Dissociative Anaesthesia During Field and Hospital Conditions for Castration of Colts

Marntell S, Nyman G, Funkquist P: Dissociative anaesthesia during field and hos­pital conditions for castration of colts. Acta vet. scand. 2006, 47, 1-11. - The princi­pal aim of this study was to evaluate dissociative anaesthesia for castration of colts dur­ing field conditions. Three dissociative anaesthetic protocols were evaluated during castration of colts in an animal hospital. The protocol considered to be the most suitable was thereafter evaluated during castration of colts under field conditions. Respiratory and haemodynamic parameters and the response to surgery were determined during anaesthesia. All horses breathed air spontaneously during anaesthesia. Under hospital conditions 26 colts were randomised to receive one of three anaesthetic protocols: Romifidine and tiletaminc-zolazepam (RZ); acepromazine, romifidine and tiletamine­zolazepam (ARZ); or acepromazine, romifidine, hutorphanol and tiletamine-zolazepam (ARBZ). The surgeon was blinded to the anaesthetic protocol used and decided whether supplemental anaesthesia was needed to complete surgery. Under field conditions 31 colts were castrated during anaesthesia with the ARBZ protocol. All inductions, anaes­thesia and recoveries were calm and without excitation under both hospital and field conditions. Surgery was performed within 5-20 minutes after the horses had assumed lateral recumbency during both hospital and field castrations. Under hospital conditions some horses needed supplemental anaesthesia with all three anaesthetic protocols to complete surgery. Interestingly, none of the horses castrated with protocol ARBZ under field conditions needed additional anaesthesia. Cardiorespiratory changes were within acceptable limits in these clinically healthy colts.