Microbiological commissioning and monitoring of operating theatre suites

Mycological Methods for Routine Air Sampling and Interpretation of Results in Operating Theaters

Many infectious diseases are transmitted via the air and are, therefore, particularly difficult to combat. These infections include various invasive mycoses caused by molds. The usual route of infection is the inhalation of conidia. In hospitals, infection can also occur through the deposition of conidia in otherwise sterile anatomical sites during surgical and other invasive procedures. Therefore, knowledge of airborne mold concentrations can lead to measures to protect patients from fungal infections. The literature on this topic contains insufficient and sometimes ambiguous information. This is evidenced by the fact that there are no international recommendations or guidelines defining the methodology of air sampling and the interpretation of the results obtained. Surgical departments, intensive care units and medical mycology laboratories are, therefore, left to their own devices, leading to significant differences in the implementation of mycological surveillance in hospitals. The aim of this mini-review is to provide an overview of the current methods of air sampling and interpretation of results used in medical mycology laboratories.

Current and potential approaches on assessing airflow and particle dispersion in healthcare facilities: a systematic review

An indoor environment in a hospital building requires a high indoor air quality (IAQ) to overcome patients' risks of getting wound infections without interrupting the recovery process. However, several problems arose in obtaining a satisfactory IAQ, such as poor ventilation design strategies, insufficient air exchange, improper medical equipment placement and high door opening frequency. This paper presents an overview of various methods used for assessing the IAQ in hospital facilities, especially in an operating room, isolation room, anteroom, postoperative room, inpatient room and dentistry room. This review shows that both experimental and numerical methods demonstrated their advantages in the IAQ assessment. It was revealed that both airflow and particle tracking models could result in different particle dispersion predictions. The model selection should depend on the compatibility of the simulated result with the experimental measurement data. The primary and secondary forces affecting the characteristics of particle dispersion were also discussed in detail. The main contributing forces to the trajectory characteristics of a particle could be attributed to the gravitational force and drag force regardless of particle size. Meanwhile, the additional forces could be considered when there involves temperature gradient, intense light source, submicron particle, etc. The particle size concerned in a healthcare facility should be less than 20 μm as this particle size range showed a closer relationship with the virus load and a higher tendency to remain airborne. Also, further research opportunities that reflect a more realistic approach and improvement in the current assessment approach were proposed.

Theatre ventilation

INTRODUCTION

Owing to the COVID-19 pandemic, there has been significant disruption to all surgical specialties. In the UK, units have cancelled elective surgery and a decrease in aerosol generating procedures (AGPs) was favoured. Centres around the world advocate the use of negative pressure environments for AGPs in reducing the spread of infectious airborne particles. We present an overview of operating theatre ventilation systems and the respective evidence with relation to surgical site infection (SSI) and airborne pathogen transmission in light of COVID-19.

METHODS

A literature search was conducted using the PubMed, Cochrane Library and MEDLINE databases. Search terms included "COVID-19", "theatre ventilation", "laminar", "turbulent" and "negative pressure".

FINDINGS

Evidence for laminar flow ventilation in reducing the rate of SSI in orthopaedic surgery is widely documented. There is little evidence to support its use in general surgery. Following previous viral outbreaks, some centres have introduced negative pressure ventilation in an attempt to decrease exposure of airborne pathogens to staff and surrounding areas. This has again been suggested during the COVID-19 pandemic. A limited number of studies show some positive results for the use of negative pressure ventilation systems and reduction in spread of pathogens; however, cost, accessibility and duration of conversion remain an unexplored issue. Overall, there is insufficient evidence to advocate large scale conversion at this time. Nevertheless, it may be useful for each centre to have its own negative pressure room available for AGPs and high risk patients.

The antimicrobial efficacy of shielded ultraviolet germicidal irradiation in CT rooms with intense human circulation

PURPOSE

Computed tomography (CT) premises are one of the strategic points in the spread of hospital-acquired infections. Ultraviolet germicidal irradiation (UVGI) is an effective method that could potentially be used to purify the ambient air in them. However, it cannot be directly used in the presence of humans and, therefore, it is not operationally suitable in such units with continuous human circulation. Newer devices have been developed to purify air with more efficient and shielded UV-C sources. This study aims to assess the microbial air contamination in CT scanning rooms and investigates the efficacy and technical considerations of shielded UV-C arrays.

METHODS

Two shielded UVGI systems, each equipped with 15 Watt UV-C LED arrays, were tested in a very busy CT unit. Initially, a pilot study was performed to determine ambient microorganisms under routine conditions before UVGI installation, followed by three basic scenarios of UVGI use under normal and abnormal conditions: A, UVGI, with both air-conditioning (AC) and ventilation on; B, UVGI, with AC on and ventilation off; C, UVGI, with both AC and ventilation off. Ambient air was sampled in various time points before and after the initialization of UV irradiation and analyzed for colony formation.

