Health and Safety

Often animal research endeavors involve surgeries. Surgical anesthesia is carried out in everything from bench top “knockout boxes” to fully equipped operating rooms depending on the species. In research, we encounter animals of all sizes, from mice to horses and everything in between. If animal surgeries are performed, anesthetic agents pose a potential exposure concern. In this article, we discuss who is at risk, the most commonly used agents and their health effects, signs and symptoms of exposure, how to determine if your anesthesia operations present exposure concerns, and, finally, what to do to minimize or eliminate exposures.

Who should be concerned?
This might seem apparent to most of us, but just so no one feels slighted or left out we will state the obvious anyway. There are two areas where exposures are most likely to occur: operating rooms and recovery rooms. The employees most at risk include surgeons, anesthesiologists, operating room nurses, technicians and attendants, and recovery room nurses and attendants. Even with the best automatic ventilation and scavenging systems, anesthetic gases can pose an exposure risk when the gases escape into the room from anesthetic delivery equipment. Leaks can occur at tank valves, breathing circuit connectors, tubing and hose defects, during hookup and disconnection of the equipment, and during induction and from poorly fitting masks and nose cups. In recovery rooms exposures can occur from the anesthetic agent being exhaled by the patient.¹

What agents are we concerned about and why?
The compounds known as halogenated anesthetic agents are the main anesthetics in use currently. These are isoflurane, enflurane, desflurane, sevoflurane, and halothane. Studies have shown that acute (high concentration-short term) exposures to these agents may produce headaches, irritability, fatigue, nausea, drowsiness, problems with coordination and judgment, and liver and kidney disease. In addition, acute exposures to very high concentrations can produce depression of the central nervous system (CNS) functions, respiratory and cardiovascular systems, and seizures. Chronic (low concentration-long term) exposures have been linked to miscarriages, genetic damage, and cancer.²

Even so, OSHA has not established permissible exposure limits (PEL) for these halogenated anesthetic gases. Other agencies and organizations have set recommended exposure limits. The American Conference of Governmental Industrial Hygienists (ACGIH) set Threshold Limit Values (TLV) of 75 parts per million (ppm) for enflurane and 50 ppm for halothane as 8-hour time-weighted averages (TWA).³ The National Institute of Occupational Safety and Health (NIOSH) has recommended an exposure limit (REL) of 2 ppm as an upper limit or “ceiling” value for a maximum one hour exposure period due to concern over worker exposure and the serious potential health effects.²