Capture of isoflurane from anaesthetised dogs and cats following methadone, medetomidine and ketamine

Background Volatile anaesthetic agents contribute to climate change and reducing this impact is a commendable ambition. We evaluated the efficiency of a veterinary capture device for isoflurane (VET-can/VET-dock, SageTech Veterinary) in anaesthetised cats and dogs. Methods Purposeful sampling was used to recruit enough animals undergoing isoflurane general anaesthesia to fill one VET-can to at least 95% capacity. The vaporiser and VET-can were weighed pre-and post-anaesthesia to determine in vivo mass transfer (MT) of isoflurane and water. Primary outcomes were capture efficiency (isoflurane delivered: desorbed, %) and in vivo mass transfer (MT). Secondary outcomes were associations between MT and patient characteristics and anaesthesia variables. Results Thirty anaesthetics (21 cats; 9 dogs) were required to fill the VET-can to capacity. There was an overall capture efficiency of 81% isoflurane and 4% water. In vivo MT was 86% (57-100). There was no correlation between patient characteristics or anaesthesia parameters and in vivo MT. Limitations Interchangeable use of sidestream and mainstream capnography resulted in a difference in times to end-tidal isoflurane 0%. Conclusions Capture efficiency was 81%. The device prevented a mean release of 3.2 kgCO2e for each 20-minute anaesthetic period, approximately the equivalent of 13 miles driven in an average UK car.