Given the increasing use of negative pressure wound therapy (NPWT) to spur wound healing, our expert panelists return for the second part of this Q&A discussion on NPWT (see “Inside Insights On Negative Pressure Wound Therapy,” page 24, May issue). They offer specific pearls on the use of NPWT, how to combine the modality with skin grafts and silver dressings, and tips for avoiding wound maceration.
Q: Do you have any pearls for using negative pressure wound therapy (NPWT)?
A: Eric Travis, DPM, utilizes VAC therapy (KCI) mostly at 125 mmHg of continuous suction. For a fragile wound or one with heavy exudation, he lowers the amount of suction. Dr. Travis advises caution with wounds that have significant periwound maceration and necrosis. He notes that he uses VAC open sponge technology to treat tunneling wounds.
To prepare wounds prior to grafting, he applies growth factor technology, namely Regranex (Johnson & Johnson), and Panafil (Healthpoint) with VAC technology. In such cases, Dr. Travis recommends daily dressing changes. He uses silver dressings like Silverlon (Argentum Medical) with VAC therapy as he says they essentially maintain a lower bacterial burden and promote wound healing. Dr. Travis says such a combination is most effective with grafting techniques.
Desmond Bell, DPM, incorporates VAC therapy with compression dressings. He says this is effective in helping prevent accidental disruption of the VAC seal. Compression via an Unna boot can also help reduce inherent edema in the lower extremity and can expedite the removal of exudates, according to Dr. Bell. In addition, Dr. Bell says wrapping a self-adhering bandage around the VAC tubing and subsequently securing it to the self-adhering outer wrap of the Unna boot can help prevent accidental pulling or catching of the tubing.
For Lee Rogers, DPM, the most important pearl is knowing the proper wound in which to use NPWT. As he says, NPWT is best suited for deep, complicated wounds that require granulation tissue formation or enhancement of this tissue. Negative pressure wound therapy is not going to improve a wound that is shallow and granular, asserts Dr. Rogers, as such a wound is already at the desired endpoint. He notes the importance of thoroughly debriding the wound of necrotic and fibrotic tissue prior to using NPWT. Dr. Rogers suggests that one can also use NPWT in difficult locations such as interspaces between toes or around external fixation devices.
Robert Frykberg, DPM, uses NPWT therapy frequently. He includes a TRAC Pad (KCI) on the top of the foot for plantar wounds and also uses NPWT in conjunction with tissue substitutes.
Q: Do you ever combine NPWT with skin graft substitutes? Do you have any special technique? Do you combine negative pressure with silver dressings?
A: Dr. Bell routinely uses VAC therapy in both pre- and post-graft settings. He calls it “an excellent adjunctive modality,” along with surgical debridement, to facilitate wound bed preparation prior to applying the graft.
When using skin substitutes, Dr. Bell secures the graft with steri-strips and then covers the graft with Mepitel. He notes that Mepitel offers a silicone, porous non-stick dressing which will not disrupt the graft. Dr. Bell says Mepitel also provides an interface between the VAC sponge and the graft, which prevents suction of the graft into the sponge. He turns the VAC setting down to 75 mmHg of pressure on a continuous setting, and stops VAC therapy when the amount of exudate in the canister is minimal. Dr. Bell says the primary reasons for skin substitute failure are exudate and bacteria. He says VAC therapy can play an essential role in successfully absorbing the graft into the wound.
Dr. Travis feels VAC therapy is unique and most advantageous to skin grafting in the lower extremity. He has used NPWT with skin grafts, mostly split thickness skin grafts (STSG), and skin graft substitutes like Alloderm or Graft Jacket (Wright Medical) as well as dermal substitutes such as Dermagraft (Advanced BioHealing) and Apligraf (Novartis).
Dr. Travis says his selection of STSG versus allograft is based on the patient as well as the wound’s location, appearance and history. Using VAC therapy with skin grafting techniques appears to potentiate graft healing and adherence, eliminates fluid collection beneath the graft and helps protect the graft site from trauma, all of which commonly cause graft failure, according to Dr. Travis. With VAC therapy and skin grafting techniques, he notes increased conformity between the graft and the recipient site.
Further, Dr. Travis says the foot and ankle present a unique problem with conventional bolster dressings due to the combination of uneven contours with multiple planes of motion. He adds the bolster dressing is essential to secure a graft between two and five days, which is the period of inosculation and capillary ingrowth. However, Dr. Travis says this process can be interrupted on more difficult graft sites where a thin layer of fibrin is the main adherent and exudative fluid from unsecured grafts can ultimately cause graft failure.
