Chapter 101

### INTRODUCTION

Anesthesiologists and other operating room (OR) personnel are chronically exposed to trace amounts of waste anesthetics gases, including nitrous oxide (N2O) and halogenated agents (halothane, isoflurane, desflurane, sevoflurane, etc) throughout their careers. Since the 1960s, various studies have implicated this chronic exposure as causing numerous adverse health effects, though no definitive link has been established. Though it has not been definitively proved that trace amounts of waste anesthetic gases are detrimental, it is nevertheless reasonable to be aware of possible effects and to take appropriate precautions to limit exposure. By remaining diligent of contamination sources and taking appropriate measures to minimize the concentrations of waste anesthetic gases, anesthesiologists can protect themselves and other OR personnel from potential harm.

### EPIDEMIOLOGICAL STUDIES AND EXPOSURE LIMIT RECOMMENDATIONS

In 1967, A. Vaisman published the results of a survey of 15% of the anesthesiologists in the Soviet Union. The survey suggested that anesthesiologists more frequently experienced fatigue, exhaustion, and headache and that female anesthesiologists had higher rates of spontaneous abortion than other physicians. Several papers followed, with some reporting increased rates of spontaneous abortion, congenital abnormalities, and cancers among health-care personnel exposed to waste anesthetic gases, while other studies found no such increased risk.

Due to rising concerns over the possible deleterious effects of chronic waste anesthetic gas exposure, in 1972, the American Society of Anesthesiologists (ASA) Ad Hoc Committee on Adverse Reactions to Anesthetic Agents met with the National Institute of Occupational Safety and Health (NIOSH) to review the literature and retrospectively survey OR personnel. The survey, published in 1974, demonstrated increased risk of spontaneous abortion, congenital abnormalities, cancer, and hepatic and renal disease among female OR personnel. This data resulted in an NIOSH recommendation to scavenge all waste anesthetic gases, a practice which had not previously been a standard. NIOSH also issued the following recommended exposure limits for waste anesthetic gases, given in parts per million (ppm) and measured as a time–weight average during the period of anesthetic administration:

• N2O: 25 ppm

• Any halogenated agent used alone: 2 ppm

• Any halogenated agent used in combination with N2O: 0.5 ppm

These recommendations, which remain in effect today, were somewhat arbitrarily derived from a 1974 study conducted by D.L. Bruce. The study looked at the effect of exposure to anesthetic gases on the cognitive and motor skills of 40 male volunteers. Their performance was significantly reduced after exposure to 500 ppm N2O with or without 15 ppm halothane. However, no effect was seen with exposure to 25 ppm nitrous oxide with 0.5 ppm halothane.

Throughout the 1980s, the ASA continued to work toward uncovering possible effects of waste anesthetic gases. In 1985, an ASA-commissioned study analyzed the data from six prior investigations and was unable to establish an increase in relative risk for any evaluated outcome. An independent review conducted in the same year found that the studies ...

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