Visibility of surgical site marking: A prospective randomized trial of two skin preparation solutions

Background: An important component of the surgical time-out is to confirm surgical site skin markings to prevent wrong-site surgery. Different skin preparation solutions may have variable effects on the visibility of site markings after application. We performed a prospective randomized clinical trial to quantitatively and qualitatively evaluate the visibility of surgical site markings after the use of two commonly available skin preparation solutions. Methods: We enrolled twenty patients undergoing primary total hip arthroplasty at our institution. Preoperatively, a black permanent marker was used to mark the skin of each patient with a random combination of three letters, underlined by a single black line, and with the surgeon's initials. Patients were randomly selected to receive a chlorhexidine-based or an iodine-based skin preparation according to manufacturer guidelines. The skin markings were photographed digitally, before and after the application of solution. The photographs made after the application of solution were assessed quantitatively, by calculating the contrast (marker to skin) before and after the application of the solutions, and qualitatively by ten orthopaedic surgeons to identify the random initials and to recognize skin markings. Results: The mean change in contrast level after application of the chlorhexidine-based solution was significantly greater than that after application of the iodine-based solution (mean and standard deviation, 59.8 ± 15.7 U versus 14.9 ± 11.4 U, respectively; p < 0.0001). Surgeons were an average of twenty-two times less likely (95% confidence interval, eight to sixty-eight) to judge markings as acceptable for site identification after preparation with the chlorhexidine-based solution than after preparation with the iodine-based solution. When examining individual letters, the surgeons correctly identified 296 of 300 letters in the group prepared with the iodine-based solution and 209 of 300 letters in the group prepared with the chlorhexidine-based solution; the difference was significant (p < 0.0001). Conclusions: The use of the chlorhexidine-based solution for skin preparation resulted in significantly greater erasure of the surgical site marking than did the use of the iodine-based solution. Level of Evidence: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.