Covering surgical instruments with single- or double-layer drape pending surgery: an experimental study in a perioperative setting

Background: Surgical site infections (SSI) constitute a severe threat to surgery patients. The surgical environment must be as free of contaminating microorganisms as possible. Using sterile surgical instruments while performing surgery is an absolute necessity for ensuring quality of care in perioperative settings. Aim: To compare bacterial contamination of agar plates after 15 h on set surgical instrument tables covered with a single- or double-layer drape. Methods: An experimental design was used consisting of set instrument tables with six agar plates on each table: four instrument tables were covered with a single-layer drape and four instrument tables were covered with a double-layer drape. This set-up was repeated on nine occasions during the period of data collection, making 76 set instrument tables in total. As a control, one instrument table was uncovered on four of those occasions. Results: The double-layer drape cover showed a significantly ( P = 0.03) lower number of colony forming units (CFU) per agar plate than the single-layer drape covering. As expected, the uncovered instrument tables were highly contaminated. Discussion: Our results indicate that it is good practice to cover instruments properly with at least a single-layer drape before a surgical procedure. If there is difficulty achieving optimal conditions while setting the instrument tables (e.g. positioning the patient for general anaesthesia), it is a better option to set the instrument tables earlier and cover them with a double-layer drape. These precautions will help protect the patient from harm and unnecessary SSI by lowering microbiological burden, a key factor in developing SSI.