A Cohort Study of Traffic in Theatre as a Risk for Surgical Site Infection at Three Tertiary Hospitals in the Copperbelt Province, Zambia

Operating theatre–related nosocomial infections cause an estimated 10% of surgical site infections (SSI) in postoperative wounds and result in increased hospital stays, catastrophic costs to the patient and hospital, and increased morbidity and mortality [1,2]. In 1948, it was suggested that restricting the traffic by head count and door-openings of the operating room could reduce the risk of developing SSI [3]. One of the first studies to suggest that traffic by head count in the operating theatre or the number of doors opening were a risk factor for SSI, though not reaching statistical significance, was in 1998 [4].

Operating-theatre room nosocomial infections are difficult to ascertain and have not been accurately described [5]. SSI occurring in a postoperative wound have been described as superficial SSI (occur in skin and subcutaneous tissue at a depth that is superficial to deep fascia and that occur within 30 days), deep SSI (occur in deep to the fascia and involve muscles, peritoneum, and other soft tissues), organ specific (eg appendicular abscess following appendicectomy), and implant-associated (osteomyelitis following open reduction and internal fixation) [6–8].

The rate of SSI arising from wound contamination is influenced by the quality of the operating room, and therefore by microorganisms causing operating- room SSI to originate from 2 sources [9,10]. First, is endogenous flora on patients (contaminated or dirty wound, lack of prophylactic antibiotics, comorbidities, and coinfections), operating-theatre staff, and those coming in and out of theatre room. Second is exogenous flora on equipment, instruments, and consumables brought into the operating room [11,12]. Endogenous florae are commonly in droplets and contaminated body fluids that encounter wounds, dispersed by theatre traffic as vectors of microorganisms that disrupt the laminar flow of air in theatre [13]. Exogenous florae are in dust or in aerosol-dispensed microorganisms that contaminate wounds in the operating room, equipment, and instruments used in treatment [14].

The disturbance of the laminar air flow in ventilated operating rooms, which can be caused by traffic in the theatre, compromised theatre-room structure, or unnecessary theatre-door-opening, are responsible for dispensing exogenous flora. Contaminated fabrics and wound dressings that result from poor hospital environment hygiene can cause SSI [14]. Comorbidities in the patient such as diabetes mellitus, malnutrition, immunosuppression, old age, smoking, and obesity are risks for operating room SSI [15].

Preventing SSI arising in theatre rooms requires cleaning and disinfection of the theatre, equipment, and instruments, as well as staff behavioural change [16]. This protects the patient from preventable causes of SSI [16]. Controlling traffic in theatre reduces chances of transmitting airborne infections that can cause SSI in patients [17]. The theatre rooms at the study sites are flooded with staff who train students and students from various universities (nursing, medical, and postgraduate surgical trainees) since these institutions are university teaching hospitals. While the prevalence of SSI is high at the 3 institutions, it has not been established if door-opening and the high number of people present in theatre while a procedure is undertaken, comprising students and staff, is a risk for the development of SSI.

The aim of this study was to assess whether theatre traffic arising from staff and students present in theatre rooms is a cause of SSI and to determine the rate of SSI originating from theatre traffic and door-opening at the 3 tertiary institutions in the Copperbelt Province of Zambia.

2.1 Study Design
This was a prospective observational cohort study conducted over a period of one year.

2.2 Setting
This study was conducted in the Copperbelt Province of Zambia at 3 tertiary hospitals, namely Ndola Teaching Hospital, Kitwe Teaching Hospital, and a tertiary public hospital, Arthur Davison Children’s Hospital.

2.3 Participants
Participants were recruited into the study by convenient sampling method. This involved recruiting all patients undergoing a surgical procedure and consented to participate in the study, in the one year study period. The surgical condition was either emergency or elective. Those who did not receive surgical treatment, whether they had a surgical condition or not, were excluded. A total of 1122 participants were included in the study.

2.4 Variables and Definitions
This study primarily focused on development of superficial SSI defined by WHO as postoperative infections occurring in the operative wound, 30 days post-surgical procedure. The WHO Surgical Unit-based Safety Program, advising that surveillance of SSI can be done with any number of patients, was used.

