1. Department of Veterinary Anaesthesia and Analgesia, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh EH25 9RG, UK
2. Department of Small Animal Surgery, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh EH25 9RG, UK
3. Bristol Vet Specialists, Unit 10, More Plus Central Park, Madison Way, Severn Beach, Bristol BS35 4ER, UK
4. Equine Clinical Studies, Diagnostic Imaging and Anaesthesia, UCD School of Veterinary Medicine, University College Dublin, D04 W6F6 Dublin, Ireland