INTRODUCTION

Surgical site infection (SSI) is a common complication in postoperative abdominal surgery that is important to prevent because it can prolong hospital stay and increase medical costs.^{1, 2} The incidence of SSI following emergency laparotomy is reported to be 25–40% higher than that for elective surgery, and it increases even more with contaminated surgery.^3-5

Although prophylactic open negative pressure wound therapy (NPWT) for contaminated surgical incisions with a high risk of SSI and delayed suturing has been reported to be effective, delayed wound healing with open NPWT remains a problem.^{6, 7} The efficacy of closed NPWT for primary suture wounds in elective and emergency surgery with a higher risk of SSI has been reported for the prevention of SSI, but its usefulness in emergency contaminated abdominal surgery remains to be clarified.^7-9 We hypothesized that closed NPWT would contribute to a reduction in the incidence of SSI and introduced closed NPWT to prevent SSI in primary sutured wounds following the performance of emergency laparotomy from May 2019.

This study aimed to evaluate the prophylactic effect of closed NPWT against SSI after emergency contaminated abdominal surgery for gastrointestinal perforation by comparing the incidence of SSI between closed NPWT and a conventional wound protection method.

METHODS

Study design, settings, and population

This single-center, retrospective, observational study was carried out in Kansai Medical University Hospital Critical Care and Emergency Center (Hirakata, Japan), a tertiary emergency medical center. The patients' electronic medical records were reviewed retrospectively. This study was conducted in accordance with the Declaration of Helsinki and was approved by the Ethics Committee of Kansai Medical University (approval no.: 2024193).

The patients were divided into two groups, the closed NPWT group, which comprised patients whose primary wound closure was with closed NPWT managed using the PICO 7™ device (Smith and Nephew Healthcare, Hull, UK) between May 2019 and May 2024, and the standard dressing group, which comprised patients who underwent incisional wound management with a standard surgical dressing between January 2016 and April 2019. The wounds of both groups were washed with 200–300 mL of saline prior to wound closure. In the standard dressing group, wounds were stapled at a pitch of 1 cm, whereas in the closed NPWT group, they were loosely sutured with interrupted sutures or stapled at a pitch of 2–3 cm.

Patients who underwent emergency laparotomy for gastrointestinal perforation with Centers for Disease Control and Prevention (CDC) wound classifications of 3 (contaminated) and 4 (dirty) in midline laparotomy incisions or pararectal incision between January 2016 and May 2024 were included in this study. Patients who met at least one of the following criteria were excluded: open abdominal management, reoperation within 7 days, or inoperable due to advanced cancer. Cases with closed NPWT of less than 3 days were also excluded from the analysis in reference to previous studies (Figure 1).^{10, 11}

Data collection and outcomes

Patients were analyzed for demographics, risk factors for wound complications, clinical characteristics, operative indications, and CDC wound classification. Patients were diagnosed as having disseminated intravascular coagulation (DIC) by Japanese Association for Acute Medicine DIC criteria.

The primary outcome was the incidence of superficial and deep SSI at the last visit or 30 days postoperatively. The secondary outcomes were the length of intensive care unit (ICU) stay and hospital stay, in-hospital mortality, and incidence of complications as assessed by Clavien-Dindo grade. Wounds were managed with the PICO 7 device (Figure 2), which is designed to provide NPWT to wounds that have been sutured or stapled closed. In Japan, the PICO7 device can be used only at facilities that charge a specific hospitalization fee, such as a specific ICU management fee, for surgical wounds with a high risk of SSI, as covered by insurance. The PICO 7 dressing was placed at the time of wound closure, removed once on postoperative day 3, and if there were no findings of SSI after checking the wound, the PICO 7 dressing was re-applied and closed NPWT was continued until postoperative day 7 at the longest. The device was then removed, and the wound was left open to air or covered with dry gauze. If closed NPWT could not be maintained for 3 days for any reason, the closed NPWT device was replaced if the wound showed no complications. The PICO 7 dressing was changed once.

RESULTS

DISCUSSION

This study showed that closed NPWT was significantly associated with a lower incidence of superficial and deep SSI after emergency laparotomy for gastrointestinal perforation. Several previous studies have suggested the prophylactic effect of closed NPWT for emergency contaminated surgery. However, to the best of our knowledge, this is the first study to show the prophylactic effect of closed NPWT against SSI after laparotomy for gastrointestinal perforation only. The results suggest that the use of prophylactic closed NPWT may be an option for the prevention of SSI after laparotomy for gastrointestinal perforation.