The usual population in theatre comprises the anaesthetist; a surgeon with or without an assistant, a theatre nurse, and a theatre runner; and a theatre porter. These individuals constitute the operating-theatre team, although more staff may be added to this team. Students from the 3 teaching hospitals are present in theatre for teaching purposes. The theatre team and students comprise the theatre population. Theatre runner was present during the entire theatre procedure and recorded the head count and number of door openings from beginning to end of each surgical procedure. Head count was categorised into groups of ≤5, 5–10, 11–15, >16, while door openings <6 and 6–10. For infection prevention, the local hospital theatre staff generally restricted head count of observers in theatre and door openings during all operative procedures to reduce SSI rates. Head count of trainees and observers was generally restricted to groups of 15 individuals. Head count above 15 accounted for door openings, delivery of theatre consumables and oxygen supplies, supervision or consultations or trainees joining on to observing a rare or interesting case for learning. If there were less cases to observe in theatre and more trainees, theatre head count would go above 16 individuals.

2.5 Data Collection
The participants were followed up for 30 days and monitored for development of SSI. Wound care was standardised for all participants.

The presence of SSI was based on symptoms and signs of SSI, including identification of the microorganism, its antimicrobial sensitivity, and its resistance patterns. Symptoms included pain and pus draining from wound site, while signs included redness, swelling, pus drainage, and wound dehiscence. Pus swabs collected were subjected to microscopy, culture, and sensitivity testing. Phone follow-up was also used along with patient wound-site pictures. Informed consent was obtained from patients or guardians. Information was collected using perioperative and postoperative forms and phone follow-up forms. Wound surveillance was conducted for 30 days from the time of the procedure.

Designed data collection sheets, modified from the WHO Surgical Unit-based Safety Program surveillance form, were used, and data were entered into Excel for cleaning and analysis.

Ethics approval was obtained from the Tropical Diseases Research Centre Ethics Review Committee, IRB registration number 00002911, and the National Health Research Authority.

2.6 Statistical Analysis
Using SPSS, descriptive analysis was performed using proportions and frequencies for categorical variables, means with standard deviations, and medians with interquartile ranges for skewed data. Associations of variables were analysed using the chi-square test for categorical variables.

3.1 Baseline Characteristics
A total of 1122 participants were included. Of these, 468 were females and 654 were males.

The results in Figure 2 show that the majority (25.7%) of the participants were aged between 21–30 years, followed by those between 31–40 years (24%), with the fewest 10 years and below (0.1%). However, age was not significant for the development of superficial SSI, with a p-value 0.319.

Figure 3 shows that most participants had clean wounds (40.8%) followed by those with dirty wounds (33%). This figure also shows that the combination of contaminated and dirty wounds represents those who presented with infection at the time of surgery (PATOS). Wound class and development of superficial SSI was not significant, with a p-value of 0.921.

Figure 4 shows that the majority of participants had emergency surgery; however, the difference between the groups is minimal and not significantly related to development of superficial SSI, with a p-value of 0.235.

3.2 Superficial SSI Rates
Pus swab samples were submitted for 218 participants (19.4%) as shown in figure 5, representing those that developed superficial surgical site infection for analysis; 904 participants (80.6%) had no infection after initial surgical and antimicrobial treatment, of a total of 1122 subjects.

3.3 Head Count Analysis
Table 1 shows no association between the number of people in the operating theatre and the development of superficial SSI. The highest SSI rate (27.3%) was observed when more than 16 people were present in theatre; however, this did not reach statistical significance (p=0.057). These results show that theatre traffic by head count of individuals present in the theatre operating room is not a significant cause of superficial SSI at the 3 tertiary institutions.

3.4 Door Opening Analysis
Table 2 above shows a strong association between the number of entries into the operating theatre (theatre traffic) and the development of superficial SSI. This information is based on analysis of those who developed superficial SSI (19.4%) from a population of 1122 subjects. In these 218 subjects, entry into theatre at the time they were being operated on was significant.

At the 3 referral hospitals that receive referrals from the 5 northwestern provinces of Zambia (North-Western, Luapula, Northern, Muchinga, and Copperbelt), the prevalence of superficial SSI is 19.4%, as shown in Figure 5. The operating rooms at the 3 tertiary institutions have a high number of trainees from various training institutions who participate in procedures as part of their training. It was therefore important to investigate if traffic in theatres at these 3 hospitals by head count was a risk for our patients who develop superficial SSI. This study showed that theatre traffic by head count during procedures was not significantly associated with superficial SSI, as confirmed by others [7,18–20]. In this study, head count as traffic in theatre had p-values not statistically significant for the various categories of patients (16 people), as shown in Table 1.