RESULTS

The mean total colony count in the pilot study was 1360±450 CFU/m3. Pre-UVGI colony count was 3510 CFU/m3 for Scenario A, ~10000 CFU/m3 for Scenario B and 990 CFU/m3 for Scenario C. Thirty minutes after UVGI, total colony counts in all three scenarios dropped to 30 to 70 CFU/m3. Under normal operating conditions and UVGI, the mean colony count was found as 21.4±13.5 CFU/m3 and the average efficacy of the UVGI was found as 99.39%.

CONCLUSION

This study identified substantial microbial air contamination in CT scanning rooms during normal and abnormal operating conditions. UV-C LED arrays effectively eliminate these microbiological contaminants. This effect is also observed under abnormal operating conditions where no other means of ventilation or air conditioning exists.

Prevention of surgical site infection under different ventilation systems in operating room environment

Biological particles in the operating room (OR) air environment can cause surgical site infections (SSIs). Various ventilation systems have been employed in ORs to ensure an ultraclean environment. However, the effect ofdifferent ventilation systems on the control ofbacteria-carrying particles (BCPs) released from the surgical staff during surgery is unclear. In this study, the performance of four different ventilation systems (vertical laminar airflow ventilation (VLAF), horizontal laminar airflow ventilation (HLAF), differential vertical airflow ventilation (DVAF), and temperature-controlled airflow ventilation (TAF)) used in an OR was evaluated and compared based on the spatial BCP concentration. The airflow field in the OR was solved by the Renormalization Group (RNG) k-ε turbulence model, and the BCP phase was calculated by Lagrangian particle tracking (LPT) and the discrete random walk (DRW) model. It was found that the TAF system was the most effective ventilation system among the four ventilation systems for ensuring air cleanliness in the operating area. This study also indicated that air cleanliness in the operating area depended not only on the airflow rate of the ventilation system but also on the airflow distribution, which was greatly affected by obstacles such as surgical lamps and surgical staff.

Genetic relationship between bacteria isolated from intraoperative air samples and surgical site infections at a major teaching hospital in Ghana

BACKGROUND

In low- and middle-income countries (LMICs) the rate of surgical site infections (SSI) is high, leading to negative patient outcomes and excess healthcare costs. A causal relationship between airborne bacteria in the operating room and SSI has not been established, at a molecular or genetic level. We studied the relationship between intraoperative airborne bacteria and bacteria causing SSI in an LMIC.

METHODS

Active air sampling using a portable impactor was performed during clean or clean-contaminated elective surgical procedures. Active patient follow-up consisting of phone calls and clinical examinations was performed 3, 14 and 30 days after surgery. Bacterial isolates recovered from SSI and air samples were compared by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) identification, ribotyping, whole genome sequencing (WGS), and metagenomic analysis.

RESULTS

Of 128 included patients, 116 (91%) completed follow-up and 11 (9%) developed SSI. Known pathogenic bacteria were isolated from intraoperative air samples in all cases with SSI. A match between air and SSI isolates was found by MALDI-TOF in eight cases. Matching ribotypes were found in six cases and in one case both WGS and metagenomic analysis showed identity between air- and SSI-isolates.

CONCLUSION

The study showed high levels of intraoperative airborne bacteria, an SSI-rate of 9% and a genetic link between intraoperative airborne bacteria and bacteria isolated from SSIs. This indicates the need for awareness of intraoperative air quality in LMICs.

An exploration on the relationship between traffic flow and the rate of surgical site infections: A literature review

Surgical site infections are the second most frequent type of health-care associated infections in Europe and America. Public Health England's data on 139,691 operations at 209 hospitals reported 1,635 surgical site infections between April 2012 and March 2017. Patients with a surgical site infection are twice as likely to die, five times more likely to be readmitted after discharge and are likely to have a prolonged hospitalization. Therefore, it is still a significant issue that professionals need to help reduce. This literature review looks at ventilation within theatres and how traffic flow can affect the air flow and if it can increase the incidence rates of surgical site infections. Recommendations of strategies are made to help reduce traffic flow within operating theatres.

