Introduction
Surgical wounds left open to heal by secondary intention have an increased risk of infection because of the lack of an epidermal barrier.1 Surgical site infections are associated with increased lengths of hospital stay, higher costs, readmissions, and patient morbidity.2,3 New technologies and methods of treating acute and chronic wounds are emerging.4 Two recent developments are noncontact low-frequency ultrasound (NCLFU) and negative pressure wound therapy (NPWT) on open wounds. Since the outcomes of using NPWT combined with NCLFU on open abdominal surgical wounds have not been widely documented in the literature, we elected to present a series of 4 patients who had open abdominal surgical wounds and were treated with NPWT combined with NCLFU.
Case History
Following approval by the Mayo Clinic Institutional Review Board, a retrospective analysis of the 4 cases was performed to evaluate wound tissue appearance, wound dimensions, and characteristics of the surgical wound bed. Photographs were used to track wound healing progression.
Four hospitalized patients who underwent colorectal surgery that resulted in open abdominal wounds were treated using NCLFU (MIST Therapy; Celleration Inc, Eden Prairie, Minnesota) in combination with NPWT (V.A.C.; Kinetic Concepts, Inc, San Antonio, Texas). The NCLFU therapy was performed 3 times a week. Sessions were coordinated with the timing of the NPWT dressing change. Selective sharp wound debridement with a dermal curette was performed as needed during the dressing change, to remove loosened, devitalized tissue. One patient required surgical debridement of necrotic tissue (case 3). No clinically relevant adverse effects from either intervention were noted during the observation period.
Case 1
A 55-year-old woman was admitted with abdominal pain that led to a cholecystectomy completed on hospital day 1. Her complex past medical history included multiple sclerosis and depression. She also has a history of ulcerative colitis requiring a colostomy with ileostomy and Kock pouch procedure at the age of 21 years, and revision of the ileostomy at the age of 31 years. She has been diagnosed with peptic ulcer disease, pneumonia, superior mesenteric artery syndrome, and deep venous thrombosis, resulting in Greenfield filter placed at the age of 39 years. Pernicious anemia was treated with vitamin B12 injections. On hospital day 2, a sigmoidoscopy was needed because of retained pills and feculent material found in the Kock pouch. The procedure was complicated by a bowel perforation, and the patient was returned emergently to the operating room (OR) for a takedown of her Kock pouch and end ileostomy. After the operation, the abdomen remained open at the surgical site.
On hospital day 3, the patient returned to the OR for an abdominal washout, placement of a mesh graft (XenMatrix; Davol Inc, Warwick, Rhode Island), and initiation of NPWT. After this procedure, she went to the intensive care unit with norepinephrine infusion to treat hypotension. On hospital day 7, she was transferred to the general care floor, where she was consuming a general diet with additional liquid nutritional supplements. The NCLFU therapy was added 3 days per week to further assist with cellular stimulation and wound debridement until her dismissal on hospital day 27. On hospital day 13, the wound edges were beefy red with 1 necrotic area at the 6 o'clock position (Figure 1A and Table 1). The wound measured 21 cm long by 6 cm wide with a depth of 0.5 cm. On hospital day 22, the wound continued to be beefy red around the edges but with no evidence of necrotic tissue (Figure 1B and Table 1). After 18 days of combined therapy, the wound measured 20 cm long by 6 cm wide and had a depth of 0.2 cm. The wound edges were pink with increased granulation tissue formation and evidence of granulation budding within the mesh graft. After 20 days of combined therapy, the wound area had decreased approximately 5% and the volume decreased 62%. The patient was dismissed to a local long-term care facility with continuation of NPWT; all follow-up was completed by the local primary care provider, and therefore long-term wound closure data are not available.
