Patients
We included patients who had undergone laparoscopic appendectomy due to acute appendicitis from March 2017 to October 2019 from three hospitals. All patients were diagnosed with acute appendicitis by abdominopelvic computed tomography (APCT) scan. We excluded patients who needed open appendectomy or open conversion after laparoscopic approach owing to severe inflammation or adhesion during the operation. Patients under 18 years old were also excluded. To minimize the confounding effect derived from different types of skin preparation solution, only patients who underwent skin preparation with PI were included. Laparoscopic appendectomies were performed by four experienced colorectal surgeons. Finally, a total of 333 patients were included in the analysis.
We divided 333 patients into three groups according to the method of wound irrigation during laparoscopic appendectomy: no irrigation (n = 93), saline irrigation (n = 144), and PI (n = 96) groups (Fig. 1). The suturing technique was adopted according to the surgeon’s discretion, i.e., stapler, vertical matrix suture with nylon, or subcuticular suture with absorbable materials. Absorbable sutures were used for approximation of the fascia, and the subcutaneous space was irrigated with saline or PI.
Clinical data were retrospectively collected, such as sex, age, American Society of Anesthesiologists (ASA) physical status classification [10], and body mass index (BMI). Preoperative laboratory findings were reviewed, including white blood cell (WBC) count (⋅10³/µL) and hemoglobin (g/dL), albumin (g/dL), C-reactive protein (CRP) (mg/dL), and erythrocyte sedimentation rate (ESR) (mm/hr) levels. The presence of fever was defined as body temperature higher than 37.8℃. Both preoperative fever and postoperative fever were recorded. Operative data including operation time, presence of perforated appendicitis, the method of wound irrigation, wound closure, and umbilical skin incision were also collected.
SSIs were defined according to the criteria of the National Nosocomial Infection Surveillance System (NNIS) by the Centers for Disease Control and Prevention(CDC) [11, 12], which can be superficial, deep, and organ/space SSI. Superficial incisional SSI involves only the skin and subcutaneous tissue. Deep incisional SSI involves deep tissues, such as fascial and muscle layers, and organ/space SSI involves any part of the organs’ anatomy and spaces that are incised, which were opened or manipulated during operation [13].
Waiver of informed consent was approved by the Institutional Review Boards (AJIRB-MED-MDB-20-030, NHIMC 2020-04-031, UC20RASI0043).
Statistical analysis
Categorical variables were analyzed using chi-square or Fisher’s exact test. Continuous variables were analyzed using Student’s t-test. Data were presented as number (%) or mean ± standard deviation. Univariate logistic regression analysis was done to identify risk factors associated with SSI. P < 0.05 was considered statistically significant. Statistical analysis was done using IBM SPSS ver. 20.0 (IBM Co., Armonk, NY, USA).