Concentration and type of bioaerosols before and after conventional disinfection and sterilization procedures inside hospital operating rooms

Operating rooms (ORs) in hospitals are sensitive wards because patients can get infections. This work aimed to characterize the type and concentration of bioaerosols in nine ORs of an educational hospital before and after sterilization and disinfection. During 2017, fungal samples were incubated at 25-28 °C for 3-7 days and bacterial samples at 37 °C for 24-48 h. The study results showed that the concentrations of fungi before cleaning procedures (for both of disinfection and sterilization) were limited from 4.83 to 18.40 CFU/m3 and after cleaning procedures ranged from 1.90 to 8.90 CFU/m3. In addition, the concentrations of bacteria before cleaning procedures were limited 14.65-167.40 CFU/m3 and after cleaning procedures ranged from 9.50 to 38.40 CFU/m3. The difference between the mean concentrations of airborne bioaerosols before and after sterilization was significantly different than the suggested value of 30 CFU/m3 (p ≤ 0.05). The bacterial concentration was higher than the recommended value (30 CFU/m3) in 41% of the ORs. The main fungal species identified in the indoor air of ORs (before vs. after sterilization) were A. fumigatus (25.6 vs. 18.3%), A. Niger (11.6 vs. 5.8%), Penicillium spp. (5.5 vs. 3.3%), Alternaria spp. (2.8 vs. 0.7%), Fusarium spp. (9.7 vs. 3.7%), Mucor spp. (15 vs. 12.7%), Cephalotrichum spp. (1.7 vs. 0.8%), A. Flavus (24.6 vs. 18.5%), Cladosporium spp. (2.6 vs. 0.8%), and Trichoderma spp. (0 vs. 0.9%). The growth of biological species even after sterilization and disinfection likely resulted from factors including poor ventilation, sweeping of OR floors, inadequate HVAC filtration, high humidity, and also lack of optimum management of infectious waste after surgery. Designing well-constructed ventilation and air-conditioning systems, replacing HEPA filters, implementing more stringent, frequent, and comprehensive disinfection procedures, and controlling temperature and humidity can help decrease bioaerosols in ORs.

A Clinical Test to Measure Airborne Microbial Contamination on the Sterile Field During Total Joint Replacement: Method, Reference Values, and Pilot Study

Background

Airborne microbe-carrying particles in the operating-room environment during total joint replacement are a risk factor for periprosthetic joint infection. The present study focuses on a simple environmental test, based on practices used in aseptic cleanrooms, to quantify the deposition of microbe-carrying particles onto the sterile field.

Methods

Settle plates are exposed Petri dishes. A settle plate test system and sampling plan were developed from current practices used in aseptic manufacturing. A pilot study evaluated this system in an orthopaedic operating room during 22 total knee and hip arthroplasties. The microbial deposition total (MDT), expressed in colonies/m², is proposed as an outcome variable to report airborne sterile-field contamination as measured with settle plates. Two reference MDT levels were developed: (1) an upper limit of 450, corresponding with the ultraclean air definition of 10 colonies/m³, and (2) a target level of 100, corresponding with 1 colony/m³. These levels also correspond with widely used limits in aseptic cleanrooms and controlled environments.

Results

High MDT standard deviations were noted. Ninety-one percent (95% confidence interval, 71.0% to 98.7%) of wound zone MDT levels were within the upper limit. Twenty-seven percent (95% confidence interval, 12.9% to 48.4%) of wound zone levels were within the target level.

Conclusions

Settle plates are a feasible technique to test environmental levels of microbe-carrying particles on sterile fields during total joint replacement for scientific and environmental quality studies.

Clinical Relevance

This settle plate operating-room environmental test can be used in future research to validate the presence of actual ultraclean-air conditions during periprosthetic joint infection outcome studies. Surgeons also can use this test to measure intraoperative airborne microbe-carrying-particle sterile-field contamination and compare it with ultraclean-air reference levels for environmental quality-control programs.

A cost-effectiveness modelling study of strategies to reduce risk of infection following primary hip replacement based on a systematic review

BACKGROUND

A deep infection of the surgical site is reported in 0.7% of all cases of total hip arthroplasty (THA). This often leads to revision surgery that is invasive, painful and costly. A range of strategies is employed in NHS hospitals to reduce risk, yet no economic analysis has been undertaken to compare the value for money of competing prevention strategies.

OBJECTIVES

To compare the costs and health benefits of strategies that reduce the risk of deep infection following THA in NHS hospitals. To make recommendations to decision-makers about the cost-effectiveness of the alternatives.

DESIGN

The study comprised a systematic review and cost-effectiveness decision analysis.

SETTING

77,321 patients who had a primary hip arthroplasty in NHS hospitals in 2012.

INTERVENTIONS

Nine different treatment strategies including antibiotic prophylaxis, antibiotic-impregnated cement and ventilation systems used in the operating theatre.

MAIN OUTCOME MEASURES

Change in the number of deep infections, change in the total costs and change in the total health benefits in quality-adjusted life-years (QALYs).