Closed NPWT exerts effects on wound healing through several mechanisms. Closed NPWT decreases lateral tension and dead space and reduces seroma formation. It also eliminates excess tissue edema, increases lymphatic drainage and blood flow around the closed incision, and releases local growth factors to promote healing of the surgical incision and prevent complications.^12-15 On the basis of an extensive literature review, an international interdisciplinary consensus recommends the use of closed NPWT in patients at high risk for SSI.¹⁶ Previous studies have reported that closed NPWT is useful in elective and emergency colorectal surgery with a high risk of SSI, but some randomized controlled trials have reported no effect, so it is important to identify patients for whom closed NPWT will be beneficial.^{3, 7-9, 17, 18} High risk for SSI is defined in terms of wound class, patient comorbidities, and preoperative condition. In this study, the CDC target wound class was that of 3 or higher. Furthermore, patients with ASA-PS class of 3 or higher are considered to be at high risk of developing SSI, but in this study, more than 70% of the patients were of ASA-PS class 4.¹⁹ The present study showed that closed NPWT may contribute more to a reduction in SSI in patients at highest risk for SSI than was shown in previous studies.

Due to the higher rate of SSI in contaminated and dirty wounds, many surgeons opt to leave the wound open for healing by secondary intention or by delayed primary closure.²⁰ Management of open surgical wounds with NPWT has now become commonplace in the treatment of contaminated wounds. Open NPWT and delayed suturing have been reported to be effective in emergency surgery for colorectal perforation.^{6, 21} However, several problems have been pointed out in regard to open NPWT and delayed primary closure. The use of open NPWT may lead to longer wound healing and hospitalization times and patient discomfort until the open wound is closed. In addition, open NPWT results in additional healthcare costs, and delayed primary closure requires wound closure under local anesthesia, with dressing changes needed two or three times a week. Frazee et al., in a prospective, randomized trial comparing open NPWT to closed NPWT for contaminated surgery, showed that closed NPWT healed wounds faster than open NPWT without wound complications, and in terms of cost, they stated that closed NPWT may be less expensive than open NPWT.⁷ We were not able to examine cost in the present study, and we could not find any difference in the length of hospital stay because of the high ASA-PS class and the severity of the study patients' conditions, as many of them required transfer to other hospitals, making the length of hospital stay not easily comparable. However, closed NPWT offers the possibility of rapid wound healing while minimizing short-term discomfort for the patient and potentially reducing medical costs compared to open NPWT.

The optimal duration of therapy for closed NPWT and the optimal negative pressure to be applied on a closed incision have yet to be determined because there are few data on closed NPWT after contaminated surgery. There are two main devices that can be used for closed NPWT, but each device uses different pressure settings: for example, PREVENA™ (3M Company, San Antonio, TX, USA) recommends a pressure setting of −125 mmHg, but that of the PICO 7 is −80 mmHg. The duration of closed NPWT in this study was not constant as it ranged from 3 to 7 days because some patients required earlier-than-planned replacement due to poor application of negative pressure. We used the PICO 7 device because device set-up and use are easy, its size is suitable for the size of the laparotomy wound, and the canister is free and easy to carry. In addition, the work of the medical staff may be reduced because the dressing only needs to be changed once before the end of closed NPWT, and it is easy to change and manage. However, the disposable canister has a fixed capacity and may cause early failure of negative pressure in severe cases with large amounts of leachate. This study excluded surgeries requiring open abdominal management in conjunction with damage control surgery, and it is unclear whether closed NPWT would be useful in such very severe cases. This will require further study.

LIMITATIONS

Several limitations of this study should be considered when interpreting its results. First, this study is of a retrospective observational design performed at a single center with a small sample size. For a more thorough analysis, a larger multicenter study is required. Second, although the diagnosis of SSI was based on CDC criteria, it was made subjectively by the attending surgeon and evaluated retrospectively from the patient's electronic medical record. This might have resulted in some risk of bias. Third, the duration of application of closed NPWT was not constant, and the method of general wound management, such as dressing and washing, was not protocolized but was determined based on the preference of the attending surgeons. Finally, we did not perform an economic evaluation to determine the cost-effectiveness of NPWT compared with standard surgical dressing.

CONCLUSION

The application of closed NPWT in patients undergoing laparotomy for gastrointestinal perforation was associated with a lower incidence of SSI compared with that of standard surgical dressing. Closed NPWT may be an option for the prevention of SSI after gastrointestinal perforation. Further prospective analyses with a larger number of patients are required.

CONFLICT OF INTEREST STATEMENT

The authors declare no conflicts of interest. Dr. Yasuyuki Kuwagata is an editorial board member of the Acute Medicine & Surgery journal and a co-author of this article. To minimize bias, this author was excluded from all editorial decision-making related to the acceptance of this article for publication.

ETHICS STATEMENT

Approval of the research protocol: The Ethics Committee of Kansai Medical University approved this retrospective study (approval no.: 2024193).

Informed consent: The need for informed consent was waived because of the observational nature of the study and the requirement for no treatment beyond daily clinical practice (Ministry of Education, Culture, Sports, Science and Technology, and Ministry of Health, Labor and Welfare, Japan; Ethical Guidelines for Medical and Health Research Involving Human Subjects).

Registry and the registration no. of the study/trial: Not applicable.

Animal studies: Not applicable.