Expert Pointers On Negative Pressure Wound Therapy
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.