You can't see them, but they're there: microscopic blood and tissue particles, waste anesthetic vapors, latex residue and, yes, even cyanide. At any given time during a surgical procedure, one or more of these airborne contaminants could be swirling around in your ORs. Here are 8 measures you can take to protect both patients and staff from the potentially harmful aerosols that are, in some cases, inevitably generated during surgery.

1. Perform an air quality check-up. We begin with a job for your biomedical services folks: Measure your air quality. Use the following metrics to determine the current indoor air quality of your ORs, says Andrew Streifel, hospital environmental specialist at the University of Minnesota. This information will help you set realistic expectations for what the existing conditions are and plan for improvement, if needed.

• Particle counts. Should show a 90% to 95% reduction in microns in the OR compared to outside its doors. This evaluation is a rate reduction, not a specific number. Particle counts are an easy check to know if your ventilation and filtration systems are working.
• Positive pressure. With the doors closed, the air pressure in your ORs should be a >0.01-inch water column (2.5 Pascals) pressure differential from the hallway's air pressure, so that air flows from clean (the surgical site, scrub area) to dirty (the hallway, air capture system).
• Air exchange rate. ASHRAE Standard 170: Ventilation for Healthcare Facilities recommends a minimum total of 20 air changes per hour and a minimum of 4 air changes of outdoor air per hour to properly ventilate the surgical suite.
• Temperature. It's best to try to keep the temperature in the OR between 68 ?F and 75 ?F; keeping it below 72 ?F helps to keep the surgeon cool and comfortable. The most important thing with ventilation and air velocity over the surgical site is to overcome the thermal plume that's generated over the patient. The surgeons, the lights and the patient's body all generate a certain amount of heat. This heat causes the air to rise over the surgical site and the "make-up" air for that air movement comes from below — a dynamic that may allow shed microbes to be deposited in the surgical site. If the airflow over the surgical site is maintained around 35 linear feet per minute downward, that is sufficient to overcome most air movement (thermal plume). The laminar-like regime of this airflow, while turbulent, keeps the air above the surgery cleaner than that below the table.

2. Perform regular maintenance on your ventilation system. Signs that something's not right with your ventilation system include strange smells in the OR, "unexplained" surgical site infections or staff complaining of feeling hot, fatigued or irritable. Understanding how your ventilation system was designed and how it is functioning will help prevent problems before they start, as well as arm you with the basic knowledge you'll need to troubleshoot glitches when they arise, says Mr. Streifel.

"Maybe once a year, have an air balance engineer come in and do measurements," says Russ Olmsted, MPH, CIC, president-elect of APIC and an epidemiologist in infection prevention and control services at St. Joseph Mercy Health System in Ann Arbor, Mich. He notes that you should already have a waste anesthesia gas analysis conducted periodically throughout the year (OSHA recommends you do this quarterly). The professional who comes in to do those checks is also going to measure whether the OR has positive pressure (see "Tissue Test Helps You Maintain OR Positive Pressure"), how many air changes are being made per hour and the temperature and humidity levels in the room — all important parameters to let you know whether your HVAC system and filters are working.

3. Check and change your filters. Your filter installation should be checked after new filters are installed and yearly thereafter, says Mr. Streifel. "Gaskets, clips and spacers need close scrutiny to ensure the integrity of the ventilation filtration system." He says most filter systems last about 18 months, depending on conditions. "The rule of thumb for changing filters is to change them when you're at about 80% of the manufacturer's recommended pressure drop."

4. Run the HVAC system 24/7. Mr. Olmsted recalls the story of a surgical facility that turned off the ventilation system over the weekend in an attempt to conserve energy, only to end up with a cluster of surgical site infections linked to an unusual fungal organism. It turns out the organism had been allowed to grow in the ventilation system while it was turned off over the weekend, and then the organism was blown into the OR when the system was turned back on Monday morning. "When you have air stagnation you can get potential contamination in the system," warns Mr. Olmsted. If you're energy conscious, he suggests you dial the system down to about 15 air changes per hour over the weekend, but don't switch the HVAC off completely.

5. Clear the path of airflow. Your staff should be mindful of how the air flows in and out of your ORs. Make sure they aren't placing supplies or equipment in front of exhaust grills, which, Mr. Olmsted says, could interfere with air exchanges in the room.

6. Evacuate surgical smoke. The plume generated by laser or electrosurgery devices contains a number of toxic, mutagenic and carcinogenic contaminants, including carbonized tissue, blood, intact viruses, bacteria and harmful chemicals like cyanide and formaldehyde. Within 5 minutes of activating the electrosurgical unit, these contaminants travel at a rate of about 40 mph in a concentration ranging from 60,000 to more than 1 million particles per cubic foot, explains Kay Ball, PhD, RN, CNOR, FAAN, who has done extensive research on the dangers of surgical smoke. It takes another 20 minutes after the unit is shut off for the air quality to return to normal. In her research, Dr. Ball has found that perioperative nurses exposed to surgical plumes report a number of respiratory problems and ailments, including eye, nose and throat irritation, allergies, headaches, dizziness and nausea, at a rate higher than that of the general population.

