[The compound A concentration in a low-flow anesthesia circuit using the new CO2 absorbent SPHERASORB]

CO2 absorbents convert sevoflurane to fluoromethyl-2,2-difluoro-1-(trifluoromethyl) vinyl ether (compound A), whose toxicity in rats raises concern regarding the safety of sevoflurane in a low-flow system. SPHERASORB is a new CO2 absorbent which does not contain KOH. However, the reaction between SPHERASORB and sevoflurane has not been examined. We compared compound A concentration in a model circuit using SPHERASORB and the commonly used Sodasorb II. The anesthesia circuit was circulated with fresh gas flow at a rate of 1 l.min-1 containing 2% sevoflurane. Compound A concentration was measured hourly and the temperature of CO2 absorbent was monitored. The maximum concentration of compound A in the circuit was 12.2 +/- 1.4 ppm for SPHERASORB and 18.6 +/- 0.4 ppm for Sodasorb II (P < 0.05). The maximum temperature of SPHERASORB was lower than that of Sodasorb II (P < 0.05). SPHERASORB can reduce compound A formation, compared to Sodasorb II.