A prospective analysis of postoperative surgical site infection and factors affecting it, including the preoperative HbA1C and fasting blood glucose level, in patients undergoing elective breast oncological surgery.

Methodology

Institutional Ethics committee approval will be sought. Clinical Trials Registry of India (CTRI) registration will be done.Data will be collected from the electronic medical record (EMR) system of the hospital which has the patient’s clinical and laboratory data.

Following details will be collected from all patients -demographic data(age,sex,body mass index),smoking status, tobacco use,preexisting comorbidities and their treatment, American Society of Anesthesiologists (ASA) classification,Eastern Cooperative Oncology Group(ECOG)status,primary diagnosis, stage of disease,clinical details including preoperative chemotherapy, radiotherapy, indication for surgery,type of surgery(type of mastectomy (modified radical mastectomy [MRM] vs breast conservation surgery[BCS]),reconstruction – pedicled flap or free flap, type of axillary surgery (sentinel node biopsy/ axillary sampling/ axillary node dissection),duration of surgery, etc.Patients with high fasting (>110mg/dl) or postprandial(>140mg/dl) coming for Pre anaesthetic checkup (PAC) will be identified and sent for physician reference for definitive diagnosis and to start medications.As per routine practice, preoperative HbA1c levels (within 1 month of date of surgery) will be checked in all patients with diagnosed diabetes mellitus or in patients with high fasting (>110mg/dl) or postprandial (>140 mg/dl) blood glucose level.The fasting blood sugar level (FBS) on the day of surgery will be noted.

SSI will be checked on postoperative day 1, 14, 30 and 90 days. The term surgical site infections (SSI)constitutes an umbrella term which includes superficial incisional SSI, deep incisional SSI, wound dehiscence, donor site infections, flap complications. These SSI measured will include documented surgical complications within ninetydays of surgery including: urgent or emergent return to the operating room (OR), breast or donor site seroma (as defined by clinically evident fluid collection requiring aspiration), hematoma requiring surgical evacuation, infection treated with oral or intravenous antibiotics or surgical washout, mastectomy skin flap or nipple necrosis requiring serial dressing changes or clinic/OR debridement, symptomatic fat necrosis requiring debridement, partial flap necrosis (requiring serial dressing changes or debridement), delayed wound healing (requiring serial dressing changes >3 weeks from surgery or debridement and closure), and flap complications (fat necrosis, mastectomy flap necrosis, hematoma, seroma, thrombosis, partial flaploss, total flap loss, wound infection, wound dehiscence, thrombotic events).Also, length of ICU& hospital stay,days on ventilator,90-day morbidity &mortality,90-day re-surgery and 90-day readmissions will be assessed.Complications during hospital stay including gastrointestinal, cardiovascular, renal, respiratory, infections(urinary tract infections,pneumonia,sepsis), etc will be included in the analysis. Allcomplications after surgery including surgical site infections will be graded using Clavien Dindo classification.

The current antibiotic protocol followed by breast servicesis to give 2 shots of intravenous antibiotics(Cefuroxime) for all cases(one before incision and one shot postoperative period.For all cases undergoing oncoplasties, antibiotics are given for a total of 5 days(orally from postoperative day 1).Incase of infection, hematoma, flap necrosis or any other SSI within the first 30 days post-op, empirical antibiotics are started which is usually for gram positive cover along with culture sensitivity.The antibiotics are then changed as per culture and sensitivity report.

Sample size:

Convenient sample size of 6 month’s duration

 Statistical Analysis Plan

·         Clinical and patient related factors will be compared between patients who developed surgical site infection (SSI) within 90 days after breast surgery to patients who did not.

·         The mean and standard deviation will be used for continuous variables that had a normal distribution and were compared using the two-sample t-test. The continuous variables that are not normally distributed will be reported using the median and interquartile range and will be compared using the Wilcoxon rank-sum test. Categorical variables will be reported as frequencies and percentages and will be analysed by Chi-square or Fisher’s exact test as appropriate.

·         To determine a threshold HbA1c level and fasting BSL on the day of surgery to predict 90-day SSI, ROC curve will be plotted and the best cut-off will be obtained through Youden’s Index.

·         Binary logistic regression will be used to evaluate the influence of independent risk factors on the development of SSI after breast surgery, especially pre-operative Hb A1C and fasting BSL. This will be reported using the odds ratio (OR) with a 95% confidence interval (CI).

·         The 90 days SSI free probability was calculated from the date of surgery using the Kaplan-Meier method and assessed using the log-rank test. Factors like pre-operative HbA1C and fasting BSL along with patient related and clinical factors will be assessed for 90 days SSI free probability. Multivariate analysis using Cox regression will be carried out to assess factors that predict independently the 90 days SSI free probability.

•         Statistical analyses will be performed using SPSS (the statistical package for social sciences) (version 26.0, SPSS Inc, Chicago, IL, USA)