Chronic wounds such as diabetic foot ulcers, venous stasis ulcers and decubitis ulcers are leading causes of morbidity and mortality in elderly patients and significantly contribute to health care costs.1-4 Wounds of these types often lead to complications such as infection and amputation.5-7 The ADA currently reports diabetes is prevalent in at least 17 million Americans, many of whom do not know they have the disease. Of these, approximately 15 percent will experience a foot ulcer or other complication requiring hospitalization during the course of the disease.8, 9
Similarly, venous wounds affect a large population. A recent investigation in Great Britain found the annual prevalence of venous stasis ulcerations to be 1.69 percent in patients ages 65 to 95.4 Regardless of the underlying cause of the ulceration, conservative estimates report that more than 2 million people in the United States are currently being treated for chronic, non-healing wounds.
For many years, chronic wounds have been the subject of intense research in an effort to find methods to increase healing rates and decrease complications. Manipulation of the macroscopic and microscopic environments of wounds has been the key to success in healing both the acute and chronic wound. Wound treatments have ranged from the simple but effective wet-to-dry dressing to topical and systemic pharmacotherapy and biologic agents, including growth factors and skin substitutes or grafts.10
Then there is VAC Therapy (KCI). Well, understanding the usefulness of VAC therapy requires knowledge of the basic science behind a chronic wound. Chronic wounds typically represent a breakdown in the transition between the substrate and proliferative stages of wound healing.12 All stages of wound healing can actually be present in a single chronic wound. Many factors, such as vascular disease, diabetes, pressure, infection, environmental stress, age, nutrition, immune status and pharmacologic agents (both systemic and topical) have been reported to affect the wound environment adversely.13, 14
Using the subatmospheric pressure of VAC therapy can alter the wound environment by reducing bacterial load and chronic, often inflammatory, interstitial wound exudate; potentially increasing vascularity and cytokine expression; and physically contracting wound margins.15 All of these characteristics, particularly the removal of deleterious proteases, may help to convert a tattered wound bed into a red carpet of healthy granulation tissue so it may progress through the subsequent phases of wound healing.16
What The Research Reveals
Since 1995, several studies have looked at the efficacy of the wound VAC in increasing granulation tissue and decreasing mean time to wound closure in various types of chronic wounds.
Morykwas, et. al., performed the initial studies on animals.14 Their technique involved sealing a wound with open-cell foam and suction-tubing inside and applying subatmospheric pressure of 125mmHg below ambient. Using a porcine model, this study found statistically significant increases in granulation tissue production on both the continuous and intermittent settings (63.3 percent and 103 percent respectively). The investigators also found a significant decrease in tissue bacterial counts and a significant increase in random-pattern flap survival.
The podiatric relevance of VAC therapy has been anecdotally reported with promising results. However, only a small number of studies have been performed. McCallon, et. al., presented a small randomized trial.15 Although the study was a pilot study and was underpowered, the time-to-healing difference between VAC treatment vs. saline dressings was somewhat compelling (23 +/- 17 days as compared to 43 +/- 32 days, respectively).
Armstrong, et. al., reported a retrospective analysis at the Southern Arizona Veterans Affairs Medical Center, examining outcomes of subatmospheric pressure in diabetic wounds.17 The purpose of this study was primarily to determine the average duration of VAC therapy in treating diabetic foot wounds as well as the most common complications associated with the therapy. Thirty-one patients with chronic diabetic foot ulcerations (mean pre-therapy wound duration of 25.4 weeks) were treated with VAC therapy after aggressive surgical debridement.
As a result, 90.3 percent of wounds healed without further need for bony resection in a mean time of 8.1 weeks. In their general protocol for the study, they applied the VAC device until granulation tissue completely covered periarticular, tendinous and osseous structures. Researchers used VAC therapy for a mean time of 4.7 +/- 4.2 weeks, with two weeks as the most commonly used regimen.
A Primer On The Basics Of VAC Therapy
Our facility most commonly uses VAC therapy when there is an excessive amount of drainage from venous stasis ulcers and following aggressive, often intraoperative, debridement of diabetic foot ulcers. (See “An Eight Step Approach To Using VAC Therapy” on page 50.)
The VAC device is most commonly used by placing an open cell foam dressing directly onto the wound and covering with a clear occlusive drape to encompass the entire wound. Then you attach the dressing to a vacuum pump, which can provide either continuous or intermittent subatmospheric pressure.
You would order the VAC and associated supplies from KCI. The foam dressing comes in two varieties. The first is a black sponge or polyurethane foam, which is recommended for stimulating granulation tissue and wound contraction. The white sponge, or poly-vinyl-alcohol soft foam, is a denser sponge with smaller pores. This sponge is recommended for growth of granulation tissue into the foam needs to be prevented or when the patient cannot tolerate the black sponge due to pain. You can order both of these sponges in small, medium and large sizes.
