The critical relationship between airborne microbiological contamination in an operating theatre and surgical site infection (SSI) is well known. The aim of this annotation is to explain the scientific basis of using settle plates to audit the quality of air, and to provide information about the practicalities of using them for the purposes of clinical audit. The microbiological quality of the air in most guidance is defined by volumetric sampling, but this method is difficult for surgical departments to use on a routine basis. Settle plate sampling, which mimics the mechanism of deposition of airborne microbes onto open wounds and sterile instruments, is a good alternative method of assessing the quality of the air. Current practice is not to sample the air in an operating theatre during surgery, but to rely on testing the engineering systems which deliver the clean air. This is, however, not good practice and microbiological testing should be carried out routinely during operations as part of clinical audit. Cite this article:
The documentation of deep infection rates in joint replacement is fraught with multiple difficulties. Deep infections acquired in theatre may present late, but some later presenting deep infections are clearly haematogenous, and not related to surgical management. The effect of
Introduction. Operating theatre airflow can be measured using pulsed lasers (particle image velocimetry) but the process is difficult to do in 3D. Cup, vane or hot wire anemometers provide only 2D information. 3D measurements enable better understanding of airflow. Patients/Materials & Methods. We used a Windmaster ultrasound 3D anemometer (Skyview systems), which uses three ultrasound transmitters to measure velocity in XYZ planes, with a sampling rate of 32 Hz. Post processing was done using MATLAB. An operating theatre with an Howorth Exflow canopy was studied. Equipment, including lights, was moved. A 50 cm grid was marked, and measurements were made at intervals up to the ceiling. Door opening was observed within the clean zone and the peripheral zone, next to the door and on the opposite side of the room. Anaesthetic screens were studied during operating. Airflow was visualised initially using video of smoke puffs and subsequently measured using the aeronometer. Results. In the upper part of the ultraclean canopy air velocity was 0.34 m/s with a standard deviation of 0.02 m/s, indicating an almost constant velocity. In the periphery there was more turbulence and horizontal air movement. Door opening had no effect on air movements in the clean zone. In the periphery there was an increase in horizontal airflow when the doors are closed. There is a pattern of upward airflow against an anaesthetic screen. This is unlikely to be caused by warming blankets. If the partial wall of the enclosure is lowered this results in a fast washout of air towards the anaesthetist. Discussion. Traditional anaesthetic screens may interfere with airflow. Door opening is a lesser effect. Conclusion. The 3D anemometer enables detailed mapping of airflow within an
Introduction. Reducing infection in total joint replacement by using
Patient warming significantly decreases the risk
of surgical site infection. Recently there have been concerns that forced
air warming may interfere with unidirectional airflow, potentially
posing an increased risk of infection. Our null hypothesis was that
forced air and radiant warming devices do not increase the temperature
and the number of particles over the surgical site when compared
with no warming device. A forced air warming device was compared with
a radiant warming device and no warming device as a control. The
temperature and number of particles were measured over the surgical
site. The theatre was prepared as for a routine lower-limb arthroplasty
operation, and the same volunteer was used throughout the study. Forced air warming resulted in a significant mean increase in
the temperature (1.1°C
Prior studies have compared the bacterial load observed in laminar flow operating theatres (LFOTs) and standard operating theatres (STOTs) by wound culture and air sampling during surgery. However many organisms responsible for low grade infection after THR are not readily identified on routine culture and may be detectable only by more sensitive techniques such as the poly-merase chain reaction (PCR). This study assessed the wound contamination rate during THRs and compared the results in STOT with that in LFOTs using PCR. We recruited patients undergoing primary THR for osteoarthritis. Surgery was performed in either STOTs or LFOTs, using identical skin preparation solutions, surgical drapes and operating attire. Specimens of the deep tissue, taken at the beginning and end of surgery, were each immediately separated into two sterile containers, one sent for culture (aerobic, anaerobic and enriched meat broth) and the other frozen at minus 80 degrees Celsius for PCR at a later date. In each theatre type, 40 specimens from 20 THRs were analysed by both PCR and culture. Using PCR, bacterial DNA was identified on 12 of 40 specimens (30%) from STOTs, of which 3 were taken at the start of surgery and 9 at the end of the surgery, giving a 45% wound contamination rate (9 of 20). Two specimens (5%), both taken at the end of surgery, were positive on enriched culture. In LFOTs, bacterial DNA was identified by PCR on 8 of 40 specimens (20%), of which 2 were taken at the start of surgery and 6 at the end of surgery, giving a 30% wound contamination rate (6 of 20). No specimens were positive on enriched culture. Wound contamination of primary THR occurs frequently in both STOTs and LFOTs. Although STOTs showed evidence of more frequent wound contamination than LFOTs, with the numbers available, no significant difference was detected. These data remind us the importance of aseptic surgical technique as significant wound contamination can occur despite the use of
Introduction: Although there is evidence that laminar flow operating theatres (LFOTs) can reduce the incidence of wound infection over standard operating theatres (STOTs) when no routine peri-operative antibiotics were used, the evidence for the use with concurrent parenteral antibiotics is less compelling. A number of prior studies have compared the bacterial load observed in LFOTs and STOTs by wound culture and air sampling during surgery. However many organisms responsible for low grade infection after THR are not readily identified on routine culture and may be detectable only by more sensitive techniques such as the polymerase chain reaction (PCR), a molecular biology test for the presence of bacterial DNA. The purpose of this study was to compare the wound contamination rate during THRs performed in STOT with that in LFOTs using PCR. Method: Patients undergoing primary THR for osteoarthritis without a history of joint infection were recruited for the study. Surgery was performed in either STOTs or LFOTs, using identical skin preparation solutions, surgical drapes and operating attire. Specimens of the deep tissue, taken at the beginning and end of surgery, were each immediately separated into two sterile containers, one sent for culture (aerobic, anaerobic and enriched meat broth) and the other frozen at minus 80 degrees Celsius for PCR at a later date. Results: In each theatre type, 40 specimens from 20 THRs were analysed by both PCR and culture (80 specimens and 40 THRs in total). Using PCR, bacterial DNA was identified on 12 of 40 specimens (30%) from STOTs. Of these 12, three were taken at the start of surgery and nine at the end of the surgery, equivalent to a 45% wound contamination rate (9 of 20). Only two specimens (5%), both taken at the end of surgery, were positive on enriched culture. In LFOTs, bacterial DNA was identified by PCR on eight of 40 specimens (20%). Of these eight, two were taken at the start of surgery and six at the end of surgery, equivalent to a 30% wound contamination rate (6 of 20). None of the specimens were positive on enriched culture. Discussions: We concluded that wound contamination of primary THR occurs frequently in both STOTs and LFOTs. Although STOTs showed evidence of more frequent wound contamination than LFOTs, with the numbers available, no significant difference was detected. These data are important in that they confirm that continued vigilance to technique continue to be important as significant wound contamination can occur despite the use of
Patient warming systems are used routinely to prevent hypothermia under anaesthetic, the benefits of which have been clearly shown in the anaesthetic literature. We were concerned that since these systems take ‘dirty’ air from floor level and distribute it over the patient, bacterial counts could be increased. Also, airflow under the blanket itself could disturb the patients’ own skin cells and thereby influence bacterial counts. With slit air sampling we analysed air quality at the simulated operative site by passing a known volume of air over an agar plate (tryptone glucose yeast). Using probability curves we were able to calculate the volume of air required to detect 1 colony forming unit (CFU) per m³ with 97% confidence. All tests were performed in an
