2168 Occupational exposure to inhalation anesthetics

Pregnant women employed in operating rooms (ORs) may be chronically exposed to physical work load as well as to low doses of waste anesthetic gases. Volatile and gaseous inhalation anesthetics arc administered as mixtures in different combinations, and can be delivered to the patient through an endotracheal tube or via a face-mask. Until several years ago, ventilation systems were apparently not efficient enough in preventing exposure to relatively high levels of anesthetics. Modern ORs are usually equipped with scavenging systems which significantly rcduce the exposure of the OR staff to the gases. Nevertheless, measurements indicate that the staff may still be exposed to significant levels of waste anesthetic gases, since there is no hermetic way to avoid leakage of these gases into the workspace. The effectiveness of the preventive measures varies from one place to another, and proper maintenance is critical. Workers in dentistry often use nitrous oxide that is not administered via endotracheal tubes. The fact that common anesthetic gases easily cross the placenta means that they may pose a higher risk for the fetus and the mother (Herman 2000, Cordier 1992).

From the occupational safety perspective, different countries have set limits on the operating room air concentrations of anesthetic agents. For example, a maximum concentration of 25 ppm of nitrous oxide in the operating room is recommended in the USA. In Germany, a maximum workplace concentration of 100 ppm is considered harmless. However, it is often difficult to impose these rules, and therefore routine monitoring is advisable.

Over the past three decades, research exploring the effects of inhalation anesthetics on pregnancy has focused on fertility problems and the rate of congenital anomalies. Research findings regarding the effects of anesthetics on the developing fetus have been inconclusive (Tannenbaum 1985, Pharoah 1977). An increased rate of spontaneous abortion has been reported among OR personnel exposed in the course of their work, which has been attributed to chronic exposure to inhalation anesthetics, particularly nitrous oxide (Hemminki 1985, Vessey 1980). in a retrospective study by Rowland (1995), female dental assistants who worked more than 3 hours a week with nitrous oxide, and not using scavenging equipment, had a higher rate of spontaneous abortion. It is, however, difficult to eliminate the possibility that these effects may be a result of confounding factors such as stress, coffee consumption, smoking, and body position, as well as a tendency to miscarriage (Rowland 1995, 1992). Moreover, similar findings have not been confirmed in other epidemiologic studies.

Only a few studies have looked into the effects of maternal occupational exposure to ancsthctics on the newborn. Several studies have identified outcomes of low birth weight and shortened gestational age at delivery (Ericson 1979, Rosenberg 1978, Pharoah 1977, Cohen 1971) in occupationally exposed groups. There are very few studies on the long-term development of children born to women occupationally exposed to anesthetic agents. One such study was performed recently (Ratzon 2004). The study population included 40 children (aged 5-13 years) born to female anesthesiologists and nurses working in ORs, who were thus exposed to waste anesthetic gases, and 40 children born to female nurses and physicians who worked in hospitals during their pregnancy but did not work in ORs. No differences were noted, regarding developmental milestones, in the exposed group as newborns or at the ages of 5-13 years. However, the mean score of gross motor ability was significantly lower in the exposed versus the unexposed group, and their scores on the DSM-lll R Parent-Teacher Questionnaire (PTQ), which measures inattentlon/hypcractivity, was higher in the exposed group, implying a higher rate of inattention. The level of exposure was significantly and negatively correlated with fine motor ability and the IQ score. However, these groups of children are too small to be conclusive.

Occupational exposure to injectable anesthetics does not impose any specific problem in pregnancy.

Recommendation. It is safe to work in modern operating rooms with most volatile anesthetics because of the state-of-the-art scavenging systems in place, but it is Important to monitor the concentrations in the air. Levels of anesthetics should not exceed the maximal allowable concentrations (Threshold Limit Value, TLV) for each agent. The data on congenital anomalies are reassuring, while the data on spontaneous abortions and developmental delay need further corroboration, Work with nitrous oxide In rooms without scavenging systems should be reduced In pregnancy, whenever possible.

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