Closed incision prophylactic negative pressure wound therapy in patients undergoing major complex abdominal wall repair

This was a retrospective before–after comparison nested in a consecutive series of patients undergoing CAWR at the Department of Surgery of the Academic Medical Center in Amsterdam, a tertiary university hospital in the Netherlands. The medical ethical committee of the hospital approved the study and for this type of study, formal consent was not required. Starting January 2014, the use of pNPWT for patients undergoing complex abdominal wall repair became a standard part of the procedure. To minimize selection bias, we compared two periods of 14 months before and 14 months after January 2014 to assess the effects of pNPWT. All data on operations performed between September 2012 and April 2015 by a single surgeon, more than 10 years specialized in complex abdominal wall surgery and lead of a specialized outpatient clinic for acute intestinal failure, were reviewed. Primary outcome was the incidence of superficial and deep wound infections. The wound infections were further subdivided into incisional wound infections and/or subcutaneous abscesses. Secondary outcomes were the appearance of other wound complications such as non-infected seroma, bleeding or hematoma, skin- or fat necrosis, wound dehiscence requiring (prolonged) NPWT, anastomotic leakage, intra-abdominal abscesses, ECF, the need for percutaneous or surgical interventions, emergency department visits after discharge, re-admissions and 30-day mortality. All adult patients undergoing midline elective open, CAWR according to the criteria of major complex abdominal wall surgery as described by Slater in 2014 [2] were included. Primary skin closure at the end of surgery (with or without flap rotation by a plastic surgeon) was a prerequisite. Data on patient demographics, risk factors for SSI, level of contamination, operative characteristics and post-operative complications (including SSI) were extracted from the clinical charts.

Infections were scored from the clinical charts after the operative procedure and classified according to the Centre for Disease Control (CDC) SSI criteria (including superficial, deep and organ space infections). Next to this, superficial wound infections according to the CDC SSI criteria were scored for subcutaneous abscess and/or incisional wound infection. In case a culture was available these results were used, if no culture was available information from the clinical chart was used. The description of purulent drainage from a superficial incision or the need of opening the wound by the surgeon due to pain or tenderness, localized swelling, erythema or heat was scored as positive for wound infection. In case of bowel content leakage from either the anastomosis or bowel perforation which was proven by contrast radiography or relaparotomy, this was scored as leakage. If there was an unnatural communication between the gastro-intestinal tract and the skin, it was registered as an ECF. Intra-abdominal fluid collections with positive culture after drainage without signs of anastomotic leakage or bowel perforation were scored as an intra-abdominal abscess. Wound dehiscence needing postoperative therapeutic NPWT was recorded separately in the control group as well as in the pNPWT group. For the pNPWT group, this element was scored if NPWT was continued, after the first dressing change at postoperative day 5, because of dehiscence during pNPWT. Continuing pNPWT at the dressing change at postoperative day 5 because of severe edema but without any signs of dehiscence or infection was not scored as SSI. Bleeding or hematoma was recorded in the case of either active bleeding or a large hematoma, which needed radiologic drainage. We defined seroma as a subcutaneous fluid collection without any signs of infection or with negative culture results after drainage. Infected seroma was scored as a superficial SSI. Interventions were scored separately for intra-abdominal and extra-abdominal. Intra-abdominal interventions could be either radiologic percutaneous drainage or relaparotomy. Extra-abdominal interventions were scored for radiologic percutaneous subcutaneous drainage and the need for opening of the wound with or without antibiotics. Opening of the wound could be either spontaneously due to infection or as part of therapeutic drainage. Interventions were scored for infectious complications as well as non-infectious complications.

