Laminar Air-flow to Control Operating Room Infection

INTRODUCTION

Surgical site infections (SSIs) are defined as infections occurring within 30 days after surgical operation or within one year if an implant is left in place and affecting either the incision or deep tissue at the operation site (Owens and Stoessel 2008). SSIs are reported as the major cause of high morbidity and mortality among post -operative patients (Weigelt et.al. 2010). According to UK National Joint Registry Report, during 2003 -2006 period infection was responsible for about 19 % failure of joint surgery resulting in revision procedures (Sandiford and skinner 2009).

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Micro-organisms in the air particles settle on the wound, dressings and surgical instruments and cause infections (Chow and Yang 2005). Whyte et.al (1982) identified that contamination from patient’s skin as the cause of infection in 2% cases and from theatre personnel in 98% cases. They also found that in 30% cases, contaminants reach the wound from theatre personnel via air and in 70% cases it is via hands.

Generally air quality in the operating room is maintained ventilation system. Additional improvements can be achieved by laminar air-flow system or UV lights. Laminar air-flow system is expensive and require continues maintenance. Its installation increases building cost and the operational cost (Cacciariet.al., 2004: Hansen, 2005). Studies conducted to evaluate the effectiveness of laminar flow produced mixed results and there is no consensus on its role in infection control (Sandiford 2007). In this setting, this paper reviews the recent studies to examine the effectiveness of laminar air-flow in reducing SSIs.

Studies for this review were found by searching on databases such as CINAHL, PubMed, Science Direct, Ovidsp, Science Citation Index (ISI) and Google scholar. Keywords used for this search are “laminar air flow”, “surgical site infection”, “operating room air quality”, “airborne infections + operating theatre”, “LMA + infection control”. As laminar air-flow is used mainly in orthopaedic theatres, majority of the studies are on joint surgery.

OPERATING THEATRE AIR QUALITY AND INFECTION CONTROL

Indoor air in an operating theatre contains dust which consists of substances released from disinfectant and sterilizers, respiratory droplets, insect parts smoke released from cautry. Dust particles act as a carrier for transporting microorganisms laden particles and can settle on surgical wound and there by cause infection (Neil 2005). Air particles are found to be responsible for about 80% – 90% of microbial contamination (CDC 2005).

Modern operating theatres are generally equipped with conventional ventilation system in which filters can remove airborne particles of size >5mm about 80-95% (Dharan 2002). The efficacy of operating room ventilation is measured by the colony forming units (CFU) of organisms present per cubic meter. The conventional ventilation (Plenum) with 20 air exchanges is considered efficient if it achieves the colony count of 35cfu/m3 or less (Bannister 2002).

Ventilation system with laminar air-flow directs the air-flow in one direction and sweeps the air particle over the wound site to the exits (CDC 2003). Laminar air-flow with HEPA (High Efficiency Particulate Arrestment) filters system has the capacity to remove air particles of size 0.3 µm up to 99.9 % and can produce 300 air exchanges per hour in ultraclean orthopaedic theatres. (Sandiford and skinner 2009).

Laminar air-flow units are generally two types; ceiling-mounted (vertical flow) or wall-mounted (horizontal flow). There are inconveniences associated with both types. Generally the major problem associated with laminar air-flow is flow disruption. With vertical laminar flow, it is the heat generated by surgical lamps creates air turbulence while with horizontal laminar flow it is the surgical team that disrupt the air-flow (Dharan 2002).

LAMINAR AIR FLOW IN INFECTION CONTROLL

Laminar air-flow system is mainly used in implant surgeries where even a small number of microorganisms can cause infection. In joint replacement surgeries, one of the main causes of early (within 3 months) and delayed (within 18 months to 2 years) deep prosthetic infections was found colonisation during surgery (Knobben 2006). Laminar air flow is supposed to minimize contamination by mobilizing uniform and large volume of clean air to the surgical area and Contaminants are flushed out instantly (Chow and Yang, 2004). Some studies found that this method is effective in reducing infection but some others produced contradicting results (give some reference)

A recent study conducted by Kakwani et.al. (2007) found that laminar air-flow system is effective in reducing the reoperation rate in Austin-Moore hemiarthroplasty. Their study compared the reoperation rate between theatres with laminar air-flow and theatres without laminar air-flow system. A cohort of 435 patients who had Austin-Moore hemiarthroplasties at Good Hope Hospital in Birmingham between August 2000 and July 2004 were selected for this study. Of those 435 patients, 212 had operation in laminar air-flow theatres and 223 had operation in non-laminar air-flow theatres. Data were collected by reviewing case notes and radiographs. For all cases antibiotics were administrated and water impervious surgical gowns and drapes were used. In the non-laminar air-flow group it was found that the re-operation rate for all indication in the first year after hemiarthroplasties was 5.8 % (13/223), while in the laminar air-flow group it was 1.4% (3/212). Analysis found that there were no statistically significant relation between re-operation rate and water impervious gown and drapes (p=0.15), while use of laminar air-flow found a statistically significant drop (p=0.0285) in re-operation rate within the first year after hemiarthroplasties. They found that re-operation rate in no-laminar air-flow theatres were four times greater than that in laminar airflow theatres.

