Are three antiseptic paints needed for safe preparation of the surgical field? A prospective cohort study with 239 patients

Background: Preoperative skin antisepsis is an essential component of safe surgery. However, it is unclear how many antiseptic paints are needed to eliminate bacteria prior to incision. This study compared microbial skin counts after two and three antiseptic paints. Methods: We conducted a prospective cohort study in non-emergency patients receiving a cardiac/abdominal surgery with standardized, preoperative skin antisepsis consisting of an alcoholic compound and either povidone iodine (PI) or chlorhexidine (CHX). We obtained three skin swabs from the participant's thorax/abdomen using a sterile template with a 25 cm2 window: After collection of the first swab prior to skin antisepsis, and once the second and third application of PI/CHX had dried out, we obtained a second and third swab, respectively. Our primary outcome was the reduction in microbial skin counts after two and three paints of PI/CHX. Results: Among the 239 enrolled patients, there was no significant difference in the reduction of mean square root-Transformed microbial skin counts with three versus two paints (P = 0.2). But distributions of colony forming units (CFUs) decreased from paint 2 to 3 in a predefined analysis (P = 0.002). There was strong evidence of an increased proportion of patients with zero CFU after paint 3 versus paint 2 (P = 0.003). We did not identify risk factors for insufficient reduction of microbial skin counts after two paints, defined as the detection of > 5 CFUs and/or ≥ 1 pathogens. Conclusions: In non-emergency surgical patients, three antiseptic paints may be superior to two paints in reducing microbial skin colonization prior to surgery.