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Section I: Symposium: The Papers Presented at the Hip Society Meeting 1999: II. Infection

Operating Room Environment

Ritter, Merrill A. MD

Editor(s): Barrack, Robert L. MD

Author Information
Clinical Orthopaedics and Related Research: December 1999 - Volume 369 - Issue - p 103-109
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Lidwell et al10 showed a direct correlation between sepsis rates in total joint replacement and environmental operating room contamination. Also, most bacterial contamination gets transferred to the wound secondarily after first landing on other supposedly "sterile surfaces".22 Therefore, to reduce sepsis it must be understood where the bacteria are coming from and how effective are present day control measures.

The source of the environmental bacteria in the operating room has been shown to be the operating room personnel,14 and the quantity of environmental bacteria is related directly to the amount of bacteria the personnel shed and the number of people present.4

Various means to control such environmental bacteria such as scrub clothes, sterile gowns, head covers, masks, hooded exhaust equipment, laminar flow, and ultraviolet light all have been speculated as to their efficiency. It is the author's aim to evaluate the effectiveness of these means of environmental controls in containing the environmental contamination.



An operating room suite consisting of eight similar rooms located around a sealed hallway was the source for the data presented. Twenty 150-mm air settle plates were placed peripherally about the hallway and six were placed in each operating room, 4 feet from the floor. In four operating rooms all the doors remained shut, in two operating rooms, the door connecting to the corridor was left open, and in two operating rooms the door was swung open and closed 50 times per hour. All air settle plates were opened and closed by an investigator who had to enter the closed operating rooms, which produced some contamination. Ten people dressed in scrub pants, shirts, shoe covers, and hoods paced evenly throughout the hallways, not in the operating rooms, for 1 hour.12 There were four runs during which all the personnel wore fiberglass face masks and four runs in which they did not wear fiberglass face masks.12

In another experiment using one operating room, five subjects dressed in scrub suits, shoe covers, and hoods walked uniformly around the operating room for 30 minutes. Twenty sessions were studied, 10 in which the subjects wore surgical face masks and 10 in which the subjects did not wear surgical face masks. Six air settle plates were placed throughout the room at the level of 4 feet.12

During actual orthopaedic and total joint surgery, five separate operating room conditions were sampled (a conventional operating room with 15 to 25 air changes per hour and no laminar airflow, horizontal laminar airflow without walls, horizontal laminar airflow with walls that were either extended or not extended, and vertical laminar airflow without walls). All samples were obtained with air settle plates, positioned one at the wound, one on the back table, and four about the periphery of the operating room table behind the surgical team.15

Stacks of 13 sterile hemostats were placed on the back sterile instrument table for operations involving open heart surgery and bilateral total hip replacements, both of which would last more than 3 hours. The hemostats were not used during the procedure and remained in racks where they were removed and placed into a jar of thioglycolate broth either with the gloved hand of the scrub nurse (10 procedures) or sterile pickups (10 procedures) without being touched by the gloved hand. The open heart surgeries were done in a conventional operating room without laminar airflow and the bilateral total hip replacements were performed in a room with horizontal laminar airflow.13


To determine the effect of nonsterile scrub clothes, such as dresses, pants and shirts, and shirts tucked into pants with the feet enclosed in fabric, the environment was sampled at 4 feet by air settle plates. Four runs were done for each condition.6

There were three types of sterile gowns sampled for surface contamination: cloth, paper, and plastic. Gown surface contamination was evaluated by compression rodak plates, sampling five different sites on the surface of the gown, one at each shoulder, one on either side of the waist, and one at the zyphoid process. This was done directly after applying the sterile gowns and 30 minutes after use within an operating room. There were three runs for each gown, and four gowns per run.1

Next, in a mock setting, the environmental effect of various gown protections were evaluated for 60 minutes with air settle plates placed around the periphery of an operating room. The gown preparations were a plastic wrap around gown with a cloth hood, face mask, and gloves versus a hooded exhaust gown, and finally, scrub clothes. There were three runs for each gown, scrubs, or both.14

Head Cover

In a mock situation the environmental effect of the use of a surgical cap, a surgical hood, or no surgical hood was evaluated. This also was done by air settle plates placed about the room during a 30-minute period. This was done three times for each condition with four people present for each run.14

Body Exhaust

To determine the effect of the body exhaust on the laminar airflow conditions, the wound site was sampled during actual total hip surgery when all operating room personnel wore body exhaust equipment and a hooded gown versus sterile gowns, paper hoods, and masks.14



The average colony forming units per square foot per hour in an operating room with closed doors was 13.3, with open doors was 24.8, and with swinging doors was 19.4. The only statistical difference was between the opened and closed doors (p < 0.05). Wearing a face mask in the hallway did not statistically influence any of the counts obtained in the hallway or in the operating room (Table 1).

Environmental Contamination* in the Operating Rooms and Sterile Corridor

In Table 2 it can be seen that either by volumetric or air settle plate sampling there was greater than a 92% reduction in the bacteria at the wound and back table and greater than a 60% reduction in the bacteria around the periphery of the room behind the surgical team when laminar airflow was used.

