Occupational Exposure of Operating-Theater Personnel to lsoflurane and Nitrous Oxide

Liver-function abnormalities have been observed in humans exposed to inhalation anesthetics and experimental studies have revealed changes in microsomal enzyme-system activity caused by inhalation of a variety of anesthetics. This study assessed liver function by means of a simple noninvasive test: Measuring urinary D-glucaric acid (UDGA) excretion in 24 subjects [selected from an anesthesia staff and exposed to a mixture of anesthetics of about 1 ppm (40 mmol/m₃) of isoflurane (Forane®) and below 100 ppm (4090 mmol/m₃) of nitrous oxide] matched with 24 controls. In the exposed group the postoperative UDGA mean level (3.68 mmol/mol creatinine) was significantly (p < 0.05) increased compared to the preoperative mean level (2.92 mmol/mol creatinine), which did not differ from the controls' mean level (2.83 mmol/mol creatinine). Concerning the difference between UDGA concentration in urine collected before and after exposure (ΔUDGA), the majority of the subjects (8 out of 9) included in the lowest exposure class (urinary isoflurane levels lower than 5.3 nmol/L) had lower ΔUDGA levels (≤1.4 mmol/mol creatinine), whereas the majority of the subjects (5 of the 6) in higher exposure classes (urinary isoflurane levels higher than 10.6 nmol/L) presented higher ΔUDGA levels (> 1.4 mmol/mol creatinine) (p < 0.02). This observation supports the hypothesis of a relationship between the exposure level and the biological response evaluated by determining UDGA excretion. Although it is not possible to clarify the mechanism responsible for the increase in UDGA excretion in anesthesia staff, this result can be regarded as a response of liver metabolism to environmental and working conditions.