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Applying suction to wounds may speed the formation of granulation tissue, decrease the amount of localized edema, increase blood flow, and accelerate healing. In a prospective study conducted by investigators at the Bowman Gray School of Medicine in Winston-Salem, NC, nearly all of the 300 wounds they treated with a new device called the VAC responded well to treatment. About 75% showed "significant improvement." Results from the study will appear in the next issue of Annals of Plastic Surgery.
The VAC (Vacuum Assisted Closure System, Kinetic Concepts, San Antonio) incorporates a vacuum pump connected by tubing to an open-cell foam dressing in the wound. The pump creates a negative pressure of 125 mm Hg below ambient pressure within and around the sealed dressing. (For information on how one patient responded to the treatment, see the related story, at right.)
The suction deforms cells along the wound margins and induces them to multiply, says Louis C. Argenta, professor and chairman of the Department of Plastic and Reconstructive Surgery at Bowman Gray. In addition, the force of the suction removes fluid from the area immediately adjacent to the wound, enabling blood flow to increase. (For information on complications, see the related story, p. 45.)
The collection of interstitial fluid compromises the microvasculature and lymphatic system, impedes the delivery of oxygen and nutrients as well as the egress of inhibitory factors and toxins.1 Exudate volumes of up to 1000 ml of fluid per day were safely removed from large ulcers without any significant hemodynamic or biochemical imbalances. In addition, decreased bacterial colonization was reported in wounds treated by vacuum-assisted closure compared with those treated conventionally.
"We were looking for a way to treat open wounds and get around the system of just using dressing changes and packing," says Argenta. "A very large number of our patients couldn’t be transferred home or to a nursing home because they required dressing changes that were either too much for family members to handle because they presented insurance problems or because they required specialized nursing care."
Gradually, Argenta and his colleagues conceived of a system that would pull wound margins together with a minimal amount of pain and discomfort, expenditure of nursing time, and long-term care. "Sutures just pull together a couple of cells on the edge of a wound," he says. "We came up with the idea of putting a vacuum in the wound and creating a controlled seal, then using a vacuum applied equally to every cell in that wound to draw them centripedally into the middle of the defect."
At first, he adds, it took a while to convince his colleagues that the technique wasn’t quackery.
Linda Dickerson, RN, BSN, CETN, an ET nurse at Emory University Hospital in Atlanta, knows that the VAC is no fraud. She used it on a paraplegic male patient with five stage 4 pressure ulcers. None had responded well to prior treatment and were even getting larger. "We saw very good results in managing the wounds [with the VAC]. The wounds contracted, blood supply increased, and odor of the drainage decreased," she says. Even though the wounds were large and deep, there was significant granulation." Dickerson kept photographic records of the wounds’ progress.
The VAC was discontinued when muscle/skin flap surgery was ordered, which was only partially successful. "I think if we had continued to to use the VAC to control fluid accumulation after the surgery, the procedure would have been more successful," Dickerson says.
In the Bowman Gray Study, all wounds were treated until they were completely closed, covered with a split thickness skin graft, or until a flap was rotated into the healthy granulating wound bed. The classification of the 300 wounds Argenta and his colleagues treated was as follows:
• 175 chronic wounds those that had been opened and showed no progress toward healing for a minimum of one week. Most had been opened for far longer. These included pressure ulcers, long-term dehisced wounds, venous stasis ulcers, radiation ulcers, and diabetic ulcers. All but four chronic wounds responded well to VAC treatment.
• 94 subacute wounds those that had been open for less than seven days. These wounds responded more rapidly and uniformly than chronic wounds.
• 31 acute contaminated wounds and traumatic injuries, such as gunshot wounds, eviscerations, tissue avulsions and hematomas. Acute soft-tissue wounds developed granulation tissue extremely rapidly and healed more quickly than chronic or subacute wounds. (To see what’s included in the VAC technique, see the related story, p. 46.)
At first, Argenta used continuous suction but subsequently observed better results when suction was applied in cycles of five minutes on and two minutes off. The pulsating effect, he explains, dramatically increases blood flow, which leads to decreased bacterial load in the wounds.
Dressings are changed every 48 hours and can be done at the bedside as a clean, but not necessarily sterile, procedure. Dressings for massive wounds should be done in the operating room or other room equipped for patent sedation. Patients are allowed to shower and bathe during dressing changes and can disconnect themselves from the vacuum pump as desired. Long vacuum tubes permit patients a degree of mobility when connected to the VAC unit. According to Argenta, outpatient nurses and often patients and family members can be trained to change the dressings at home.
Based on his research and clinical observations, Argenta concluded that several interrelated factors are the basis for the success of vacuum-assisted closure:
• the removal of excess interstitial fluid;
• the increase in vascularity and associated decrease of bacterial colonization;
• response of tissues around the wound to mechanical forces.
He also notes that the study revealed 34 independent variables that influence wound healing, highlighting the need for further investigation. A randomized prospective study is planned.
Argenta stresses that vacuum-assisted closure is an adjunctive treatment not meant to replace surgery. In fact, it’s well-suited for patients who are too sick for surgery, and it can be used to take care of surgical complications, such as wound dehiscence. Argenta is trying the system out on burn patients, and he says the military is considering the VAC for treating battlefield wounds.
1. Argenta LC, Morykwas MJ, Vacuum-assisted closure: A new method of wound control and treatment. Annals Plast Surg. In Press.