Compound A concentration and the temperature of CO2 absorbents during low-flow sevoflurane anesthesia in surgical patients.

Sevoflurane, a new inhalational anesthetic, is metabolically broken down into several decomposition products in the presence of CO2 absorbents. One of the products, CF2=C (CF3) OCH2F (compound A), which appears to be the most toxic, was quantitated in 20 surgical patients subjected to more than 3 h of anesthesia using a low-flow anesthesia circuit. To minimize the variables in the reaction velocity between sevoflurane and the CO2 absorbents, we maintained the sevoflurane concentration at 2%. Wakolime-A, one type of soda lime, resulted in the highest increase in compound A concentration. The peak concentration was 27.1±3.1 ppm, less than one-tenth of the LC50 (50% lethal concentration) of compound A, which was previously reported as 420 or 400 ppm in rats. We also measured the temperature in CO2 absorbents, which had been reported to influence compound A production. The elevation in the temperature was 27.9±1.3°C in Wakolime-A, 29.4±8.4°C in Baralyme, and 31.0±5.0°C in Sodasorb II. Further studies are needed to assess the safety and efficacy of sevoflurane.