Standing behavior in horses after inhalation anesthesia with isoflurane (Isoflo) and postanesthetic sedation with romifidine (Sedivet) or xylazine (Rompun)

Isofluorane is a modern, only slightly depressive inhalation anaesthetic with excellent pharmacologic characteristics in use in equine medicine. In contrast to halothane, isofluorane is hardly broken down in the liver, but is eliminated by the lung. It low solubility in blood permits excellent control of anaesthesia. However, due to its swift elimination from the organism there is heightened risk of premature recovery from isofluorane anaesthesia. In this study the recovery phases of 96 horses were monitored for its duration and the animals' physical coordination. The horses were divided into four groups. Two groups were sedated with xylazine, one of which received postanaesthetic sedation with xylazine, the other saline solution only. The other two groups were sedated with romifidine, either with or without postanaesthetic sedation after general anaesthesia. In this study the horses of Group 4, sedated with 0.02 mg/kg BW romifidine at the moment of extubation, showed the best recovery phase. The number of attempts to arise was reduced and coordination was better. Similar results were obtained by postanaesthetic sedation with 0.2 mg/kg BW xylazine (Group 2). Premedication with 0.08 mg/kg BW romifidine without postanaesthetic sedation (Group 3) could be carried out at mean duration of anaesthesia of 85 minutes with no negative effects observed during the recovery period. Premedication with xylazine without postanaesthetic sedation (Group 1) is not to be recommended, as the number of attemps to stand up was significantly higher and coordination was either weak or significantly poorer than in the other three groups. The results of this study show that post-anaesthetic sedation of horses with an alpha 2-adrenoceptor agonist can improve the recovery phase after inhalant anaesthesia with isofluorane in regard to the number of attempts to arise and the animals' physical coordination.