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May 1997
Volume 61 |
Number 5
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| Trace Anesthetic
Gases in the Operating Room |
Diana G. McGregor, M.B., Chair
Task Force on Trace Anesthetic Gases
Committee on Occupational Health of Operating Room Personnel
Since 1967, when Vaisman in the Soviet Union made his observations
on the health of anesthesiologists in the operating room,1
there has been speculation that trace anesthetic gases may have
a harmful effect on operating room personnel. Vaisman surveyed
15 percent of anesthesiologists in the Soviet Union and found
that they were affected by a number of potentially unfavorable
factors, including inhalation of anesthetic vapors, emotional
stress, sustained attention to details of work and excessive work,
which may have led to a deterioration in their health, including
a deleterious effect on pregnancy and the nervous system.
Many papers followed on this subject. In 1971, Cohen et al. surveyed
operating room nurses and found an increased incidence of miscarriage.2
In 1972, Knill-Jones et al. recorded an increased frequency of
spontaneous abortion and congenital abnormalities in the offspring
of female anesthesiologists.3
In 1973, Corbett et al. reported an increased incidence of cancers
in nurse anesthetists in Michigan4
and the following year also reported an increase of birth defects
in that group.5
On the other hand, in 1979, Ericson found no difference in the
incidence of threatened abortions, birth weight, perinatal death
rate or congenital malformations in female operating room workers,6
and Hemminki et al., in 1985, reported no significant increase
in risk of spontaneous abortion or malformation in pregnant operating
room workers after exposure to waste anesthetic gases.7
In the mid-1970s, the ASA Ad Hoc Committee on Effects of Trace
Anesthetic Agents on Health of Operating Room Personnel8
met with members of the National Academy of Sciences, the National
Research Council and the National Institute for Occupational Safety
and Health (NIOSH) to review the literature. They commenced the
ASA National Health Survey of Operating Room Personnel. It was
planned that if the study demonstrated adverse effects of trace
anesthetic gases, scavenging practices would be recommended and
a follow-up survey would be carried out at a later date.
However, in 1977, before the ASA study was completed, NIOSH felt
it had sufficient information and published its recommendations
concerning standards, data on exposure, information about scavenging
and work practices, and methods for monitoring trace anesthetic
gases.9 The recommended standard
for halogenated agents when used alone is 2 parts per million
(ppm) in the ambient air measured on a time-weighted average.
If nitrous oxide was used as well, the standard was 0.5 ppm. The
recommended exposure level for nitrous oxide was 25 ppm. They
were all arbitrary levels and were not based on any toxic effects.
The Occupational Safety and Health
Administration (OSHA) developed technical instructions to
deal with waste anesthetic gases. Scavenging of waste gases was
recommended with regular testing of the system to ensure that
there were no leaks. It was the responsibility of the anesthesiologist
to ensure compliance with these standards. Other aspects of the
recommendations included education of employees on this subject
and medical surveillance of exposed personnel. All of these requirements
were to be monitored by OSHA.
The matter was by no means closed. Because of disagreement among
experts on the validity and interpretation of the literature,
ASA commissioned a study to evaluate previous epidemiological
investigations.8 Thus, in 1985,
Buring et al. reported the outcome of previous published reports
by combining data from six studies and calculating the relative
risk for each outcome under investigation.10
The most consistent evidence they found suggested there may be
an increase in spontaneous abortion in pregnant women who worked
in the operating room. However, these results could be explained
by accuracy of data collected from retrospective studies using
self-reported outcomes and by response/recall bias. Buring suggested
that prospective cohort studies were needed to determine if there
is an association between occupational exposure to trace anesthetics
and adverse health outcomes.
In the same year, Tannenbaum et al. also independently reviewed
the epidemiological literature.11
They determined that, due to significant flaws in the design and
conduct of the observational studies, there was inadequate evidence
to conclude that occupational exposure to anesthetic agents caused
increased rates of spontaneous abortion or congenital anomalies.
Their criticisms were based on inconsistent methodology, retrospective
collection of data, different populations studied, methods of
data collection, reliability of outcome data and low response
rates. They also concluded that further prospective studies were
necessary to state that trace anesthetics were harmful in the
workplace.
More recently, Spence and colleagues conducted a survey from
1977 to 1984 of all United Kingdom female medical school graduates
aged 40 years or less working in hospitals.12,13
They collected data on details of occupation, work practice, lifestyle,
medical and obstetric history as well as some personal details.