DATA SOURCES

Literature searches using MEDLINE, EMBASE, Cumulative Index to Nursing and Allied Health Literature and the Cochrane Central Register of Controlled Trials were undertaken to cover the period 1966-2012 to identify infection prevention strategies. Relevant journals, conference proceedings and bibliographies of retrieved papers were hand-searched. Orthopaedic surgeons and infection prevention experts were also consulted.

REVIEW METHODS

English-language papers only. The selection of evidence was by two independent reviewers. Studies were included if they were interventions that reported THA-related deep surgical site infection (SSI) as an outcome. Mixed-treatment comparisons were made to produce estimates of the relative effects of competing infection control strategies.

RESULTS

Twelve studies, six randomised controlled trials and six observational studies, involving 123,788 total hip replacements (THRs) and nine infection control strategies, were identified. The quality of the evidence was judged against four categories developed by the National Institute for Health and Care Excellence Methods for Development of NICE Public Health Guidance ( http://publications.nice.org.uk/methods-for-the-development-of-nice-public-health-guidance-third-edition-pmg4 ), accessed March 2012. All evidence was found to fit the two highest categories of 1 and 2. Nine competing infection control interventions [treatments (Ts) 1-9] were used in a cohort simulation model of 77,321 patients who had a primary THR in 2012. Predictions were made for cases of deep infection and total costs, and QALY outcomes. Compared with a baseline of T1 (no systemic antibiotics, plain cement and conventional ventilation) all other treatment strategies reduced risk. T6 was the most effective (systemic antibiotics, antibiotic-impregnated cement and conventional ventilation) and prevented a further 1481 cases of deep infection, and led to the largest annual cost savings and the greatest gains to QALYs. The additional uses of laminar airflow and body exhaust suits indicate higher costs and worse health outcomes.

CONCLUSIONS

T6 is an optimal strategy for reducing the risk of SSI following THA. The other strategies that are commonly used among NHS hospitals lead to higher cost and worse QALY outcomes. Policy-makers, therefore, have an opportunity to save resources and improve health outcomes. The effects of laminar air flow and body exhaust suits might be further studied if policy-makers are to consider disinvesting in these technologies.

LIMITATIONS

A wide range of evidence sources was synthesised and there is large uncertainty in the conclusions.

FUNDING

The National Institute for Health Research Health Technology Assessment programme and the Queensland Health Quality Improvement and Enhancement Programme (grant number 2008001769).

Traffic flow and microbial air contamination in operating rooms at a major teaching hospital in Ghana

BACKGROUND

Current literature examining the relationship between door-opening rate, number of people present, and microbial air contamination in the operating room is limited. Studies are especially needed from low- and middle-income countries, where the risk of surgical site infections is high.

AIM

To assess microbial air contamination in operating rooms at a Ghanaian teaching hospital and the association with door-openings and number of people present. Moreover, we aimed to document reasons for door-opening.

METHODS

We conducted active air-sampling using an MAS 100^® portable impactor during 124 clean or clean-contaminated elective surgical procedures. The number of people present, door-opening rate and the reasons for each door-opening were recorded by direct observation using pretested structured observation forms.

FINDINGS

During surgery, the mean number of colony-forming units (cfu) was 328 cfu/m³ air, and 429 (84%) of 510 samples exceeded a recommended level of 180 cfu/m³. Of 6717 door-openings recorded, 77% were considered unnecessary. Levels of cfu/m³ were strongly correlated with the number of people present (P = 0.001) and with the number of door-openings/h (P = 0.02). In empty operating rooms, the mean cfu count was 39 cfu/m³ after 1 h of uninterrupted ventilation and 52 (51%) of 102 samples exceeded a recommended level of 35 cfu/m³.

CONCLUSION

The study revealed high values of intraoperative airborne cfu exceeding recommended levels. Minimizing the number of door-openings and people present during surgery could be an effective strategy to reduce microbial air contamination in low- and middle-income settings.

Effect of switching off unidirectional downflow systems of operating theaters during prolonged inactivity on the period before the operating theater can safely be used

BACKGROUND

Switching off air handling systems in operating theaters during periods of prolonged inactivity (eg, nights, weekends) can produce a substantial reduction of energy expenditure. However, little evidence is available regarding the effect of switching off the air handling system during periods of prolonged inactivity on the air quality in operating theaters during operational periods. The aim of this study is to determine the amount of time needed after restarting the ventilation system to return to a stable situation, with air quality at least equal to the situation before switching off the system.

METHODS

Measurements were performed in 3 operating theaters, all of them equipped with a unidirectional downflow (UDF) system. Measurements (particle counts of emitted particles with a particle size ≥0.5 µm) were taken during the start-up of the ventilation system to determine when prespecified degrees of protection were achieved. Temperature readings were taken to determine when a stable temperature difference between the periphery and the protected area was reached, signifying achievement of a stable condition.

