Comparison of two formulations of alfaxalone for immersion anaesthesia in laboratory zebrafish (Daniorerio).

OBJECTIVE: To compare two commercial formulations of alfaxalone for immersion anaesthesia in laboratory zebrafish. STUDY DESIGN: Prospective, blinded, randomized study. ANIMALS: A total of 20 adult Danio rerio (Tuebingen strain). METHODS: Zebrafish were divided into two groups of 10 (five female, five male) and placed in individual immersion baths containing 10 mg L-1 of unpreserved alfaxalone (group 1) or preserved alfaxalone (group 2). Anaesthetists blinded to treatment used a composite score scale (CSS) (range 0-12) to assess fish every 30 seconds until induction of anaesthesia. Anaesthetic induction occurred when equilibrium and response to stimulus were lost. Fish were then placed in a clean water bath and scored every 60 seconds. Recovery from anaesthesia was defined as a CSS of ≤ 1. Time variables recorded were anaesthetic induction time (AIT), anaesthetic recovery time (ART) and total procedure time (TPT). Fish were observed for evidence of roupgross external pathology during the procedure. Following anaesthesia, four fish from each group were randomly chosen and euthanized for gill histopathology analysis immediately after recovery criteria were met. Data are presented as mean ± standard deviation. An independent t test was used to compare the difference in average anaesthetic time variables between groups (α = 0.05). RESULTS: There were no statistical differences between groups in reported variables. TPT, AIT and ART were 10.2 ± 1.2, 1.9 ± 0.9 and 8.3 ± 1.2 minutes for group 1 and 10.8 ± 2.9, 2.4 ± 1.2 and 8.4 ± 2.7 minutes for group 2. No gross external pathology was evident, and no fish died during the experimental period. Histopathology showed normal gill pathology and no difference between the groups. CONCLUSIONS AND CLINICAL RELEVANCE: Immersion anaesthesia using 10 mg L-1 of either formulation of alfaxalone resulted in anaesthesia of similar quality and duration.

Total Intravenous Anaesthesia with Ketamine, Medetomidine and Midazolam as Part of a Balanced Anaesthesia Technique in Horses Undergoing Castration.

To evaluate the use of ketamine-medetomidine-midazolam total intravenous infusion as part of a balanced anaesthetic technique for surgical castration in horses. Five healthy Standardbred cross colts were premedicated with IV acepromazine (0.01-0.02 mg/kg), medetomidine (7 µg/kg) and methadone (0.1 mg/kg) and anaesthesia induced with IV ketamine (2.2 mg/kg) and midazolam (0.06 mg/kg). Horses were anaesthetised for 40 min with an IV infusion of ketamine (3 mg/kg/h), medetomidine (5 µg/kg/h) and midazolam (0.1 mg/kg/h) while routine surgical castration was performed. Cardiorespiratory variables, arterial blood gases, and anaesthetic depth were assessed at 5 to 10 min intervals. Post-anaesthesia recovery times were recorded, and the quality of the recovery period was assessed. The anaesthetic period and surgical conditions were acceptable with good muscle relaxation and no additional anaesthetic required. The median (range) time from cessation of the infusion to endotracheal tube extubation, head lift and sternal recumbency were 17.2 (7-35) min, 25 (18.9-53) min and 28.1 (23-54) min, respectively. The quality of anaesthetic recovery was good, with horses standing 31.9 (28-61) min after the infusion was ceased. During anaesthesia, physiological variables, presented as a range of median values for each time point were: heart rate 37-44 beats/min, mean arterial pressure 107-119 mmHg, respiratory rate 6-13 breaths/min, arterial partial pressure of oxygen 88-126 mmHg, arterial partial pressure of carbon dioxide 52-57 mmHg and pH 7.36-7.39. In conclusion, the co-administration of midazolam, ketamine and medetomidine as in IV infusion, when used as part of a balanced anaesthetic technique, was suitable for short term anaesthesia in horses undergoing castration.