Even though the aim of the study was clearly described there was no review of existing studies to identify the gap in the research. Study methods and details of statistical analysis were given elaborately. The sample size seems sufficient. Results were summarized and presented using graphs and charts. Discussion of results was short and seems not adequate to address the objectives of the study. There was no attempt to explain the casual relationship. For example researches were making statements such as “…the introduction of water-impervious drapes and gowns did not seem to make a statistically significant improvement in the result….” (p.823). Researchers failed to acknowledge any limitations of the study. Data for this study was collected by reviewing patients’ records. Patients records are considers as confidential and researchers didn’t mention whether they received consent from the patients or ethical approval form institution to conduct the study. This can be considered as an ethical flaw of this study.

There are studies which found that laminar air-flow system is not effective in reducing infection rate. In their study Brandt C et.al (2008) found that infection rate was substantially high in theatres with laminar air-flow system. This was a retrospective cohort-study based on routine surveillance data from German national nosocomial infections surveillance system (KISS). Hospitals which had performed at least 100 operations between the years 2000 and 2004 were selected for this study. Type of ventilation technology installed in operation rooms of selected hospitals were collected separately through questionnaire from infection control teams in the participating hospitals. Surgical departments were grouped into categories according to the type of ventilation system installed. Departments using artificial operating room (OR) ventilation with either turbulent or laminar airflow was included in this study.

Total 63 surgical departments from 55 hospitals were included in this study. Analysis was performed to the data set created by merging the questionnaire data on OR ventilation and surveillance data from the KISS data base. The data set analysed contained 99230 operations with 1901 SSIs. Age and gender of the patient was found a significant risk factor of SSI in most procedures. Univariate analysis conducted found that rate of SSIs was high in departments with laminar air flow ventilation. Multivariate analysis also confirmed this finding. Authors argue that it may be due to the improper positioning theatre personnel in horizontal laminar flow room.

Researches provided a well-researched literature review which clearly identified gap in current research. Objectives and design of the study was properly explained. Study was based on a large sample size. Results were discussed in detail and casual relations were well explained. Enough tables were used to present results. Limitations were properly discussed.

Knobben et.al (2006) conducted an experimental study to evaluate how systemic changes together with behavioural changes can decreases intra-operative contamination. This study was conducted in the university Medical Centre Groningen, The Netherlands. A random sample of 207 surgical procedures which involved total knee or hip prosthesis from July 2001 to January 2004 was selected for this study. Two sequential series of behavioural and systemic changes were introduced to ascertain their role in reducing intra-operative contamination. The control group consisted 70 cases. Behavioural changes (correct use of plenum) were introduced to the first intervention group of 67 operations. Intense behavioural and systemic changes were introduced to second intervention group of 70 operations. The systemic changes introduced was the installation of new laminar flow with improved airflow from 2700m3/h to 8100m3/h. Two samples each were taken from used instruments, unused instruments and removed bones. Control swabs were also collected to make sure that contamination was not occurred during transport and culturing. Early and late intra-operative contamination was also checked. All patients were monitored for any wound discharge while in hospital and followed-up for 18 months to check whether intra-operative contamination affects post-operative infection.

Among the control group contamination was found 32.9% while in intervention group 1 it was 34.3% and in intervention group 2 it was 8.6%. Except in Group 1 (p=0.022) late phase contamination was not significantly higher than early phase contamination. During the control period wound discharge was found in 22.9% patients and 11.4% of them had wound infection later. Deep periprosthetic infection had been found in 7.1% of them in the follow-up period. Deep periprosthetic infection was found in 4.5% cases of first intervention group and in 1.4% of cases in second intervention group in the follow-up period. But none of these decreases were found statistically significant. Contamination, prolonged wound discharge and superficial surgical site infection were found decreased after both first and second intervention. But a statistically significant reduction was found only in second intervention (contamination p=0.001, wound discharge p=0.002 and superficial SSI p=0.004). This study concluded that behaviour modifications together with improved air flow system can reduce intra-operative contamination substantially.

