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Harlan C. Amstutz, MD

AAOS Now

Published 10/1/2007
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Amy Kile

Clean air in the OR

How OREF-funded research fits in the fight against intraoperative infection

Preventing surgical infection is fundamental to total joint replacement (TJR) procedures, so it’s no wonder the topic has been the subject of numerous research studies. With the support of a grant from the Orthopaedic Research and Education Foundation (OREF), Harlan C. Amstutz, MD, was among those who first sought to establish a correlation between operating room (OR) ventilation systems and the reduction of intraoperative infections—more than three decades ago.

“Intraoperative infections were the plague of the very earliest joint replacements done in this country,” says Dr. Amstutz, professor emeritus and former chief of orthopaedic surgery at the University of California at Los Angeles (UCLA), who is best known for his work on total hip replacements and for founding the Joint Replacement Institute. “Unfortunately, the operative and immediate postoperative wound provides an excellent environment for the development of infection.”

An ounce of prevention
Because of the danger of wound sepsis, it’s important for physicians to control the sources of possible contamination. Airborne contamination had been a topic of concern for nearly a century by the time TJR emerged in the late 1960s.

Although infections can develop at the site of TJR prostheses months or even years after the operation—a complication that may lead to costly and traumatic revision surgeries—some surgeons thought that reducing contamination during surgery should reduce the risks of both immediate, intraoperative infections and periprosthetic infection. Orthopaedic surgeons, therefore, began practicing several precautionary measures, including administering prophylactic antibiotics; requiring surgical teams to wear whole-body, exhaust-ventilated suits to control the amount of contamination transferred to the patient during surgery; reducing traffic in the OR; carefully preparing and cleaning the OR and the wound site; covering exposed hair and skin; and using double gloves.

Advent of laminar air flow
In the 1960s, Sir John Charnley, MD, a Lancashire, U.K.-based orthopaedic surgeon renowned for inventing the first truly successful total hip replacement procedure, introduced a clean air enclosure. This laminar airflow system filtered out small bacteria-laden particles from air coming into the OR. According to Dr. Amstutz, Dr. Charnley believed that preventing contamination in the OR atmosphere could reduce the potential for intraoperative infection among TJR patients, perhaps negating the need for prophylactic antibiotics.

Dr. Charnley’s clean air enclosure recirculated a continuous flow of highly filtered, bacteria-free air under positive pressure in the operating field and removed air contaminates generated during surgery.

By the 1970s, orthopaedic surgeons were debating whether such an airflow system truly reduced the risk of infection. As Dr. Amstutz began his career at UCLA, he found that university ORs lacked laminar airflow systems and decided it was an excellent opportunity to research the value of the technology.

Putting it to the test
“Our plan was to equip the rooms with laminar airflow and measure how effective it was over the old, standard operating room,” Dr. Amstutz explains. “The idea was that perhaps antibiotics would not be necessary following surgery if the OR was quite sterile.”

Enlisting the expertise of Harry Buchberg, MS, an engineer in the UCLA School of Engineering, Dr. Amstutz set out to control the operating environment and compare the air quality in the old and new ORs. Together, Mr. Buchberg and Dr. Amstutz designed a study using the Reyniers slit sampler to test the air in the UCLA operating rooms.

“The Reyniers slit sampler samples the air and counts the number of particles, which are then plated on blood agar,” Dr. Amstutz explains. “The bacterial colonies are counted and the types of organisms are identified to determine the level of circulating contamination that could potentially cause an infection.”

Dr. Amstutz collected data from the existing ORs before and after the laminar airflow systems were installed and noted a precipitous drop in organisms.

“We were able to reduce the infection rate to less than 1 percent, but we decided to continue with prophylactic antibiotics,” Dr. Amstutz says of the results. “The reduced infection rate correlated with the reduction of particles. Additionally, the organisms identified were less virulent than in the old rooms. This led to further studies comparing the effectiveness of horizontal laminar flow vs. vertically oriented flow—which Charnley favored—in preventing infections.”

Harlan C. Amstutz, MD
Laminar flow system similar to those Dr. Amstutz used for his studies on operating room ventilation systems and the reduction of intraoperative infections.

For more information on laminar airflow in the OR, see the AAOS Bulletin, June 2006, at www.aaos.org

Research draws interest by NASA
The research grant that Dr. Amstutz received from OREF aided this study, which also gained the attention of the National Aeronautics and Space Administration (NASA).

“Harry Buchberg was a consultant for NASA,” Dr. Amstutz explains. “They became involved because they needed the cleanest possible rooms to perform the studies that would dictate the protocol for their space programs…. So NASA was extensively involved in this clean room technology.”

In addition to interest from NASA and discussion of the results at several symposia, the findings of the OREF-funded study were published in the September 1975 issue of Clinical Orthopaedics and Related Research.

Two-pronged approach
The initial hypothesis of the laminar flow research was that the use of antibiotics would be unnecessary in a sufficiently clean operating environment. Today most surgeons take advantage of both measures to prevent infection.

“It turns out that there’s not really a good enough reason to stop using antibiotics—although there is always a concern that continued use will lead to the development of resistant organisms,” Dr. Amstutz says. “But to really prevent infection, most surgeons want both a modern environment—with a high rate of air exchange to purge the operating room of contaminants—and continued use of antibiotics.”

OREF grant a “catalyst”
Dr. Amstutz says he quickly understood the importance of his initial research in building the case for further investigation. His initial OREF grant was just as important in attracting additional funding.

“When I came to UCLA, I was still quite young,” he says. “When you arrive at the university—even as chairman—they give you a title, authority, and some salary lines for faculty, but they do not provide money for research. So you have to seek grant support.”

The OREF grant was one of the first that Dr. Amstutz and his colleagues received at UCLA. “That grant was definitely the catalyst that allowed us to activate our study to assess the laminar flow system’s effectiveness in reducing intraoperative infections.”

Stimulated by his research grant, Dr. Amstutz went on to study other causes of infections and ways to prevent them. He developed a research program that involved orthopaedic residents and fellows, as well as representatives from internal medicine, infectious diseases, and engineering. This multidisciplinary group received several National Institutes of Health grants in the bioengineering field.

The goal: Getting to zero
The most important aspect of any research, Dr. Amstutz says, is how it ultimately affects patients. His original OREF-funded laminar flow research is no exception.

“Although infections can still occur years after surgery, we were trying to prevent intraoperative infections of any joint replacement,” Dr. Amstutz says. “For TJR procedures done today, the risk of infection is considerably less than 1 percent for most OR environments in large centers. Ideally, of course, we would like it to be zero. The work continues.”

Amy Kile is a public relations specialist with OREF. She can be reached at kile@oref.org