Case 2
A 48-year-old woman with a history of incisional and parastomal hernia was admitted for surgical repair of her symptomatic parastomal hernia. The newly constructed stoma became ischemic and required a return to the OR on postoperative day 9. After this second procedure, the patient became hypotensive, tachycardic, and tachypneic, with increased oxygen requirements and elevated white blood cell counts. Abdominal computed tomographic scan showed extravasation of oral contrast medium with fluid collections around the liver and free air in the abdomen. The patient returned to the OR on hospital day 10 for an exploration procedure, abdominal washout, drain placement, wound debridement, placement of biologic mesh, and NPWT. On hospital day 18, NCLFU therapy was initiated to enhance the proliferative phase of wound healing and assist with bioburden control. The wound edges presented with minimal signs of granulation tissue (Figure 2A and Table 1) and measured 8.5 cm long by 11 cm wide by 1 cm deep. Eschar was present on the left wound edge. After 5 days of combined therapy, the measurements were nearly the same; however, the amount of granulation tissue at the edges of the wound bed increased and visible granulation tissue was forming within the biologic mesh (Figure 2B and Table 1). The eschar along the left edge decreased secondary to autolytic debridement as a result of NPWT and NCLFU. The patient was dismissed on hospital day 24 to continue NPWT followed by her local primary care provider.
Case 3
A 33-year-old woman with a history of ulcerative colitis was admitted with abdominal pain, fever, 30-lb weight loss, and bloody stools. On hospital day 6, the patient underwent an open subtotal colectomy. On hospital day 13, she returned to the OR due to feculent peritonitis and because her wound failed to show signs of granulation postoperatively. On hospital day 15, the wound bed contained 55% black eschar, 35% yellow slough, and 10% pink tissue (Figure 3A and Table 1). Negative pressure wound therapy was initiated on hospital day 15 and NCLFU therapy was initiated 2 days later to increase cellular stimulation and decrease bioburden. The wound measured 13.5 cm long by 5 cm wide by 3.5 cm deep.
On hospital day 20, the patient returned to the OR for an abdominal inspection and debridement and for revision of her ileostomy to an end-loop ileostomy. Debridement resulted in an increased wound width of 13 cm. On hospital day 27, or 7 days after combined treatment, the wound contained 1% necrotic tissue and 98% beefy red granulation tissue (Figure 3B and Table 1). Wound measurements decreased to 11.5 cm long by 13 cm wide with a depth of 3 cm. At the patient's dismissal on hospital day 30 (13 days after the initiation of combined therapy), the wound measured 10 cm long, 11 cm wide, and 2 cm in depth. The wound's area decreased approximately 37% and its volume had decreased approximately 58% in 15 days of combined therapy. She continued NPWT at her local hospital after discharge.
Case 4
A 60-year-old woman with a history of rectal cancer underwent an anterior resection and construction of a colostomy 10 years before her current hospital admission. She presented with a large parastomal hernia; the majority of her small bowel was contained in the parastomal hernia sac. On hospital day 1, she underwent surgery for a colostomy takedown, diverting loop ileostomy, and repair of the parastomal hernia. The midline abdominal wound was left open and its moist gauze dressings were changed 3 times daily. The old ostomy site was treated with both NPWT and NCLFU therapy initiated on hospital day 2. The NCLFU therapy was added to aid with liquefaction of the slough and infection control. At the start of combined therapy, the wound bed was 20% covered yellow slough (Figure 4A and Table 1). The old ostomy site measured 6.5 cm long by 2 cm wide by 1 cm deep. On hospital day 9 (7 days after the initiation of combined therapy) the slough within the wound decreased by 50% without sharp debridement and the main tissue type was red granulation tissue (Figure 4B). The patient was dismissed on hospital day 15. The old ostomy site improved to 6 cm long by 1.8 cm wide and stayed 1 cm deep. In 13 days of combined therapy, the old ostomy site decreased by 17% in both area and volume. The patient was discharged with NPWT and followed by her local primary care provider.