Until very recently, there were two types of vacuum pumps available, a VAC and mini-VAC. The mini-VAC is seldom used in podiatry at this time because the canister that holds the drainage is too small. The intermediate VAC (which will be available in the near future) may have potential for wide usage in podiatry due to its smaller size and a canister that is large enough to hold the amount of drainage from venous stasis ulcers and diabetic foot wounds. This intermediate VAC may also allow more outpatient therapy as it will be easier to carry around. Furthermore, another model called the new VACATS (Advanced Therapy System) has an on-screen user’s manual and sophisticated controls for speed and force of suction.
How To Get Maximum Results From VAC Therapy
Once the VAC arrives, you should aggressively debride the wound to decrease the amount of fibrotic and nonviable tissue. Clean the wound and completely dry the surrounding tissue. Take a tracing of the wound to facilitate the ease of cutting the sponge to the size of the wound at the present and subsequent dressing changes. You should cut the sponge to be slightly smaller than the wound. Either leave the suction tubing in the sponge or remove and reinsert it into the sponge at the end of the application of the dressing. At our facility, we tend to remove the tubing prior to applying the dressing.
Then place the sponge onto the wound and loosely cover the wound with the clear occlusive drape. Placing the drape loosely will allow the suction to create a tight seal along the perimeter of the wound and decrease periwound maceration.
At this time, you may make a slit in the drape and sponge to allow insertion of the tubing. Then cover the tubing with an additional piece of drape or OpSite (Smith & Nephew), making sure to pinch the drape around the tubing to create a complete seal. Proceed to connect the tubing to the vacuum pump. The most common pressure setting is 250mmHg, which you can set at either continuous or intermittent. If the vacuum does not seal, check for leaks. The leaks most commonly occur around the tubing or at the perimeter of the drape. Squeezing the drape will often create the necessary seal. You may need to apply additional layers of the drape to create a seal. (Much of this step may soon be eliminated with new occlusive dressing/sponge combinations available from the manufacturer.)
Generally, you would change the VAC every 24 hours for infected wounds and 48 hours for non-infected wounds. During the dressing change, debride, lavage and clean the wound as you would normally do in your institution.This will decrease the bacterial burden and decrease the typical odor omitted from this wound care method.
When using a modality such as the VAC, you must also consider when to discontinue its use. This is very important, especially when considering the cost of the VAC pump. For the venous ulcers, we will typically use the VAC until the wound is almost completely closed. When treating diabetic foot wounds, we generally use the VAC to cover osseous and tendon structures, and achieve a healthy, granular bed. Once this occurs, you must evaluate the wound at each dressing change. If the VAC is not making a significant improvement in the wound size or depth, then discontinue using the VAC and reconsider your patient for concomitant morbid conditions such as occult infection or untreated ischemia.
A Few Thoughts On Modifications And Reducing Complications
While the aforementioned technique for applying the VAC described the typical application, you may need to make minor modifications to the procedure.
For example, consider the following case study. A 65-year-old male presents with two ulcerations on the R/L foot that have been present for several months. Due to the locality of the wounds and the need to use a vacuum over both wounds, we decided to use the quick connect Y-connector supplied by KCI.
We cut a piece of the black sponge into two pieces to fit the size of each ulcer and then placed the drape loosely onto the patient. Then we placed a slit into the drape and put a sponge over each ulcer. We then placed the tubing into the sponge and covered it with a small piece of the drape. We proceeded to connect each piece of tubing to the vacuum pump via a quick connect Y-connector. This modification allows you treat multiple ulcers at the same time.
The main purpose of the aforementioned study at our institution was to identify the most common complications associated with VAC use. In this study, peri-wound maceration (at a 19.6 percent prevalence) was far and away the most common complication.16 We have found that, in the case of extensive maceration, there are occasions when you need to discontinue the VAC for one to two days. This VAC “holiday” will allow the periwound tissues to recover or allow you to attempt to reduce the bacterial burden, thus facilitating wound healing. However, during the “holiday,” the wound might continue to drain as if the VAC were connected. Therefore, you should use an absorptive dressing to prevent maceration.
In order to decrease this need for VAC “holidays,” our institution has begun to apply the hydrofiber dressing Aquacel (ConvaTec) to the perimeter of the ulcer. This technique has greatly decreased the severity of periwound maceration to much lower levels. We and practitioners at other institutions have used a variety of skin preparations and barrier creams with some success as well.
There are several benefits to using VAC therapy. A primary benefit is the often very impressive creation of rapid granulation tissue over osseous and tendon structures. When treating venous and diabetic foot ulcers, this modality is beneficial for its ability to increase local vascularity and decrease chronic inflammatory exudates and non-viable tissue. We and other investigators have noticed a rapid healing rate in treating both venous ulcers and diabetic foot wounds. We look forward to both our participation in and results from randomized controlled trials in this area that should help either to confirm or refute these observations.
Dr. Armstrong is the Director of Research and Education within the Department of Surgery, Podiatry Section at the Southern Arizona Veterans Affairs Medical Center in Tuscon, Ariz.
Dr. Short is a second-year resident at the aforementioned institution. Dr. Claxton is a third-year resident at the aforementioned institution.
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