Operative principles for CAWR did not change over the study period apart from the application of pNPWT. Infection prevention was performed according to the national guidelines and included hand hygiene, surgical site preparation with an alcohol and chlorhexidine based, non-aqueous, antiseptic agent and systemic prophylactic antibiotics 30–60 min before incision. In case of presence of ECF segmental intestinal resection was performed. All patients had hand-sewn anastomoses. In patients where primary fascial closure was not possible, an open anterior CST was performed. An intra-abdominal sublay biological mesh (Strattice™ porcine dermal matrix, Acelity) was used in all cases with enterocutaneous or enteroatmospheric fistula and sometimes in other contaminated situations, such as infected synthetic mesh removal. In clean situations, a synthetic retrorectus light-weight polypropylene sublay Vypro^® mesh (Ethicon/Johnson&Johnson) was used. Sometimes, in very large clean abdominal wall defects a double layer technique was used, including intra-abdominal sublay Strattice ™ dermal matrix and retrorectus light-weight polypropylene sublay Vypro^® mesh, combined with a CST. On average, three 18 Fr suction drains were used—1 subfascial on top of the biological mesh and 2 subcutaneous—to ensure active drainage of fluids and these were only removed when production was <30 ml/24 h. The fascia was closed with a monofilament polydioxanone suture (PDS loop). In case of large full thickness skin defects, a plastic surgeon performed a flap reconstruction. No skin grafts were used. All patients had subcutical closure before the skin was closed. The skin was closed with single polyester Mersilene^® sutures (Ethicon); no staples were used. Up to January 2014, elastic Microfoam surgical bandage (3 M) was applied for 24 h. From January 2014, pNPWT (either Prevena™ (Acelity/KCI) or a home-made construction of Melolin non-adhesive wound dressing (Smith&Nephew) and V.A.C^® Granufoam™ (Acelity/KCI) was used for at least 5 days with a negative pressure of 100 mmHg. After 5 days, the surgical team performed wound inspection. In case of severe edema and/or risk of wound dehiscence due to abdominal distension, pNPWT dressing was changed and prolonged for another 3–5 days. In case of a closed wound without any signs of edema or dehiscence, the pNPWT was removed. All patients wore a binder for 7 days continuously and thereafter for 3 months postoperative when mobilizing.

The pNPWT and the control group were compared using Chi-square (Fisher exact) test for categorical data and using Mann–Whitney U test for not normal distributed numerical variables. Normal continuous numerical variables were compared using Students t test only if found normally distributed in a Q–Q plot. Statistical analyses were performed with SPSS version 21.0. A p value ≤ 0.05 was considered statistically significant.

During the 14-month period, from January 2014 until April 2015, 32 consecutive patients undergoing CAWR fulfilled the inclusion criteria and were treated with pNPWT. In the preceding 14 months, between September 2012 and January 1st 2014, a consecutive group of 34 patients formed the control group. Of these 66 consecutive patients, 36 (55%) were male, and the mean age at the time of operation was 59.4 [standard deviation (SD) 13.3] years. Baseline characteristics regarding co-morbidity known for increased risk of SSI, such as obesity or inflammatory bowel disease (IBD), did not significantly differ between both groups (Table 1). Overall, almost half of the included patients (44%) depended on PN. Seventy-seven percent (51/66) of the operations involved clean-contaminated or contaminated or dirty operations. The median number of previous abdominal surgeries was 4 (range 1–24). In 91% of the patients, a CST was performed, usually on both sides. Mean operation time (including anesthesia) was 438 (SD 153) minutes. Surgery was performed for the following reasons: resection of one or more enteric fistulas, restorations of bowel continuity, very large or recurrent hernias or recurrent hernia with infected mesh. Reconstruction by a plastic surgeon was required in 12 cases (18%). In Table 1, we summarize patient and operative characteristics for both the pNPWT and the control group. There were no statistical significant differences in operative characteristics between the two groups.

Table 2 summarizes outcomes of both groups. Overall SSI rate (including organ-space infections) was 47%. Six patients developed anastomotic leakage. In these patients, it was not possible to judge SSI; thus, these six patients were excluded from the wound infection analysis. The wound infection rate was 38% (23/66). We had no deep SSI. We found a significant decrease in superficial wound infections after surgery in the pNPWT group compared with the control group (24 versus 51%, p = 0.029, OR 0.30 (95% CI 0.10–0.90)). The number of incisional wound infections significantly decreased after the introduction of pNPWT (7 versus 48%, p < 0.001, OR 0.08 (95% CI 0.02–0.39)), while the number of subcutaneous abscesses was comparable (5 versus 4). In the pNPWT group, all wound infections involved contaminated operations, whereas an additional three patients had wound infections after clean surgery in the control group. The number of patients needing subcutaneous drainage was comparable in both groups (22 versus 24%). However, (the need for) opening of the wound with or without antibiotics was significantly decreased after the introduction of pNPWT (7 versus 48%, p < 0.001, OR 0.08 (95% CI 0.02–0.39). The need for postoperative intra-abdominal interventions was comparable in both groups, including two relaparotomies for anastomotic leakage in the control group and 9 and 8 radiologic drainages, respectively, in intervention and control group. Six patients in the control group needed NPWT due to wound dehiscence compared with seven patients in the pNPWT group needing prolonged NPWT.