Dr. Rogers notes that VAC therapy is very useful as a bolster dressing over a STSG. He uses the VAC until the wound bed is completely prepared and granular. At this point, Dr. Rogers applies a meshed STSG covered with a non-adherent dressing like Adaptic (Johnson & Johnson), Xeroform or Mepitel in order to prevent the graft from adhering to the foam. He uses normal pressure (125 mmHg) for VAC therapy on a continuous cycle and leaves it undisturbed for five days. As Dr. Rogers notes, this maintains the graft in constant, even pressure with the wound bed and prevents hematoma or seroma formation. After five days, Dr. Rogers says one can carefully remove VAC therapy and apply a dressing of choice until the wound heals or, in some cases, requires a second STSG.
Vacuum-assisted closure therapy has increased the rate of graft uptake success for Dr. Travis’ patients. He initially uses sharp debridement or mechanical debridement with the Versajet (Smith & Nephew) to achieve a uniform and granular base, and employs a pulse lavage system to irrigate the wound. He meshes his STSG and acellular allografts to a 1:1.5 ratio and secures them to a final position with 4-0 nylon or staples. Dr. Travis then applies a permeable dressing. He prefers the Silverlon light dressing soaked in mineral oil or Adaptic.
Dr. Travis says one should cut the polyurethane dressing slightly larger to fit the boundary of the recipient site. Then he advises physicians to cut the plastic tubing and place it within the foam dressing. Then the adhesive film accompanying the system should cover the graft site and surrounding skin, according to Dr. Travis. He advocates leaving the VAC dressing on the graft site for seven days with daily clinical inspection. Dr. Travis says if patients are able to tolerate ambulation, one may use a lower leg walking boot due to the tight adherence of the graft to the recipient bed with the VAC dressing. After day seven, he says one should inspect the graft. Dr. Travis continues VAC therapy if he thinks it is necessary. If he sees sufficient graft uptake, he discontinues VAC therapy and replaces it with a moistened Silverlon dressing. Dr. Travis says patients seem to do well with this protocol.
Dr. Frykberg will raise the pressure if necessary when using NPWT with skin grafts. He combines NPWT with silver dressings but not continuously. Dr. Rogers notes that KCI now makes a foam that is impregnated with silver, saying it is only approved for use in acute care settings. Dr. Bell has utilized silver dressings over the Mepitel and between the black sponge for additional control of bacteria in the event that the VAC seal is inadvertently compromised (causing pooling of fluid in the wound).
Q: How do you avoid maceration of the wound edges?
A: Dr. Rogers advises properly cutting the foam so it does not overlap the wound edges, saying it makes a big difference. He also suggests outlining the wound with the VAC drape adhesive to protect the periwound area as he has seen some wound nurses do. In wounds with copious drainage or those in difficult locations, it may not be possible to avoid maceration. In these cases, Dr. Rogers suggests not reapplying VAC therapy for three to four days and perhaps applying Betadine to the wound edges under a wet-to-moist dressing.
To avoid maceration, Dr. Frykberg advises cutting the foam to fit the wound. Sometimes he will use a hydrocolloid border around the wound.
In wounds with heavy exudation, Dr. Travis notes it is difficult to avoid maceration. He notes the importance of getting a good seal with the negative pressure dressing. If the skin around the wound is fragile, he reinforces the area with Duoderm (Convatec), applying it to the area around the wound and applying the adhesive film over that. If hygiene or maceration is an issue, Dr. Travis always increases the frequency of dressing changes with negative pressure therapy.
When wound edges are showing evidence of maceration in between dressing changes, Dr. Travis has used two primary techniques to reverse the problem. After thoroughly drying the surrounding, previously macerated tissue, he either applies stoma paste to protect the tissue before reapplying the VAC drape or applies skin prep and then “window pane” thin hydrocolloid (Duoderm), cut into strips, to the area around the wound.
“Both have yielded excellent results in both outpatient and hospital settings,” notes Dr. Travis.
Dr. Bell is a board certified wound specialist of the American Academy of Wound Management, and a Fellow of the College of Certified Wound Specialists and the American Professional Wound Care Association. Dr. Bell is also the founder and Course Director of the Southeastern Interactive Wound Summit (SIWS), a multidisciplinary annual conference on advanced wound healing.
Dr. Frykberg is the Chief of Podiatry at the Carl T. Hayden VA Medical Center in Phoenix.
Dr. Rogers is the Director of the Amputation Prevention Center at Broadlawns Medical Center in Des Moines, Iowa. He completed a fellowship in diabetic limb preservation and research at the Scholl’s Center for Lower Extremity Ambulatory Research (CLEAR) in Chicago. He has been an investigator for clinical trials involving VAC therapy.
Dr. Travis practices at Beach Podiatry in California. He is on the teaching staff at Fountain Valley Regional Hospital and is involved in the Wound Care Program at La Palma Intercommunity Hospital.
Dr. Karlock (shown at the left) is a Fellow of the American College of Foot and Ankle Surgeons, and practices in Austintown, Ohio. He is the Clinical Instructor of the Western Reserve Podiatric Residency Program in Youngstown, Ohio. Dr. Karlock is a member of the Editorial Advisory Board for WOUNDS, a Compendium of Clinical Research and Practice.
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