Purpose of the study was clearly defined and a good review of the current literature has given. Gap in current research was clearly presented and justification for the study had given. Sample size seems sufficient. It is reported that “….bacterial cultures were taken during 207 random operations…” (p. 176), but no details of the sampling method used were provided. Details of interventions were given elaborately and results were discussed in detail. But only one table and two charts used to present it. The readers would have been more benefited if more tables were used to present the results. Discussions of the results were concise and findings were specific and satisfying the objective. No information on whether they received informed consent from the patients and approval form the ethical committee of the institution was missing. This arise a serious question about the ethics of this study.

It is found that laminar airflow is more effective when use in conjunction with occlusive clothing (Charnley, 1969 cited in Sandiford and Skinner 2009). While in their recent study Miner et.al (2007) compared the effectiveness of laminar airflow system and body exhaust suits found that body exhaust suits are more effective than laminar flow system in reducing infection.

For their study Miner et.al (2007) selected 411 hospitals which have submitted the claim for total knee surgery (TKR) for the year 2000 from four US States were surveyed to collect the details of use of laminar air flow system and body exhaust suits. Those hospitals which were fulfilled three criteria were included in this study. The inclusion criteria were 1) returned the survey instrument, 2) using laminar air flow system or body exhaust suits for infection control and 3) was evidence of at least one Medicare claim for TKR for the study period. Total 8288 TKRs performed in 256 hospitals between 1st January and 30th August 2000 were selected. Data on patient outcomes after total knee replacement (TKR) were collected from Medicare claims. The patients who underwent bilateral TKR were not included in this study and for those who underwent a second TKR during a separate hospitalisation during the study period, only the first procedure was included. International Classification of Diseases, Ninth Revision (ICDS-9) codes was used to identify post-operative deep infection that needed additional operation. Hospitals were grouped as users or non-users for both laminar airflow and body exhaust suits. “Users” were defined as those who use any of these methods in more than 75% procedures and “non-users” were those use any methods less than 75%. The over-all 90-day incidence of deep infection, subsequent operation was found required only in 28 cases (that is 0.34%). Analysis found that the risk ratio for laminar airflow system was higher (1.57, 95% confidence interval 0.75-3.31) than body exhaust suits (0.75, 95% confidence interval 0.34-1.62). Study found that there were no significant differences in infection between hospitals that use specific either protective measure.

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Other than mentioning few studies researchers failed to provide any background of the research problem. Methods used for this study were explained concisely. Even though the sample size was large, limited number of events (28) were there to be observed. Analysis was based on this small number of events; this may have affected the result. Not many variables were included in this study, and researchers didn’t mention how they controlled some possible confounders. Researchers were successful in identifying the advantages and limitations of the study. Results were properly presented in tables.

Instead of expensive laminar air-flow system, installation of well-designed ventilation system is found beneficial. Scaltriti et.al (2007) conducted a study in Italy to examine effectiveness of well-designed ventilation system on air quality in operation theatre. They selected operation theatres of a newly built 300 beds community hospital which have ventilation system designed to achieve 15 complete outdoor air changes per hour and are equipped with 0.3 µm, 99.97% HEPA filters. All these satisfy the condition for a clean room as per ISO 7 standard. Passive samples of microbiological air counts were collected using Tripticase Soy Agar 90 mm plates left open thorough out the duration of the procedure. Active samples were also collected using a single state slit-type impactor. Total 82 microbiological samples were collected of which 69 were passive plates and 13 were active. Air dust was counted with a light-scattering particle analyser. Details of the surgery, number of people in the room, door opening rate and estimated total use of the electrocautery unit were also collected.

It was found that there were positive correlations between particle contamination, surgical technique (higher risk from general conventional surgery), electrocauterization and operation length. Door opening rate was found negatively associated. Researchers suggest that this may because when theatre door open a turbulent air flow blows out of the operating room which may result decrease in the dust particles. No association was found between particle contamination and number of people present at the time of incision. Researchers suggest that human movement rather than human presence is the factor that determines airborne microbial contamination. It was found that average particle concentration in the theatres did not exceed the European ISO 14 644 standard limits for ISO 7 clean room, and so concluded that well-designed ventilation system is effective in limiting particulate contamination.