RESULTS

After starting up the system, the protected area achieved the required degrees of protection within 20 minutes (95% upper confidence limit). A stable temperature difference was achieved within 23 minutes (95% upper confidence limit). Both findings lie well within the period of 25 minutes normally required for preparations before the start of surgical procedures.

CONCLUSIONS

Switching off the ventilation system during prolonged inactivity (during the night and weekend) has no negative effect on the air quality in UDF operating theaters during normal operational hours.

Does laminar flow ventilation reduce the rate of infection?

Aims

To determine whether there is any difference in infection rate at 90 days between trauma operations performed in laminar flow and plenum ventilation, and whether infection risk is altered following the installation of laminar flow (LF).

Patients and Methods

We assessed the impact of plenum ventilation (PV) and LF on the rate of infection for patients undergoing orthopaedic trauma operations. All NHS hospitals in England with a trauma theatre(s) were contacted to identify the ventilation system which was used between April 2008 and March 2013 in the following categories: always LF, never LF, installed LF during study period (subdivided: before, during and after installation) and unknown. For each operation, age, gender, comorbidity, socio-economic deprivation, number of previous trauma operations and surgical site infection within 90 days (SSI90) were extracted from England’s national hospital administrative Hospital Episode Statistics database. Crude and adjusted odds ratios (OR) were used to compare ventilation groups using hierarchical logistic regression. Subanalysis was performed for hip hemiarthroplasties.

Results

A total of 803 065 trauma operations were performed during this time; 19 hospitals installed LF, 124 already had LF, 13 had PV and the type of ventilation was unknown in 28. Patient characteristics were similar between the groups. The rate of SSI90 was similar for always LF and PV (2.7% and 2.4%). For hemiarthroplasties of the hip, the rates of SSI90 were significantly higher for LF compared with PV (3.8% and 2.6%, OR 1.45, p = 0·001). Hospitals installing LF did not see any statistically significant change in the rate of SSI90.

Conclusion

The results of this observational study imply that infection rate is similar when orthopaedic trauma surgery is performed in LF and PV, and is unchanged by installing LF in a previously PV theatre. Cite this article: Bone Joint J 2016;98-B:1262–9.

The OneTogether collaborative approach to reduce the risk of surgical site infection: identifying the challenges to assuring best practice

BACKGROUND

Surgical site infections (SSI) account for 16% of healthcare associated infections, and are associated with considerable morbidity, mortality and increased costs of care. Ensuring evidence-based practice to prevent SSI is incorporated across the patient's surgical journey is complex. OneTogether is a quality improvement collaborative of infection prevention and operating department specialists, formed to support the spread and adoption of best practice to prevent SSI. This paper describes the findings of an expert workshop on infection prevention in operating departments.

METHODS

A total of 84 delegates from 75 hospitals attended the workshop, comprising 46 (55%) theatre nurses/operating department practitioners; 16 (19%) infection control practitioners and 22 (26%) other healthcare practitioners. Discussion focused on evidence, policy implementation and barriers to best practice. Responses were synthesised into a narrative review.

RESULTS

Delegates reported significant problems in translating evidence-based guidance into everyday practice, lack of local polices and poor compliance. Major barriers were lack of leadership, poorly defined responsibilities, and lack of knowledge/training.

CONCLUSIONS

This workshop has provided important insights into major challenges in assuring compliance with best practice in relation to the prevention of SSI. The OneTogether partnership aims to support healthcare practitioners to improve the outcomes of patients undergoing surgery by reducing the risk of SSI.

Real-time measurements of airborne biologic particles using fluorescent particle counter to evaluate microbial contamination: results of a comparative study in an operating theater

BACKGROUND

Airborne bacterial contamination poses a risk for surgical site infection, and routine surveillance of airborne bacteria is important. Traditional methods for detecting airborne bacteria are time consuming and strenuous. Measurement of biologic particle concentrations using a fluorescent particle counter is a novel method for evaluating air quality. The current study was to determine whether the number of biologic particles detected by the fluorescent particle counter can be used to indicate airborne bacterial counts in operating rooms.

METHODS

The study was performed in an operating theater at a university hospital in Hefei, China. The number of airborne biologic particles every minute was quantified using a fluorescent particle counter. Microbiologic air sampling was performed every 30 minutes using an Andersen air sampler (Pusong Electronic Instruments, Changzhou, China). Correlations between the 2 different methods were analyzed by Pearson correlation coefficients.

RESULTS

A significant correlation was observed between biologic particle and bacterial counts (Pearson correlation coefficient = 0.76), and the counting results from 2 methods both increased substantially between operations, corresponding with human movements in the operating room.

