Sevoflurane degradation to compound A in anaesthesia breathing systems.

Determination of an effective rate constant and activation energy allowed the application of steady-state theory to predict concentrations of compound A from sevoflurane concentrations, fresh gas flow rate, absorbent temperature and amount of absorbent. Studies by eight research groups were compared. Lower concentrations of compound A than predicted were observed at low flow rates, suggesting that its degradation by the absorbent is important in limiting the maximum observed concentrations in closed and low-flow breathing systems. Trial-to-trial and batch-to-batch variations in compound A concentrations were observed in model system tests of commercial and pilot-plant absorbents. Chemical modification of the absorbent with glycerol lowered concentrations of compound A, possibly by formation of a nucleophilic addition product. An ideal chemical scavenger would remain stable and non-volatile in the absorbent before irreversibly reacting with compound A to form a stable non-volatile product.