Comparison of Contamination Found in Conventional Versus Laminar Airflow Operating Rooms

When looking at the various types of operating room laminar airflow conditions, there was a statistical reduction in the amount of bacteria at the wound site when laminar airflow was used for only total hip procedures (Table 3). This reduction was not as great with the use of vertical laminar airflow, which also required the operating room personnel to use a hooded exhaust gown.

The Colony Forming Units per Square Foot per Hour for Three Different Laminar Airflow Conditions During Total Hip Replacement Surgery Only

As seen in Tables 4 and 5, 1/2 of the instruments were contaminated in a conventional operating room when the scrub nurse took the instruments and put them into the jar, 30% were contaminated in the conventional operating room without being touched, and less than 1% were contaminated in a laminar airflow operating room. These results also are seen in the average number of contaminated hemostats per case: more than 1/2 of the hemostats were contaminated when the scrub nurse picked up the instrument, 1/3 were contaminated when the sterile pickups were used, and less than 1% were contaminated in a laminar airflow room.

Average Number of Contaminated Hemostats per Case (12 Cases Sampled)
Average Number of Contaminated Instruments per 15 Minutes for 10 Patients


There was no statistical difference in the environmental contamination despite the type of nonsterile scrub clothes that were worn by the various personnel.

There was a 33% reduction in the surface bacteria on the paper gowns (1.66 colony forming units per rodac plate) compared with the cloth gowns (2.51 colony forming units per rodac plate), a 71% reduction using plastic gowns (0.708 colony forming units per rodac plate), and a 57% reduction in contamination on the plastic gowns versus paper gowns. If the head was enclosed completely, such as it was with the plastic gown, there was a statistical reduction in the amount of surface contamination on the shoulders versus the waist, although this was not evident in the cloth or paper gowns.

There was a 51% reduction in environmental bacteria using the plastic gown versus the scrub clothes, a 69% reduction using body exhaust hooded gown versus scrub clothes, and a 38% reduction when comparing the hooded exhaust gowns with plastic wraparound gowns (Table 6).

Comparisons of Different Types of Surgical Garments on Environmental Contamination

Head Cover

The length of the hair of the operating room personnel and the means of enclosing the hair with various head covers showed no statistical difference in the amount of bacteria contamination of the environment (p > 0.1) when the operating room personnel did not wear a head cover, 336 colony forming units per square foot per hour were found, when the operating room personnel wore caps, 462 colony forming units per square foot per hour were found, and when the operating room personnel wore hoods, 214 colony forming units per square foot per hour were found.


The wearing of a surgical face mask in the hallway or the operating room had no effect on the bacterial counts in either the hallway or the operating room. In a previous study9 done in an operating room, there was 447.3 colony forming units per foot per hour when the individual wore the face mask and 449.7 colony forming units per foot per hour when he or she did not wear a face mask. As noted previously, with people walking about the hallway, the face mask had no effect on the environmental bacterial counts in the hallway or the operating room (Table 1).

Body Exhaust

Looking at the data from air settle plates obtained during actual total joint replacement surgery with horizontal laminar airflow, there was no difference in the amount of colony forming units per square foot per hour at the wound site with the use of body exhaust or face masks, paper hoods, and no exhaust (Table 7).

Wound Air Settle Plate Counts*


Sepsis after total joint replacement is a devastating sequelae that surgeons must avoid and because the environmental contamination is related directly to sepsis, all measures of data driven protection should be evaluated as to how each one might help. The environment of an operating room when left overnight or without people in it is basically bacteria free. It is not the filtering potential of the air coming into the room that is important. The personnel who enter the operating room carry the bacteria.4,14 Therefore, it is the control of the human transmission of bacteria that will control the bacterial contamination within the operating room.

Approximately 30% of all operating room personnel carry Staphylococcus aureus; however, 13% of men shed greater than 10,000 bacteria per minute as compared with 5% of postmenopausal and 1% of premenopausal women.4 The first control of shedding is, therefore, the use of an inclusive sterile gown.5,14,18,19,23 The use of a sterile body exhaust is even more effective.8,14,19 However, this means that in an operating room everyone must wear an inclusive sterile gown and exhaust hood and this may not be acceptable to the anesthesiologist, unscrubbed nurses, and visitors. The use of head covers and masks did not significantly lower the contamination.14,15 Laminar airflow or some type of environmental control is the best means by which environmental bacterial contamination is reduced.2,3,7,11-13,15,16,17,21 However, laminar airflow must be used properly because as reported by Salvati et al16 any impedance of the course of the air only increases the amount of bacterial contamination downwind about the wound. Other environmental controls such as ultraviolet light work by not reducing the bacteria, but by killing the bacteria present. The use of ultraviolet light is just as effective, if not more effective and less expensive, but requires that all operating room personnel be covered completely to avoid ultraviolet burns.2,3,20

The data presented indicate that the colony forming unit per square foot per hour in the environment of a conventional operating room is between 300 and 400 units. The wound is contaminated first by direct fallout and second by contact with gloves, instruments, and other items that are contaminated by the environment and then introduced into the wound. This is even a larger source of contamination than the environment itself.

The amount of bacteria in an operating room should be reduced by reducing the number of personnel,4 using inclusive gowning, using some type of environment control system, and by keeping the operating time to a minimum. This, hopefully, will reduce the amount of bacteria within the air and on the sterile field, and reduce the incidence of sepsis.


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© 1999 Lippincott Williams & Wilkins, Inc.