CONCLUSION

Fluorescent particle counters show potential as important tools for monitoring bacterial contamination in operating theatres.

Microbial isolations from maxillofacial operation theatre and its correlation to fumigation in a teaching hospital in India

Postoperative infection and sepsis remain a major cause of morbidity among patients undergoing surgery. Maintenance of strict asepsis is essential if post-operative infection and its consequences are to be minimized. In developing countries maintenance of asepsis in most operation theatres is limited to fumigation and mopping. Clinical trials have confirmed that 80-90 % of bacterial contaminants found in wound after surgery come from microbes present in air of operating theatre. A study was conducted to evaluate the microbiological contamination of maxillofacial operation theatres in India and its correlation to weekly fumigation. A total of 6,723 culture plates, including 2,241 air and 4,482 swab samples were studied. Samples were collected at prefumigation, midcycle and post-fumigation stages and were cultured over three different medias. Predominant bacteria identified were Staphylococcus aureus (76 out of 83 samples by active air sampling) followed by Streptococcus while Aspergillus was the main fungal isolate. Formaldehyde based fumigation decreased the colony forming units (cfu/m(3)) of all organisms in different samples and was found to be highly effective against Fungi and E. coli. Literature suggests that for conventional operating theatres the bioload should not exceed 35 cfu/m(3) in an empty theatre. In our study the cfu levels were always lower immediately after fumigation was carried out; however they moved up beyond this limit as the days passed. This implies that once a week fumigation with formaldehyde is less than optimal to achieve acceptable levels of disinfection.

Real-time monitoring of non-viable airborne particles correlates with airborne colonies and represents an acceptable surrogate for daily assessment of cell-processing cleanroom performance

BACKGROUND AIMS

Airborne particulate monitoring is mandated as a component of good manufacturing practice. We present a procedure developed to monitor and interpret airborne particulates in an International Organization for Standardization (ISO) class 7 cleanroom used for the cell processing of Section 351 and Section 361 products.

METHODS

We collected paired viable and non-viable airborne particle data over a period of 1 year in locations chosen to provide a range of air quality. We used receiver operator characteristic (ROC) analysis to determine empirically the relationship between non-viable and viable airborne particle counts.

RESULTS

Viable and non-viable particles were well-correlated (r(2) = 0.78), with outlier observations at the low end of the scale (non-viable particles without detectable airborne colonies). ROC analysis predicted viable counts ≥ 0.5/feet(3) (a limit set by the United States Pharmacopeia) at an action limit of ≥ 32 000 particles (≥ 0.5 µ)/feet(3), with 95.6% sensitivity and 50% specificity. This limit was exceeded 2.6 times during 18 months of retrospective daily cleanroom data (an expected false alarm rate of 1.3 times/year). After implementing this action limit, we were alerted in real time to an air-handling failure undetected by our hospital facilities management.

CONCLUSIONS

A rational action limit for non-viable particles was determined based on the correlation with airborne colonies. Reaching or exceeding the action limit of 32 000 non-viable particles/feet(3) triggers suspension of cleanroom cell-processing activities, deep cleaning, investigation of air handling, and a deviation management process. Our full procedure for particle monitoring is available as an online supplement.

Microbial air monitoring in operating theatres: experience at the University Hospital of Parma

BACKGROUND

Microbial air monitoring in operating theatres has been a subject of interest and debate. No generally accepted sampling methods and threshold values are available.

AIM

To assess microbial air contamination in empty and working conventionally ventilated operating theatres over a three-year period at the University Hospital of Parma, Italy.

METHODS

Air sampling was performed in 29 operating theatres. Both active and passive sampling methods were used to assess bacterial and fungal contamination.

FINDINGS

In empty theatres, median bacterial values of 12 colony-forming units (cfu)/m(3) [interquartile range (IQR) 4-32] and 1 index of microbial air contamination (IMA) (IQR 0-3) were recorded. In working theatres, these values increased significantly (P < 0.001) to 80 cfu/m(3) (IQR 42-176) and 7 IMA (IQR 4-13). Maximum recorded values were 166 cfu/m(3) and 8 IMA for empty theatres, and 798 cfu/m(3) and 42 IMA for working theatres. Combining active and passive samplings, fungi were isolated in 39.13% of samples collected in empty theatres and 56.95% of samples collected in working theatres. Over the three-year study period, bacterial contamination decreased in both empty and working theatres, and the percentage of samples devoid of fungi increased. In working theatres, a significant correlation was found between the bacterial contamination values assessed using passive and active sampling methods (P < 0.001).