The general ventilation system in the OR isn't enough to protect your staff from these hazards. The Occupational Safety and Health Administra-tion recommends that you have a smoke evacuator available for every room where surgical smoke is generated, that you evacuate all smoke generated during a case and that the device be held within 2 inches of the surgical site. The most effective way to remove contamination from laser or electrosurgery plume is to use "local exhaust, a suction tip either close by or incorporated right into the device," says Mr. Olmsted. "By removing it almost as soon as it's generated, you contain it very well." Evacuators built directly into the electrosurgical pencil produce a vortex motion to remove the plume, which Dr. Ball says is more effective than using a separate system of tubing hooked up to an evacuator, which uses a unilateral motion to remove the smoke. Your smoke evacuators should have an ultra-low penetration air filter with 0.1 micron filtration to ensure nearly 100% capture of particulate matter.

Purchasing the equipment is a step in the right direction, but your biggest challenge may be getting your surgeons and staff to remain diligent in evacuating smoke plumes. To help raise awareness of the hazards of surgical smoke and the necessity of removing it before the air becomes contaminated, AORN has a Surgical Smoke Evaluation Tool Kit (free for members) available at www.aorn.org/practiceresources/toolkits.

7. Scavenge waste anesthetic gases. Your surgical team is at risk of exposure to waste anesthetic gases (such as nitrous oxide and halogenated agents like desflurane and sevoflurane) that can leak from the anesthesia machine, connectors and accessories. Although research is limited, studies have shown that waste gases could have negative side effects for healthcare workers, such as neurological damage or reproductive problems. OSHA advises facilities to keep "any exposure to waste and trace gases to the lowest practical level" to ensure the safety of the surgical team.

While your HVAC system plays a role in diluting and removing trace gases from the air, you should employ additional engineering controls to address leaks at their source. OSHA?recommends an anesthetic gas scavenging system that "traps waste gases at the site of overflow from the breathing circuit and disposes of these gases to the outside atmosphere." The scavenging system should collect waste vapors at their source and carry them out of the OR, while limiting positive and negative pressure variations in the breathing circuit. Good practices on the part of your anesthesia and nursing personnel are also key to keeping the air clear of waste gases, says Mr. Streifel. According to "Anesthetic Gases: Guidelines for Workplace Exposures" (www.osha.gov/dts/osta/anestheticgases), your staff should:

• inspect anesthesia equipment daily for any potential malfunctions or leaks;
• have face masks available in a variety of sizes and create an effective seal when applying them;
• inflate cuffs and position airway devices, such as laryngeal masks, appropriately;
• take care when filling vaporizers to minimize spillage, and clean any spills immediately;
• flush the breathing system with non-anesthetic gases before removing any airway management devices from a patient; and
• turn off vaporizers when not in use.

8. Keep doors closed and foot traffic to a minimum. Although maintaining positive pressure in the operating room helps keep dirty air flowing away from the surgical site and out into the hallway or exhaust vents, it's still important to keep the door closed as much as possible during a case. "There's good evidence that opening the door, even once, does alter the air flow, requiring the system to respond to that change in pressure," says Mr. Olmsted. "The ideal is a well-sealed operating room, and you want to minimize in and out traffic." AORN also suggests that you keep the number of people in the OR, as well as conversation and movement among those people, to a minimum. "An increase in airborne microorganisms can occur with an increased number of people present," according to AORN's Recommended Practice for Traffic Patterns in the Perioperative Practice Setting. "Movement, talking, and uncovered skin areas can contribute to airborne contamination."

Even at a teaching hospital, where residents and medical and nursing students can increase the number of people present during a case, there are steps you can take to minimize traffic in the OR. As part of a larger infection prevention initiative in recent years, West Virginia University Hospitals began limiting the number of people who can be present in the OR suite during a case (12 maximum), encouraging personnel to enter the OR from the restricted corridor where sterile supplies are kept, and equipping anesthesia providers and residents with wireless phones for use in communicating with people in the OR rather than having to come in and ask questions in person, says Dawn Yost, RDH, RN, BSN, CNOR, manager of nursing operations and the sterile processing department. Mr. Olmsted has even seen facilities tape the OR doors shut during a case. He notes that limiting traffic has the added benefit of reducing distractions for the surgeon and the support staff, letting them focus solely on the procedure.

Trust, but verify
"Never assume that just because you've got a ventilation and filtration system in place, it must be working," says Mr. Streifel, who's seen filters that haven't been changed in OR ventilation systems for years because the pressure gauges did not move. "Was the air so clean that it never loaded the filters, or was there bypass around the filters? Unfortunately, these situations often aren't discovered until surgical wound infections become apparent."

Understanding how your air quality control system works, performing regular maintenance on it and training staff to do their part by managing surgical smoke and waste anesthetic gases can help shield patients and staff from the health hazards of airborne contaminants.