As a result of laser imaging studies in an ultraclean theatre we concluded that obstructions to horizontal airflow at the periphery might produce areas of high particulate residence times. High residence times may allow a higher proportion of infected particles to land. We decided to investigate this effect by placing settle plates in defined positions on instrument trays during surgery. In an initial study contamination was 0.25 colonies/plate/hour. When the surgeon, assistant and scrub person all used a body exhaust system the contamination rate was 0.04 colonies/plate/hour. We then organised the instrument tables with two large tables orientated so that the scrub person did not have to stand between the airflow and the table. We placed plates on both trays with the locations recorded. With the instrument trolleys in optimised positions the contamination rate remained consistently at 0.04 colonies/plate/hour. An animation was produced showing how the bacterial colonies appeared over 18 hours of surgery. The majority of the contamination occurred on the surgeons’ side trolley at the opposite end of the trolley to the surgeon. Ultraclean enclosures in the UK are specified by HTM03-01, which sets a standard of <10 cfu/cubic meter measured by active air sampling. The measurement does not however take place during surgery, as it is very difficult to perform air sampling during surgery. There is a reasonable correlation between air contamination and settle plates so they are a viable method for during surgery monitoring. In a modern operating enclosure, using body exhausts, our contamination rate compares favourably to the fourth phase of Charnley's classic study in which he used 300 air changes/hour in the prototype closure. The rate compares favourably to the multi-centre Italian GISIO-ISChIA study. The contamination rate achieved could form a basis for comparative audits based on realistic during surgery monitoring

Introduction. One method of surgical site infection prevention is lowering intraoperative environmental contamination. We sought to evaluate our hospitals operating room (OR) contamination rates and compare it to the remainder of the hospital. We tested environmental contamination in preoperative, intraoperative and postoperative settings of a total joint arthroplasty patient. Materials & Methods. 190 air settle plates composed of trypsin soy agar (TSA) were placed in 19 settings within our hospital. Locations included the OR with light and heavy traffic, with and without masks, jackets, and shoe covers, sub-sterile rooms, OR hallways, sterile equipment processing center, preoperative areas, post-anesthesia care units, orthopaedic floors, emergency department, OR locker rooms and restrooms, a standard house in the local community, and controls. The plates were incubated in 36 degrees celsius for 48 hours and colony counts were recorded. Numbers were averaged over each individual area. Results. The highest CFU was the OR locker room at 28 CFU/plate/hr. Preoperative & post anesthesia care unit holding areas were 7.4 CFU & 9.6 CFU, respectively. The main orthopaedic surgical ward had 10.0 CFU/plate/hr, while the VIP hospital ward had 17.0 CFU/plate/hr. The OR environment all had low CFUs. A live OR had slightly higher CFUs than ones without OR personnel. The OR sub-sterile room had 5.2 CFU/plate/hr, and the OR hallway had 11.2 CFU/plate/hr. The local community household measured 5.6CFU/plate/hr. Discussion. In comparison to the local community household, the OR locker room, restrooms, hospital orthopaedic wards, ED, pre-operative holding, PACU and OR hallway all had higher airborne contamination than the local household in our surrounding community. We were surprised to find some areas with high rates of contamination. Our hospital has since increased environmental cleaning and monitoring of these areas with improved effect. Based on our results, we can recommend environmental sampling as a simple, fast, inexpensive tool to monitor airborne contamination

Deep infection occurs in 2–4% of lower limb arthroplasty resulting in increasing cost, co-morbidity and challenging revision arthroplasty surgery. Identifying the potential sources of infection helps reduce infection rates. The aim of our study is to identify the impact and potential for contamination of our hands and gowns whilst scrubbing using SSHS. A colony-forming unit (CFU) is a pathogenic particle of 0.5 micrometers to 5 micrometers. Concurrent particle counts and blood agar exposure settle plates for 3 subjects and 1 alcohol cleaned mannequin; testing a standard arthroplasty hood, a SSHS with and without the fan on for a 2 minute exposure to represent scrubbing time. Microbiological plates were incubated using a standard protocol by our local microbiology department. All SSHS were positive for gram-positive cocci with a mean colony count of 410cfu/m. 2. Comparing background counts for laminar flow (mean 0.7 particle/m. 3. ; 95% CI 0–1.4) versus scrub areas (mean 131.5 particle/m3; 95% CI 123.5–137.9; p=0.0003), however neither grew any CFU's with a 2-minute exposure. For the mannequin, the only significant result was with the fan on with a 1.5× increase in the particle count (p=0.042) and a correlating positive organism (13CFU/m. 2. ). With human subjects, however, the particle count increased by 3.75× the background count with the fan on (total p=0.004, CFU p=0.047) and all had positive cultures, mean 36 CFU/m. 2. There were no positive cultures with the standard arthroplasty hood or the SSHS with no fan on. If repeated in laminar flow, there was only a statistically significant increase with the fan on (p=0.049), but with negative cultures following a 2-minute exposure. Sterile gloves and gowns can be contaminated when scrubbing with the SSHS fan on. We recommend having the fan switched off when scrubbing until the hood and gown is in place, ideally in a laminar flow environment