Discussion
Noncontact low-frequency ultrasound therapy transfers 40-kHz continuous ultrasound using atomized saline to carry the energy from the transducer to the tissues.5 Therapy is delivered without directly contacting the wound, thus avoiding thermal effects that could adversely affect edema formation. The mechanisms of action on the cells involve cavitation and acoustic microstreaming. Cavitation occurs with the production and vibration of micron-sized bubbles formed in the tissues, which lead to changes in cell function.6 Acoustic microstreaming occurs when fluids move along the sound wave boundaries, such as cell membranes, resulting in increased protein synthesis and increased permeability of the cell membranes and vascular walls.6,7 Kavros and colleagues8 discussed how increased blood flow and angiogenesis plus collagen production and alignment are associated with this form of energy application. Even after the treatment session is completed, production of tissue growth factor (a chemical mediator) continues to activate intracellular signaling pathways. In addition, ultrasonic energy is bactericidal to multiple organisms via cell wall destruction; its effect reduces quantitative bacterial counts over multiple treatments.9,10
In 1997, Argenta and Morykwas11 found NPWT effective in stimulating wound healing. This technology uses controlled subatmospheric pressure and open cell foam dressings to create a mechanical deformation of the tissues and an enhanced removal of excessive fluids. Physiologic responses to NPWT include an increase in local blood perfusion via removal of excess interstitial fluid, accelerated granulation tissue formation, increased release of growth factors in cells upregulated with stretch, increased bacterial clearance, and improved graft or flap survival.11,12 According to Orgill and associates,13 reducing tissue edema also decreases the edema within the periwound vasculature, thereby improving tissue perfusion, delivery of nutrients, and uptake of oxygen. In patients who are not medically able to launch a robust response to resist bacteria, the consistent removal of wound fluids that harbor bacteria is postulated to be beneficial to eventual healing.
In order to enhance wound healing and reduce infection risk, clinicians use a variety of treatment options. For some patients, the standard of care and the use of a single treatment modality option prove beneficial, but for others with medically complex wounds, a combined treatment regimen may be necessary. We conducted a literature review on the use of NCLFU therapy with open surgical wounds, using the databases OVID, CINAHL, and MEDLINE; retrieved references were limited to those written in English available in full-text format. We combined key words "ultrasonic MIST therapy" with "negative pressure wound therapy," using the AND Boolean function, which retrieved 42 citations. The articles contained little information on the combined effect of these therapeutic modalities since all except a single-case series (see Liguori and colleagues14) used 1 or the other modality. For our combination case series, we found increased visible granulation tissue, reduced slough within the wound bed, and reductions in wound area of up to 37% after a maximum of 18 days of treatment (Tables 1 and 2). Liguori and colleagues14 found similar results in their study, with wound area decreased by 82% to 100% but with 4 to 12 weeks of combined therapy. They showed volume reductions of 99% to 100% in that same study. By comparison, we found 16% to 62% reduction in 2.5 weeks of combined therapy.
The present case series has some limitations. The small number of cases makes it difficult to draw generalized conclusions, especially given that no posthospital follow-up was done to determine long-term outcomes. Because of its retrospective nature, not all patient parameters and measurements were controlled. Even though all of the cases had the same surgeon, the cases were not matched with like patients who had similar comorbidities; therefore, expansive conclusions cannot be drawn. In 3 of the 4 cases, sharp debridement through irrigation and debridement in the OR were necessary to remove bulk necrotic tissue that could not be accomplished quickly through autolytic debridement. Therefore, it is difficult to know how much of the improvement was due to swift removal of necrotic tissues in surgery. The healing results were positive during hospitalization at our facility, but we were unable to evaluate long-term results.
Summary
Our experience suggests that combination therapy consisting of NPWT and NCLFU therapy, with or without sharp debridement, promoted healing in selected open abdominal wounds of 4 colorectal surgical patients. We propose that NPWT, combined with NCLFU therapy, could be applied to appropriate open surgical wounds to promote wound-bed cleansing, stimulate granulation tissue formation, and enhance wound healing. Randomized clinical trials comparing the use of combination therapy are needed to determine the efficacy of combination therapy.
Key Points
* The NCLFU therapy, combined with NPWT, used in open abdominal surgical wounds resulted in improved wound healing in 4 cases.
* This combined therapy is hypothesized to promote wound-bed cleansing, stimulate granulation, and reduce the risk of infection.
* Further research is needed to confirm results of this case series.
References