds). The device can be applied at home or in alternative care settings. It can be changed more frequently if there is concern about what is taking place under the dressing in the early stages. More than one wound can be treated at a single time by using connecting foam bridges or Y connectors. A minimum of 22 hours a day of active therapy is important since these dressings should not be left on a wound without the therapy being active (either continuous or intermittent).
       As adjunctive therapy. NPWT is most often used adjunctively with other agents or modalities. A brief review by Espensen, et al.,¹¹ described multimodal therapy using a tissue substitute in concert with NPWT. Increasingly common is the use of NPWT as a means to promote take of these skin substitutes. Usually there is some type of nonadherent dressing applied between the graft and NPWT dressing.

Important Questions and Answers on the Appropriate Use of NPWT

1. How long should NPWT be used in treatment of a diabetic foot wound?
       In most cases, NPWT may be used to achieve a healthy granular bed after which other modalities or surgical procedures may be considered. There may be instances when NPWT can be used to complete closure/healing by secondary intention (e.g., when a patient is too sick to undergo additional procedures or the patient refuses additional surgical intervention).
2. Should NPWT be applied to a wound that has not been debrided?
       No. A neuropathic diabetic foot wound must be adequately debrided and pressure offloaded in order for NPWT or any other wound healing modality to be effective in the diabetic foot. While an initial debridement prior to application of NPWT is mandatory, debridement prior to each subsequent application of NPWT is not always indicated. The clinician should be guided by wound appearance and the presence of non-viable tissue.
3. How should the patient using NPWT be evaluated on an outpatient basis?
       Regular evaluation by the responsible clinician should be performed to evaluate for wound progress. Failure of improvement in the wound over a 2- to 4-week period should signal the requirement for reevaluation of the current NPWT, including the potential for occult ischemia, inadequate debridement, inadequate pressure offloading, or presence of infection.
4. When should NPWT be applied following lower-extremity bypass?
       While there are few data to guide a clinician in this area, NPWT may be applied to a wound distal to a bypass graft following a revascularization procedure provided there is no evidence of residual infection, active bleeding, or necrotic tissue. When dealing with the presence of an exposed vascular graft, preferred alternatives are to reroute the graft or to use local flap or coverage techniques. If these are not applicable then NPWT could be applied cautiously and under the close supervision of the attending surgeon.
5. When should NPWT be applied after incision and drainage of infection?
       It is the opinion of this committee that NPWT should not be applied immediately after an incision and drainage procedure. The wound generally should be evaluated for a positive response for at least 24 hours prior to application of NPWT. In the instances when immediate application is employed, the wound should be evaluated frequently (every 12 hours) for the first 2 to 3 days.
6. How should NPWT be used in patients with osteomyelitis?
       NPWT is not a treatment for osteomyelitis. Osteomyelitis in the diabetic foot may be surgically resected or suppressed medically. These options should be used before or concomitant with NPWT. It is useful to obtain granulation and coverage after medical or surgical treatment of osteomyelitis in the foot. In these situations, the use of NPWT is favorable.
7. How should nonadherence (i.e., noncompliance) be defined in the patient on NPWT? When should NPWT be discontinued in this population?
       Nonadherence with NPWT is defined as a failure of the patient to follow the advice given when provided with the instrument. Patients who historically demonstrate their inability or unwillingness to participate in their own care generally should not be treated with NPWT. As with many wound care modalities, NPWT is an expensive device and should be reserved for patients who are likely to adhere to the guidelines to its use. Adequate adherence to care means the patient is using the device appropriately 24 hours a day and receiving changes every 48 hours or 12 to 24 hours if the wound is infected. Choosing the appropriate NPWT device for the appropriate patient may improve adherence; however, ultimately adherence to care is the patient’s responsibility. Repeated events of nonadherence to this modality are grounds for choosing an alternate technology or approach to wound care.
8. How should NPWT be used in combination with other modalities?
       There are few data to guide the clinician in the choice for combination wound therapy. However, many clinicians choose to augment NPWT with other adjunctive agents. The members of the TECC and other investigators have had experience with “combination therapy,” which includes but is not limited to NPWT’s use with bioengineered skin, silver dressings, other various antimicrobial agents, and cytokine therapy. Furthermore, there is emerging evidence that NPWT may improve survival of split-thickness skin grafts.
9. Should small, superficial, noninfected wounds be considered for NPWT?
       Patients that clinically may be at higher risk for failure to heal, such as patients with wounds that are larger, deeper, and have prolonged courses of previous therapy or a long duration, are more likely to be candidates for primary NPWT use. Smaller superficial wounds without infection or ischemia, if responding well to adequate debridement and offloading, generally are not candidates for primary use of NPWT. In general, the superficial, noninfected, nonischemic wound that is progressing well with adequate debriding and offloading does not require NPWT.
10. How should we define success in future studies of NPWT?
       Randomized, controlled trials on NPWT need to be done with primary and secondary endpoints. While a primary endpoint to any randomized controlled trial should be time to complete epithelization or prevalence of healing at that time point between the two groups, the other endpoints may be valuable in guiding potential benefits of NPWT. Secondary endpoints may include the following: rate of healing, time to a complete wound bed preparation/healthy granular bed, requirement for further procedures, quality of life, pain reduction, cost of care, the level of nursing care required, rate of healing, proportion of peritherapeutic complications, and proportion of amputation at given time points. Ideally the evaluations of active and control groups should be evaluated by observers blinded to therapy.

       To order a copy of the supplement titled “Guidelines regarding negative pressure wound therapy in the diabetic foot: Results from the Tucson Expert Consensus Conference (TECC) on V.A.C.® therapy,” call 800-237-7285, extension 246.