Uncultivable or unidentifiable organisms can also be a reason for surgical site infections. It may be difficult to identify such organisms through standard culture techniques (Tunney 1998). Clarke et.al (2004) conducted a quantitative study to examine the effectiveness of ultra-clean (vertical laminar flow) theatres in preventing infections by unidentifiable organisms. They used the molecular technique, Polymerase Chain Reaction (PCR), to detect bacteria presence. Their study compared the wound contamination during primary total hip replacement (THR) performed in standard and ultra clean operation theatres. 20 patients underwent primary THR from 1999 to 2001 were recruited for this study. Patients with previous incidents of joint surgery or infection were excluded. The standard operation theatres had 20 air changes per hour and CFU count was 50 CFU/m3, while ultra-modern theatres had 530 air changes per hour and CFU count was 3 CFU/m3.

For all surgeries same infection control precautions were used. Two specimens each of pericapsular tissues were collected from posterior joint capsule both at the beginning and at the end of the surgery (total 80 samples). Patients were given antibiotic prophylaxis after taking the first specimen. All these samples were underwent Gram stain and culture to detect bacterial colonies and Polymerase Chain Reaction (PCR) to detect bacterial DNA.

Among the 20 specimens taken form the standard operation theatres at the beginning of the surgery only 3 were found positive with PCR, while from the ultra-clean theatres only 2 were found positive. None from both theatres found positive with culture. Samples from the standard theatres taken at the end of the surgery, 2 found positive by culture and 9 found positive by PCR. The contamination rate in the standard theatre at the end of the surgery found significantly greater than the beginning (p=0.04). Samples taken from the ultra-clean theatres, none was positive by culture while only 6 were positive by PCR. Statistical analysis found that contamination rate at the end of the surgery is not statistically different than the start (p=0.1). It was found that there were no statistically significant difference in overall contamination rate (p=0.3) between standard and ultra clean theatres. (I will add critique of this study here)

NURSES’ ROLE IN INFECTION CONTROL

Understanding the source of contamination in operating theatre and knowing the relationship between bacterial virulence, patient immune status and wound environment will help in improving the infection rates (Byrne et al 2007).

Nurses are responsible to take a proactive role in ensuring safety of their patients. To improve patient outcome, it is necessary for the nurses to take lead role in environmental control and identifying hazards through environmental surveillance (Neil 2005). Non-adherence to the principle of asepsis by surgical team is identified as a significant risk factor of infections. Hectic movement of surgical team members in the operating room and presence of one or more visitors were also found as major causes of SSI (Beldi G 2009). Nurses and managers should emphasise on controlling factors like the traffic in theatre, limiting the number of staff and reinforcement of strict aseptic technique (Allen 2010). Creedon (2005) argues that infections can reduce up to one third if staffs follow best practice principles. For better outcome staffs needs additional education and positive reinforcement.

Nurses have a vital role in the development, reviewing and approving of patient care policies regarding infection control. Nurses are not only responsible for practicing the aseptic techniques but also responsible for monitoring other staff for their adherence to policies. They are responsible for developing training programmes for members of staff. Educating the environmental services personnel like technicians, cleaners will not only improve their knowledge in patient care but also provide a sense of commitment in patient outcomes (Neil 2005).

Perioperative nurses can contribute in research regarding theatre ventilation system through organised data collection and documenting evidences. Nurses can contribute in giving optimum and safe delivery of care in areas where environmental issues can put the patient at risk. Knowledge is changing fast, so it is important that staff must keep themselves up to date. Continues quality improvement is needed and it should be based on evidence based research and on-going assessment of information (Hughes 2009).

CONCLUSION

Reviews of current research shows that still there is a lack consensus on the effectiveness of laminar airflow in infection control. Studies include in this review has used either clinical outcomes (infection or reoperation rate) or intermediate outcomes (particle count or bacterial count) to evaluate the effectiveness of laminar flow. Kakwani et.al (2007) found that re-operation rate was lower in laminar airflow theatres but Brandt et.al (2008) found SSI rate was high in hospitals with laminar flow. Clarke et.al (2004) found that contamination was not significantly different in ultra clean theatres compared to standard theatres equipped enhanced ventilation system. Supporting this finding Scaltriti et.al (2007) found well designed ventilation system is effective in reducing contamination.

Study by Knobben et.al (2006) found that combination of systemic and behavioural changes are required to prevent intra-operative contamination. Miner et.al (2007) found that there were no significant differences in infection between hospitals that use laminar airflow and body exhaust suits.

From these studies it can be concluded that use of laminar airflow alone can guarantee infection prevention. Behavioural and other systemic changes are necessary to enhance the benefits of laminar airflow. Evidence shows that conventional theatres equipped with enhanced ventilation system can prevent infection effectively, this can be consider as an alternative for expensive as laminar flow system.