Participants were aged 0 to 70 years old, with the majority being those in the age range 21–30 years old, as shown in Figure 1. However, age was not a risk factor for development of superficial SSI. The majority of our participants presented with clean wounds, at 40.8% (Figure 2), and wound class was not a significant risk for development of superficial SSI, with a p-value of 0.921. Although a majority of our patients underwent emergency surgery, surgical urgency was not a risk factor for surgical site infection, with a p-value of 0.235. The rates of developing of SSI in the various wound class categories have been analaysed into separate data for publication. They have not been included in this study.

Yokoe et al [21] have argued in their study that limiting traffic into the operating room can lower the rate of developing superficial SSI. Brandit et al [22] have reported that reducing traffic in theatre by head count and restricting movement in the operating room reduces dispersal of organisms that cause superficial SSI. Knobben et al [23] have reported that wearing appropriate theatre attire and reducing unnecessary movement reduces risk for development of superficial SSI.

Therefore whether a patient undergoing an operation develops superficial SSI will depend on the behaviour of the people in the operating room (and not the number of people), the administration of prophylactic antibiotics, effective ventilation of the operating room and host factors or risks in the patient being operated on [15,24,25]. Postoperative outcomes for development of superficial SSI include host factors such as wound class, comorbidities (malnutrition, diabetes mellitus, advanced HIV/AIDS), smoking, and preoperative optimisation of the patient before a surgical procedure [26–28].

The Association of Operating Room Nurses (AORN) guidelines, which are considered the gold standard guidelines, recommend designing patterns of traffic flow for patients and staff in the operating room and creating 3 zones there [29]. These guidelines include reducing head count to the minimum required for the procedure, reducing door-opening and unnecessary movements in and out of theatre to maintain laminar flow of air, and wearing appropriate attire in theatre. The AORN guidelines also zone the operating theatre into 3 zones: restricted (operating room where surgical attire should be worn and adherence to aseptic techniques of infection prevention), semi-restricted (operating theatre corridors, scrub-up areas, and storage rooms in theatre), and unrestricted zones (hospital environment out of operating theatre and hospital corridors). The AORN zoning guidelines aim to reduce traffic flow and not head count and to establish the cleanliness level appropriate to the zone. The AORN guidelines are used at the study sites to prevent infection and reduce the risk of SSI.

This study showed that the number of entries into the operating room was significantly associated with development of superficial SSI. Several studies have supported such findings [29–32]. However, disturbance of the laminar flow, as a risk for SSI, determined by the number of microorganisms present in the air of the operating room per unit volume, (at which it may be determined that such a concentration of airborne microorganisms compromise the quality of air and become a risk factor for superficial SSI) is yet to be established [18,19,29]. Therefore entries into theatre room in this study, have been observed to be associated with the risk for developing superficial SSI.

Ascribing traffic into and out of the operating room as being a mechanism by which there is change in the number of microorganisms per unit volume of air that can cause superficial SSI has not also been established as a risk factor for superficial SSI [33]. Therefore, determining how many times an operating room door is opened whether these can be deemed as a risk for superficial SSI is also not established [33]. Even though longer operating procedures increase the likelihood of door-opening, the actual number of door-openings that creates a risk for SSI has not been established, and therefore redosing of antibiotic prophylaxis is practiced [20,34,35]. The findings of this study need to be validated by a larger randomised control trial.

Therefore, control of the operating room environment and equipment sterility reduces sources of microorganisms that can cause superficial SSI [20,34].

Study Limitations

1. Multivariable analysis was not performed; therefore, results are not presented with adjusted effect estimates such as odds ratios and confidence intervals.
2. The observed association between door openings and SSI may be confounded by factors such as procedure duration and case complexity, which were not adjusted for in this analysis.

This cohort study has found that traffic in theatre by head count was not associated with the risk, however, the number of door-openings was significantly associated with superficial SSI. Several studies have concluded that door-openings and not traffic by head count may disturb laminar airflow and increase airborne contamination, which has been proposed as a mechanism for SSI, although this was not directly assessed in this study. However, this is not established in our study.