Of the 11,500 women surveyed, there was an 85-percent to 92-percent
response rate. They found that female anesthesiologists did not
have an increased risk of infertility and that there was no correlation
between spontaneous abortion or development of congenital abnormalities
in live-born children and the occupation of the mother, hours
exposed to the operating room environment or the use of scavenging
equipment. There was also no increase in the incidence of cancer
or neuropathy in relation to occupation.
Based on the more recent studies and the evaluations of older
epidemiological surveys, it does not appear that there are proven
hazards to personnel working in the operating room from trace
anesthetic gases. Nevertheless, scavenging is in routine use today
and is mandated by OSHA, although it has not been shown to have
had a definitive role in protecting operating room workers from
adverse health outcomes. Recently, there has been some concern
that the postanesthesia care unit (PACU) nurses may be exposed
to trace anesthetic gases because there is no scavenging in the
PACU. Levels of trace anesthetic gases in the PACU are lower than
in the operating rooms; therefore, there is no logical basis to
consider them harmful in this environment.
Since the first report by Vaisman, ASA has always maintained
an active interest in this subject, and the Committee on Occupational
Health of Operating Room Personnel has established a task force
to keep abreast of any developments in this field. The Task Force
on Trace Anesthetic Gases is currently writing a booklet to provide
information for ASA members on all the relevant facts on this
subject.
References:
- Vaisman AI. Work in surgical theatres
and its influence on the health of anaesthesiologists. Eksp
Khir. 1967; 3:44-49.
- Cohen EN, Bellville JW, Brown BW Jr. Anesthesia,
pregnancy, and miscarriage: A study of operating room nurses
and anesthetists. Anesthesiology. 1971; 34:343-347.
- Knill-Jones RP, Moir DD, Rodrigues LV,
Spence AA. Anaesthetic practice and pregnancy. Controlled survey
of women anaesthetists in the United Kingdom. Lancet.
1972; 1:1326-1328.
- Corbett TH, Cornell RG, Lieding K, Endres
JL. Incidence of cancer among Michigan nurse anesthetists. Anesthesiology.
1973; 38:260-263.
- Corbett TH, Cornell RG, Endres JL, Lieding
K. Birth defects among children of nurse-anesthetists. Anesthesiology.
1974; 41:341-344.
- Ericson A, Kallen B. Survey of infants
born in 1973 or 1975 to Swedish women working in operating rooms
during their pregnancies. Anesth Analg. 1979; 58:302-305.
- Hemminki K, Kyyronen P, Lindbohn ML. Spontaneous
abortions and malformations in the offspring of nurses exposed
to anaesthetic gases, cytostatic drugs, and other potential
hazards in hospitals, based on registered information of outcome.
J Epidemiol Commun Health. 1985: 39:141-147.
- Occupational disease among operating room
personnel: A national study. Report of an Ad Hoc Committee on
Effects of Trace Anesthetic Agents on Health of Operating Room
Personnel, American Society of Anesthesiologists. 1974; 41:321-340.
- Criteria for a recommended standard: Occupational
exposure to waste anesthetic gases and vapors. Cincinnati, OH:
US Department of Health, Education and Welfare, Public Health
Service, Centers for Disease Control, National Institute for
Occupational Safety and Health. DHEW (NIOSH) Publication No.
77. 1977:140.
- Buring JE, Hennekens CH, Mayrent SL, et
al. Health experiences of operating room personnel. Anesthesiology.
1985; 62:325-330.
- Tannenbaum TN, Goldberg RJ. Exposure to
anesthetic gases and reproductive outcome. A review of the epidemiologic
literature. J Occup Med. 1985; 27:659-668.
- Spence A. Occupational risks of the operating
room? Data from the UK ten year prospective study. Bull NY
St Postgrad. December 1985:140.
- Maran NJ, Knill-Jones RP, Spence AA. Infertility among female
hospital doctors in the UK. Br J Anaesth. 1996; 76:581P.
Diana G. McGregor, M.B., is a consultant
for the Department of Anesthesiology, Mayo Clinic, and Assistant
Professor of Anesthesiology, Mayo Medical School, Rochester, Minnesota.
She is also coordinator of Mayo's Intraoperative Anesthetic Waste
Gas Management program in the Department of Anesthesiology.
E-mail the author.
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