The concentration of isoflurane (Forane) in the ambient atmosphere was determined in 11 operating theaters of 5 hospitals in Italy. The concentrations of isoflurane in the ambient air exceeds the recommended time-weighted average exposure levels (median value: 113 μmol/m3). Isoflurane was detected in the urine of 45 exposed subjects (anesthetists, surgeons, and nurses). A significant correlation was found between the isoflurane concentration in urine produced during the shift (Cu, nmol/l) and isoflurane environmental concentration (C1, fimol/m3) (Cu - 0.243 x C1 + 3.712) (r -.90). The results show that the urinary isoflurane concentration can be used as an appropriate biological exposure index. The authors suggest a biological exposure index of 18 nmol/l (3.4 μg/l). This is the biological value obtained after 4 h of an average environmental exposure to 81 limol/m3 (2 ppm).
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