OR Air Contamination Standards Needed to Control SSI Risk

Author: Tom Rosenthal

Anesthesiology News

Air contamination standards for microbial aerosol particulates in the OR are needed to reduce the risk for SSIs, said Charles E. Edmiston Jr., PhD, at the Association for Professionals in Infection Control and Epidemiology 2018 annual conference.

The technology now exists that can accurately measure viable aerosol microbes in the OR, as well as to clean the air to substantially reduce the risk for contamination and infection of surgical wounds. So now is the time to adopt these standards, said Dr. Edmiston, who is an emeritus professor of surgery at the Medical College of Wisconsin, in Milwaukee.

The surgical team itself and viable aerosol contaminants— either already present or brought into the OR when the doors are opened—provide the primary sources of airborne microbes that cause ssIs, according to Dr. Edmiston, who conducted an innovative 18-month in situ air sampling analysis of 70 separate vascular surgical procedures.

On a hunch, Candace M. Krepel, MS, then supervisor of the laboratory, decided to culture the sink and recovered a strain of S. maltophilia; she discovered that whenever the faucet was turned on and water hit the sink, it created an aerosol, she said. Anyone walking through the anteroom when the aerosol was present could carry the bacteria into the OR, which could then contaminate a surgical wound.

“We were able to make a direct molecular connection with what was in the sink and what was in the infection by comparing DNA patterns,” she said.

Door openings during surgery are linked to elevated airborne bacteria, agreed Annette Erichsen Andersson, RN, CNOR, PhD, a senior lecturer in the Department of Anesthesiology/Surgery at Sahlgrenska Academy at the University of Gothenburg, in Sweden, who has researched OR air contamination.

In 120 air samples taken in three ORs during 30 orthopedic trauma surgeries, air quality exceeded less than 10 colony forming units (CFU)/m³ in 52 of 91 samples, Dr. Andersson wrote (Am J Infect Control 2012;40[8]:750-755). “One of the most important findings of the present study is the highly negative impact of traffic flow in the OR on bacterial contamination of the air close to the wound; that is, a high rate of door openings was associated with high rates of CFU/m³values.”

Dr. Andersson said the study found that only 7% of the door openings during surgery were for expert consultation, whereas the leading reason doors were opened—26%—were for supplies, followed by 20% for staff breaks; 14% of the door openings occurred while the wound was open. “Door openings for logistic reasons could all be avoided by telephone communication.

“Door openings related to social visits and for no detectable reasons together accounted for 27% of the traffic flow, possibly reflecting an OR culture that accepts door openings for no special reason,” she wrote.

In an interview, Dr. Andersson said, “It is of great importance that managers and staff acquire knowledge and are motivated to adhere to behavior guidelines in the OR to secure air cleanliness.”

Dr. Edmiston added: “Every surgical practitioner is inserting a biomedical device, and these devices are absolute magnets for bacteria.” The implant or the device—even sterilized under the most rigorous procedures—are at risk for contamination because of OR aerosols or staff shedding, he noted.

As a result, Dr. Edmiston said, “every surgical wound is contaminated at closure, and whether or not that rises to the level of infection is dependent on factors of the virulence of the organism and comorbidity risk of the patient, which makes the patient vulnerable to infection.”

Javad Parvizi, MS, MD, FRC, an orthopedic surgeon at the Rothman Institute in Bensalem, Pa., wrote in a paper with Dr. Edmiston that the cost of periprosthetic joint infections (PJIs) in the United States is projected to reach nearly $1.6 billion by 2020 (Am J Infect Control2017;45[11]:1267-1272).

The number of arthroplasties in the United States is expected to exceed 3.8 million annually by 2030, with the incidence of PJIs to be less than 2.5%, and the PJI rate is associated with a 2% to 7% mortality rate, according to the researchers.

“Although the pharmaceutical and computer industries enforce stringent air quality standards on their manufacturing processes, there is currently no U.S. standard for acceptable air quality within the OR environment,” they wrote.

Existing engineering standards measure particle size to gauge the effectiveness of a hospital’s air circulation system, Dr. Edmiston noted. “The problem with that kind of standard, which has been around for many, many years, is that it doesn’t get down to whether these particles are viable. They are not evidence-based standards to document patient risk,” he said.

“We need to move away from this strategy of measuring total particulates, most of which are nonviable,” Dr. Edmiston said. “Viable particulates give us a much better measure of risk. We are trying to make this direct correlation between microbial populations that occur in the OR and causal epidemiology that results in ssIs in our patient population.” Dr. Andersson agreed that measuring viable particulates is more relevant.

World Standards

Dr. Edmiston said the United States should adopt proposed European Union/World Health Organization standards that set less than 50 CFU/m³ as the permissible level of aerosol microbial contamination in general ORs (class II), whereas permissible limits for orthopedic, cardiac and transplant ORs would be less than 10 CFU/m³ (class I). He said he was optimistic the EU would adopt the standards next year.

Although the proposed EU standards are sufficient as a general recommendation, the patient’s individual susceptibility to infection should be considered, according to Dr. Andersson.

“It might very well be that it is necessary to adjust the levels below 10 CFU during surgery if the patient is suffering from conditions or has risk factors that have negative effects on the immune system,” said Dr. Andersson, who is also a nurse consultant at Sahlgrenska University Hospital.

Dr. Edmiston said these proposed standards are reachable. Existing technology can reduce viable particulates by 56% to 88% in the OR, he said. “I have no doubt entering the market will be a whole variety of innovative technologies whose focus is to reduce microbial burden within the OR environment.”

David Weber, MD, MPH, a professor of medicine, pediatrics and epidemiology at the University of North Carolina at Chapel Hill School of Medicine, said he fully supports Dr. Edmiston’s call for research to validate OR air contamination standards that are feasible to achieve and have been demonstrated in rigorous scientific studies to reduce ssIs.

“He is right; we need more research to develop a standard testing strategy to determine the level of risk, and we need research to validate that it is feasible and possible to achieve those levels to control those risks,” said Dr. Weber, who is on the board of the Society for Healthcare Epidemiology of America.

Because there is no standardized method of testing, Dr. Weber questions whether the capability exists to meet the standards proposed for the EU. “It is a valid area of study,” he said. “I support evidence-based standards. We have to have standardized test strategies and the ability to meet those standards.”

Standards should be feasible and modifiable as technology improves. “It does not make sense to adopt a standard we do not know how to meet,” Dr. Weber said.

“It is truly confounding that rigorous air quality standards are applied to the drug and computer chip manufacturing industries, whereas the same rigor has not been embraced to provide a safe and effective OR environment for surgical patients,” Dr. Edmiston said.

“To lower the risk to patients, we need to do studies to standardize testing strategies, and we need to do research to assess how best to change the OR to meet those standards,” Dr. Weber said. “What is not clear is who will finance that research.”

Although the CDC is financing some of this research, the level of funding for research is small. “We need larger amounts of funding to answer the questions Dr. Edmiston is asking.”

Historically, there has not been a great deal of interest in the issue of microbial aerosols in the OR, according to Dr. Edmiston. “Contamination from microbial aerosol was always a kind of back-burner issue.”