Effect of aqueous olanexidine versus alcohol-based chlorhexidine for surgical skin antisepsis on incidence of surgical site infections in gastrointestinal surgery: multicentre randomised controlled clinical trial (OEDO trial) protocol.

INTRODUCTION: Surgical site infections (SSIs) are among the most common nosocomial infections in surgery patients. Two types of preparations, povidone-iodine and chlorhexidine-alcohol, are commonly used in preoperative antiseptic procedures worldwide. However, there are inconsistencies among international guideline recommendations concerning skin antiseptics. This trial aimed to evaluate the superiority of olanexidine, which reduced SSI rates more than povidone-iodine in our previous randomised trial, over chlorhexidine-alcohol in clean-contaminated surgery. METHODS AND ANALYSIS: This multicentre randomised controlled clinical trial will compare two antiseptics (1.5% olanexidine and 1.0% chlorhexidine-alcohol) to prevent SSI in clean-contaminated gastrointestinal surgeries with surgical wounds. On providing consent, patients aged <18 years will be included. The primary outcome will be the postoperative 30-day overall SSI rate, while the secondary outcomes will be the postoperative 30-day superficial incisional SSI rate, deep incisional SSI rate, organ/space SSI rate, positive bacterial wound culture rate, cultured bacterial strains, rates of intervention-related toxicity and allergic events (eg, erythema, pruritus, dermatitis and other symptoms of allergy around the region disinfected by the antiseptic during surgery), rate of reoperations due to SSI, medical economic effect indicators (based on health insurance claims) and hospital duration. The Mantel-Haenszel method will be used to estimate the adjusted risk ratio and its 95% CI for the primary analysis, which will compare the treatment effects. ETHICS AND DISSEMINATION: The protocol was approved by the Institutional Review Board of Keio University School of Medicine and subsequently by the board of each participating site. Participant recruitment began in January 2023. The final results will be published in medical journals after international peer review. TRIAL REGISTRATION NUMBER: UMIN000049712.