Background: Sevoflurane reacts with CO2 absorbents, resulting in the generation of breakdown products. The concentrations of sevoflurane breakdown products in a low-flow system within 5 h have been reported, but concentrations in low-flow anesthesia exceeding 5 h or in closed-circuit anesthesia have not. In this study, the breakdown products of sevoflurane in closed-circuit anesthesia exceeding 5 h were examined.
Methods: Closed-circuit sevoflurane anesthesia was administered to ten patients. Laboratory tests of hepatic and renal function were performed before and after anesthesia. Gas samples were obtained from the inspiratory limb of the anesthesia circuit, and breakdown products were analyzed by gas chromatography. The temperature of the soda lime was measured during anesthesia.
Results: Among the breakdown products of sevoflurane, two products, CF2 = C(CF3)-O-CH2F (compound A) and CH3OCF2CH(CF3)OCH2F (compound B), were detected. Compound A was detected in all measurements, and its concentration reached 19.5 +/- 5.4 ppm 1 h after anesthesia and decreased after 5 h. The highest concentration observed for compound A was 30.0 ppm. Compound B was detected in seven of the ten patients; its concentration was 0.17 +/- 0.37 ppm after 0.5 h of anesthesia and remained at similar concentrations thereafter. The highest mean temperature of the soda lime was 46.0 +/- 1.7 degrees C. Postanesthetic clinical laboratory tests showed no abnormalities in hepatic or renal function associated with anesthesia.
Conclusions: Two breakdown products were detected in the patients anesthetized with sevoflurane using a closed-circuit technique. No abnormalities were observed during anesthesia, and no evidence of hepatic or renal dysfunction was noted in postoperative laboratory tests.