Supplementary Material for: Reducing Surgical Site Infection by Prophylactic Negative Pressure Wound Therapy in a Cohort of General Surgery Patients

<b><i>Background:</i></b> Surgical site infection (SSI) is one of the leading complications in health care. Negative pressure wound therapy (NPWT) is meanwhile widely prophylactically used for preventing SSIs. For evaluating the results of the implantation of this technique, we used the Simon single-arm study design and examine whether NPWT has a prophylactic effect on reducing SSIs in a cohort of general surgery patients. <b><i>Methods:</i></b> This single-arm, two-stage study includes 81 elective general surgery patients and corresponds to the Simon’s design. The sample size calculation was based on a reduction in the superficial SSI rate from 12 to 4% (power 80%, significance level 5%) using a NPWT system. In compliance with Simon’s two-Stage design, the study required the recruitment of 34 patients in stage I and 47 patients in stage II. The two-stage design method would be discarded in case of a wound infection in 3 or more patients in stage I or 6 or more patients in stage II. Using the NPWT system in the operating room, a negative pressure wound dressing was applied post-operatively and removed after 7 days. According to the criteria of the Centres for Disease Control and Prevention (CDC), post-operative wound documentation followed on day 7 and 30. <b><i>Results:</i></b> In stage I, no SSI was apparent. In stage II, 3 patients had SSIs (CDC grade I). <b><i>Conclusion:</i></b> A prophylactic NPWT can significantly reduce the wound infection rate in elective general surgery.