2.1. Patient information
The study was approved by the Ethics Committee of the First Affiliated Hospital of Fujian Medical University ([2020]045). Because of the retrospective nature the requirement of informed patient consent was waived. All patients provided written informed consent for treatments they received during their hospitalization.
Hospital medical records were searched for patients from 20 to 50 years of age who were diagnosed with acute suppurative mastitis from January 2014 to December 2018, and treated with traditional I&D or VSD. The diagnostic criteria for acute suppurative mastitis were high fever, chills, breast redness and tenderness, and ultrasound confirmation of a breast abscess. Patients with co-morbid medical conditions such as diabetes mellitus, severe heart, kidney, liver, or blood diseases, malignancies or tumors were excluded. Patients with respiratory infections, gastroenteritis, cholecystitis, encephalitis, other infectious diseases, and those operated on by other surgical teams were also excluded.
2.2. Treatments
All patients were treated with antibiotics, combined with conventional I&D or negative pressure wound therapy (i.e., VSD). Acute suppurate mastitis is usually associated with a gram positive bacterial infection. The most common pathogens in acute, subacute, and granulomatous mastitis are Staphylococcus aureus, Staphylococcus epidermidis, and Corynebacteria species, respectively [8]. Thus, patients were empirically treated with a third generation cephalosporin such as cefotaxime [8]. A quinolones was used for patients with a known reaction to cephalosporins. Wound swabs were generally sent for bacterial culture and sensitivity testing, and the choice of antibiotics was then adjusted according to the culture and sensitivity results and the patient’s condition.
Patients chose which treatment they wanted after a discussion with their physician. In some cases, a patient’s decision was based on economic concerns as traditional I&D is less costly than VSD.
For analysis, patients were grouped according to those that received traditional I&D and those that received VSD. Briefly, with traditional I&D a small incision is made where the abscess is most obvious (usually after injection of a local anesthetic). The abscess contents are expressed, and the cavity is repeatedly irrigated with 0.9% saline and hydrogen peroxide. The wound is packed with gauze soaked in a chlorinated lime and boric acid solution and then covered with dry gauze. The wound packing and dressing is changed daily until the wound fully closed [9].
With VSD, a much smaller incision than that with traditional I&D is made where the abscess is most obvious (after local anesthesia is administered). The wound is debrided, and irrigated with 0.9% saline and hydrogen peroxide. It is then completely covered with polyethylene alcohol hydration foam (Guangdong Meijie Weitong Biotechnology Co., LTD, China). A semi-permeable membrane is then pasted onto the surface of the foam. Continuous negative pressure at 200 mm Hg is then connected to the membrane, and the wound is irrigated with 0.9% saline through a side tube. If the foam expands, it suggests that negative pressure aspiration is not occurring, and that there are leaks that need to be identified and repaired [10]. After 3 days, the membrane and foam are removed and the wound is inspected. Repeat debridement is performed if necessary. The foam and membrane are replaced, and VSD is begun again. The process is repeated until the wound develops healthy granulation tissue.
2.3. Outcome evaluation
Data extracted from the medical records included patient age and medical history, disease history, the number and type of abscesses, whether or not the patient was lactating, bacterial culture results, pathological results including a diagnosis of plasma cell mastitis or not plasma cell mastitis if tissue was sent for examination, the type of treatment, length of hospital stay, and length of time receiving antibiotics. As patients were discharged before wounds were completely healed, pain level at the time of wound dressing changes and the time for wound to completely heal were obtained by telephone interview.
Pain level was evaluated at the time of wound dressing changes or VSD change using a numerical rating scale (NRS) ranging from 0 to 10. A score of 0 to 3 was considered mild pain, 4 to 7 was moderate pain, and 8 to 10 was severe pain. Healing time was defined as the time from abscess drainage to complete wound closure. If patients were discharged before complete wound closure, information was obtained by telephone follow-up. The length of the hospital stay was defined as the time from admission until hospital discharge. Antibiotic treatment course was defined as the time antibiotics were begun (which was usually at admission) to the time they were discontinued. Antibiotics were discontinued when the breast mass/pain had resolved and body temperature and white blood cell (WBC) count had returned to normal.
The subgroups of patients who were lactating were also compared. That is, the outcomes of lactating women who were treated with I&D were compared with lactating women who were treated with VSD.
2.4. Statistical analysis
The Kolmogorov-Smirnov method was used to detect the normality of the data. Categorical data were expressed and number and percentage, and comparisons between 2 groups were performed with Fisher’s exact test when the number in the table was < 40, and the chi-square (c2) test when number was > 40. Continuous data were expressed as mean ± standard deviation, and normally distributed data were compared with the t test. Non-normally distributed data were presented as median and interquartile range (IQR), and examined with the Wilcoxon rank sum test. Statistical analyses were performed with SPSS version 19.0 software (SPSS Inc., USA). Values of p < 0.05 were considered to indicate statistical significance.