CONCLUSION

Microbiological monitoring is a useful tool for assessment of the contamination of operating theatres in order to improve air quality.

Forced-air warming: a source of airborne contamination in the operating room?

Forced-air-warming (FAW) is an effective and widely used means for maintaining surgical normothermia, but FAW also has the potential to generate and mobilize airborne contamination in the operating room.

We measured the emission of viable and non-viable forms of airborne contamination from an arbitrary selection of FAW blowers (n=25) in the operating room. A laser particle counter measured particulate concentrations of the air near the intake filter and in the distal hose airstream. Filtration efficiency was calculated as the reduction in particulate concentration in the distal hose airstream relative to that of the intake. Microbial colonization of the FAW blower's internal hose surfaces was assessed by culturing the microorganisms recovered through swabbing (n=17) and rinsing (n=9) techniques.

Particle counting revealed that 24% of FAW blowers were emitting significant levels of internally generated airborne contamination in the 0.5 to 5.0 µm size range, evidenced by a steep decrease in FAW blower filtration efficiency for particles 0.5 to 5.0 µm in size. The particle size-range-specific reduction in efficiency could not be explained by the filtration properties of the intake filter. Instead, the reduction was found to be caused by size-range-specific particle generation within the FAW blowers. Microorganisms were detected on the internal air path surfaces of 94% of FAW blowers.

The design of FAW blowers was found to be questionable for preventing the build-up of internal contamination and the emission of airborne contamination into the operating room. Although we did not evaluate the link between FAW and surgical site infection rates, a significant percentage of FAW blowers with positive microbial cultures were emitting internally generated airborne contamination within the size range of free floating bacteria and fungi (<4 µm) that could, conceivably, settle onto the surgical site.

Guidelines for the control and prevention of meticillin-resistant Staphylococcus aureus (MRSA) in healthcare facilities

Meticillin-resistant Staphylococcus aureus (MRSA) remains endemic in many UK hospitals. Specific guidelines for control and prevention are justified because MRSA causes serious illness and results in significant additional healthcare costs. Guidelines were drafted by a multi-disciplinary group and these have been finalised following extensive consultation. The recommendations have been graded according to the strength of evidence. Surveillance of MRSA should be undertaken in a systematic way and should be fed back routinely to healthcare staff. The inappropriate or unnecessary use of antibiotics should be avoided, and this will also reduce the likelihood of the emergence and spread of strains with reduced susceptibility to glycopeptides, i.e. vancomycin-intermediate S. aureus/glycopeptide-intermediate S. aureus (VISA/GISA) and vancomycin-resistant S. aureus (VRSA). Screening for MRSA carriage in selected patients and clinical areas should be performed according to locally agreed criteria based upon assessment of the risks and consequences of transmission and infection. Nasal and skin decolonization should be considered in certain categories of patients. The general principles of infection control should be adopted for patients with MRSA, including patient isolation and the appropriate cleaning and decontamination of clinical areas. Inadequate staffing, especially amongst nurses, contributes to the increased prevalence of MRSA. Laboratories should notify the relevant national authorities if VISA/GISA or VRSA isolates are identified.

Survey of operating theatre ventilation facilities for minimally invasive surgery in Great Britain and Northern Ireland: current practice and considerations for the future

Increasing use of minimally invasive surgery (MIS) and other invasive procedures has raised the question of what ventilation facilities are appropriate for such procedures to prevent infection. The Hospital Infection Society (HIS) Working Party on Infection Control in Operating Theatres undertook a survey of practice in Great Britain and Northern Ireland on the ventilation facilities provided for a variety of MIS and other procedures. Five hundred and fifty questionnaires were forwarded to HIS members, and 186 (39%) replies were received. Fifty-eight percent were from district general hospitals (DGHs). Designated theatres for orthopaedic surgery (although not necessarily ultraclean ventilated theatres) were available in more than 80% of hospitals, with approximately 50% of hospitals having designated theatres for a variety of other surgical subspecialities. Approximately two-thirds of urological procedures were performed in conventionally ventilated operating theatres. Most radiological procedures were performed in non-ventilated theatres or treatment rooms. In around half of the DGHs and university/referral hospitals, orthopaedic MIS procedures such as arthroscopy were performed in ultraclean ventilated theatres. This survey revealed considerable variation in the use of conventionally ventilated theatres and ultraclean ventilated theatres. In particular, many radiological and anaesthetic procedures are performed in treatment rooms or ventilated rooms with less than 20 air changes per hour. Whilst it is not clear whether this is acceptable practice given current knowledge, large-scale clinical trials to determine what standards of ventilation are appropriate to minimize infection for these types of procedures would be difficult to conduct. Research is needed on the relative risk of airborne infection for a variety of procedures, including whether all prosthetic implant procedures should be carried out in ultraclean ventilated theatres, as infection associated with implants is often of airborne origin and of considerable clinical significance.

