Biological monitoring during exposure to the anesthetics isoflurane and sevoflurane

Exposure to traces of inhaled anaesthetic agents may impair the health of the operating theatre personnel. Although no cause-effect relationship has been found, most public health authorities recommend various occupational exposure standards to minimize possible health risks. If metabolites of the substances are known, biological monitoring is an alternative to the monitoring of the operating theatre's air. The new anaesthetic agent Sevoflurane is considerably more transformed to fluoride than Isoflurane. Concerning fluoride there exist Biological Tolerance Values of 4.0-7.0 mg fluoride (F-) per gram creatinine (Crea). The aim of our study was to compare the fluoride excretion under the occupational exposure to sevoflurane and isoflurane. By the means of a direct-reading instrument trace concentrations of sevoflurane, isoflurane, and nitrous oxide were measured during 40 anaesthetic procedures. Urine samples were collected before (Z1) and after the workshift (Z2), and in the morning of the next day (Z3). The analysis was done by the means of an ionselective electrode. The personnel-related concentrations (median, range) were 0.50 (0.16-7.04) ppm isoflurance and 27.36 (5.87-467.10) ppm nitrous oxide, and 0.79 (0.15-1.95) ppm sevoflurane and 17.74 (2.45-84.20) ppm nitrous oxide. The resulting fluoride values presented at Z1, Z2, and Z3 as median (range) during exposure to isoflurane were 0.15 (0.11-0.53), 0.19 (0.11-0.53), 0.20 (0.11-0.31) mg F-/g Crea, and 0.15 (0.10-0.46), 0.22 (0.13-0.44), 0.23 (0.15-0.69) mg F-/g Crea during exposure to sevoflurance, respectively. The trace concentrations were clearly under 10 ppm for the volatile substances and 100 ppm for nitrous oxide. The values are comparable to data recorded under similar working conditions. The measured fluoride values were low and remained under the legal tolerance values. Under the described conditions potential health risks were low.