Plasma Inorganic Fluoride and Intracircuit Degradation Product Concentrations in Long-Duration, Low-Flow Sevoflurane Anesthesia

Plasma inorganic fluoride (F-) concentrations in long-duration, low-flow sevoflurane anesthesia were studied to assess effects on renal and hepatic function. The intracircuit concentration of degradation product generated by reaction between sevoflurane and CO2 absorbant was also determined. Ten patients undergoing prolonged surgery of 10 h or longer received sevoflurane anesthesia at 1 L/min. Plasma F- concentration was measured and clinical laboratory tests were performed. Intracircuit gas was analyzed to measure the concentration of degradation products. Plasma F- concentration increased during anesthesia, and decreased 3 h after termination. Individual maximum plasma F- concentrations were 38.8-88.6 mumol/L (56.6 +/- 4.7 mumol/L, mean +/- SE). Minimum alveolar anesthetic concentration (MAC) hours (1 MAC = 2.05%) exposure correlated with individual maximum plasma F- concentration (r2 = 0.68, P < 0.01). CF2 = C(CF3)-O-CH2F (compound A) was the only degradation product detected in the circuit. Its individual maximum concentrations were 13.6-35.1 ppm (24.3 +/- 2.4 ppm). Postanesthesia clinical laboratory tests showed no renal impairment and only mild hepatic dysfunction that was not associated with anesthesia. Hyperfluorinemia and minute quantities of compound A were detected following long-duration, low-flow sevoflurane anesthesia.