Capture efficiency of CONTRAfluran™ absorbers for sevoflurane in routine anaesthesia practice: a prospective observational single-center study

Abstract Background Volatile anaesthetics are potent greenhouse gases. Recapturing volatile anaesthetics using active charcoal absorbers on the exhaust port of anaesthesia machines might reduce their negative climate impact. Previous studies investigating the capture efficiency of absorbers have been performed mostly under circumstances that differ from everyday clinical routine. We here investigated the capture efficiency of the CONTRAfluran™ absorbers for sevoflurane in routine anaesthesia practice. Methods In this prospective single-centre study, we collected 20 consecutive CONTRAfluran™ absorbers from two different operating rooms (ORs) after they were maximally saturated. After storage and transport, the sevoflurane was recaptured from the absorbers by the absorber manufacturer. To calculate the capture efficiency, we divided the amount of recaptured sevoflurane by the total sevoflurane consumption during the use of the absorbers, which was obtained by comparing the weight of the sevoflurane bottles before and after refilling the vaporizers. Results We monitored 738 balanced anaesthesia cases. A total of 14.2 kg sevoflurane was used and 4.9 kg could be recovered, yielding a capture efficiency of 34%. The capture efficiencies differed significantly between the ORs, with 47.8% in the OR with shorter anaesthesia durations and frequently inhaled inductions versus 21.4% in the OR with longer anaesthesia durations. We saw a 3% weight loss over time during storage. Conclusions If CONTRAfluran™ absorbers are used until they are fully saturated, almost one-third of the sevoflurane can be recaptured. The capture efficiency may be affected by various patient- and procedure-related factors, including the fresh gas flow used and the duration of anaesthesia.