Fungal contamination of air conditioning units in operating theatres in India

Postoperative fungal infections may be caused by discharge of spores from contaminated air conditioning (AC) units. The filters of such units may act as a nidus for the growth of fungi. In this survey, filters of AC units in 25 operating theatres in India were evaluated quarterly over two years. The overall rate of fungal colonization of the AC filters was 26%. In addition, window-mounted AC units had higher fungal counts than wall-mounted AC units. We conclude that although the exact load of fungal spores necessary to initiate infections is unknown, AC units in operating theatres should be meticulously maintained and frequently monitored to minimize the chances of growth and proliferation of potentially pathogenic fungi. Data from this study also suggest that the design of the AC unit may play an important role in reducing fungal spore counts in the air of operating theatres in developing countries.

Ventilation performance in the operating theatre against airborne infection: numerical study on an ultra-clean system

A laminar airflow study was performed in a standard operating theatre in Hong Kong, the design of which followed the requirements of the UK Health Technical Memorandum. The study of the ultra-clean ventilation system investigated the effectiveness of the laminar flow in: (i) preventing bioaerosols released by the surgical staff from causing postoperative infection of the patient; and (ii) protecting the surgical team against infection by bacteria from the wound site. Seven cases of computer simulation are presented and the sensitivity of individual cases is discussed. Air velocity at the supply diffuser has been identified as one of the most important factors in governing the dispersion of airborne infectious particles. Higher velocity within the laminar regime is advantageous in minimizing the heat-dissipation effect, and to ensure an adequate washing effect against particulate settlement. Inappropriate positioning of the medical lamps can be detrimental. Omission of a partial wall may increase the infection risk of the surgical team due to the ingression of room air at the supply diffuser periphery. This paper stresses that a successful outcome in preventing airborne infection depends as much on resolving human factors as on overcoming technical obstacles.

Ventilation performance in operating theatres against airborne infection: review of research activities and practical guidance

Surgical site infection risk due to airborne bacteria is a key area of consideration in developing operating theatre ventilation design and monitoring procedures. This paper reviews the recent extensive research into operating theatre ventilation development in relation to the design concepts in operating theatre layout, pressurization and ventilation, particularly the evolvement of ultra-clean ventilation. The findings that led to the current technical standards and the developments of microbial measurements and numerical techniques are discussed. Since the late 1980s, computational fluid dynamics has been a fast developing tool used in the prediction of room air distribution and contaminant dispersion. The basic principles and current practice applying to operating theatre ventilation studies are introduced.

Shutting down operating theater ventilation when the theater is not in use: infection control and environmental aspects

OBJECTIVE

In hospital operating rooms (ORs), specially conditioned air is supplied to protect patients from airborne agents that may cause infections. This study investigated whether it is hygienically safe to shut down the air supply at night if measures are taken to ensure a timely restart before surgery is performed.

DESIGN

Experimental study.

SETTING

Neurosurgical OR of a German university hospital.

METHODS

The ventilation system was switched off and restarted after 10 hours. Particles suspended in the air near the operating table were counted, OR temperature was measured, and settle plates were exposed and incubated.

RESULTS

In 13 investigations, a median of 1.3 x 10(4) particles 0.5 microm/m3 or greater (range, 5.8 x 10(3) to 1.1 x 10(5)) were documented immediately after restart in the morning. After 10 minutes and subsequently, no test showed a particle count exceeding the threshold limit of 1.0 x 10(4) particles 0.5 microm/m3 or greater recommended by the German Society of Hygiene and Microbiology. Only a few colony-forming units (CFU) were detected per settle plate (median, 0 CFU/60 cm2; range, 0 to 8) and OR temperatures quickly reached normal levels.

CONCLUSIONS

Shutting down OR ventilation during off-duty periods does not appear to result in an unacceptably high particle count or microbial contamination of the OR air shortly after the system is restarted. Because substantial energy and cost savings are likely, this should be considered in hygienically safe heating, ventilation, and air conditioning systems. However, normal ventilation should be established at least 30 minutes before surgical activity.

A UK historical perspective on operating theatre ventilation

As part of the preparation for the report of the Hospital Infection Society Working Party on Infection Control and Operating Theatres, studies published from the UK on the subject of operating theatre ventilation were reviewed. Few have convincingly demonstrated a direct relationship between the microbiological quality of operating theatre air and postoperative wound infection. Nevertheless, the findings from these studies have had a major influence on the development of official UK guidance on the design, performance and testing of ventilation in both conventional and ultraclean operating theatres.