Objective To determine the minimum infusion rate (MIR) of alfaxalone required to prevent purposeful movement of the extremities in response to noxious stimulation. Study Design Prospective, experimental.Animals Eight healthy goats; four does and four wethers.Methods Anaesthesia was induced with alfaxalone 3 mg kg -1 intravenously (IV). A continuous IV infusion of alfaxalone, initially at 0.2 mg kg -1 minute -1 , was initiated. Following endotracheal intubation the goats breathed spontaneously via a circle breathing circuit delivering supplementary oxygen. The initial infusion rate was maintained for 30 minutes before testing for responses. The stimulus was clamping on the proximal (soft) part of one digit of the hoof with Vulsellum forceps for 60 seconds. In the absence or 2 presence of purposeful movement of the extremities, the infusion rate was reduced or increased by 0.02 mg kg -1 minute -1 and held constant for 30 minutes before claw-clamping again. Alfaxalone MIR was calculated as the mean of the infusion rates that allowed and abolished movement. Cardio-respiratory parameters were measured. Recovery from general anaesthesia was timed and quality scored. Results are presented as median (range). ResultsThe MIR of alfaxalone was 0.16 (0.14-0.18) mg kg -1 minute -1 or 9.6 (8.4-10.8) mg kg -1 hour -1 .Induction of and recovery from anaesthesia were excitement-free. Cardio-respiratory changes were minimal, although compared to baseline HR increased, and at 2 minutes post-induction, (prior to oxygen supplementation), P a O 2 decreased significantly from 84 (80-88) to 70 (51-72) mmHg (11.2 (10.7-11.7) to 70(51-72) mmHg (9.3 (6.8-9.6) kPa). Sporadic muscle twitches, unrelated to depth of anaesthesia, were observed during the period of general anaesthesia. Time (minutes) to sternal recumbency and standing were 4.0 (3.0-10.0) and 41.5 (25.0-57.0) respectively. Conclusions and Clinical RelevanceAlfaxalone can be used for total intravenous anaesthesia (TIVA) in goats and is associated with minimal adverse effects. Oxygen supplementation is recommended.

IntroductionThe minimum infusion rate (MIR) of alfaxalone when co-administered with midazolam in goats was evaluated.Materials and methodsEight goats (four does and four wethers) were anaesthetised, on separate occasions, with alfaxalone at an initial dose of 9.6 mg/kg/hour combined with one of three midazolam treatments: a bolus of 0.1 mg/kg followed by constant rate infusion (CRI) of 0.1 mg/kg/hour (treatment LMID), 0.3 mg/kg followed by CRI of 0.3 mg/kg/hour (MMID), 0.9 mg/kg followed by CRI of 0.9 mg/kg/hour (HMID), intravenously. Responses to stimulation (clamping on the proximal part of one digit of the hoof with Vulsellum forceps for 60 seconds) were tested every 30 minutes. In the absence or presence of a response to stimulation, the infusion rate was reduced or increased by 1.9 mg/kg/hour. Alfaxalone MIR was calculated as the mean of the infusion rates that allowed and abolished movement. Cardiopulmonary parameters were measured.ResultsAlfaxalone MIR was 6.7 (6.7–8.6) mg/kg/hour, 6.7 (4.8–6.7) mg/kg/hour and 2.9 (1.0–4.8) mg/kg/hour for LMID, MMID and HMID respectively. Cardiopulmonary function was minimally affected, with hypoxaemia observed two minutes into anaesthesia during all treatments. Recovery from anaesthesia was excitement-free.ConclusionsMidazolam causes a dose-dependent reduction of alfaxalone MIR in goats. Oxygen supplementation is recommended during anaesthesia with alfaxalone and midazolam in goats.