Intramuscular administration of alfaxalone in red-eared sliders (Trachemys scripta elegans) – effects of dose and body temperature

To characterise the effects of alfaxalone by intramuscular (IM) injection in red-eared slider turtles and the influence of body temperature on anaesthetic duration and depth. Prospective, randomised part-blinded experimental trial. Ten healthy adult female red-eared sliders. Each turtle was anaesthetized four times with 10 and 20 mg kg−1 alfaxalone at 20 and 35 °C respectively. Time to maximal effect and plateau and recovery periods were recorded. Skeletal muscle tone, presence of various reflexes, response to noxious stimuli, and heart rate were assessed. Results are given for protocols 10 mg kg−1 20 °C; 20 mg kg−1 20 °C; 10 mg kg−1 35 °C and 20 mg kg−1 35 °C, respectively: mean time (±SD) to maximal effect was 16 ± 8, 19 ± 6, 5 ± 2 and 7 ± 5 minutes; duration of the plateau phase was 13 ± 12, 28 ± 13, 8 ± 5 and 8 ± 5 minutes and recovery time was 76 ± 20, 126 ± 17, 28 ± 9 and 41 ± 20 minutes. Endotracheal intubation was successful in 80%, 100%, 0% and 30% of turtles, respectively. At 35 °C, all animals retained nociceptive sensation in the front limbs, hind limbs and vent, whereas at 20 °C a few turtles lost peripheral nociceptive sensation. Corneal and tap reflexes were retained in all trials. Mean heart rates were 30 ± 2 and 66 ± 4 beats minute−1 at 20 and 35 °C, respectively. Alfaxalone administered IM in red-eared sliders provided smooth, rapid induction and uneventful recovery. At 35 °C either dosage provided only short (5–10 minutes) and light sedation. At 20 °C, 10 mg kg−1 provided sedation suitable for short non-invasive procedures. About 20 mg kg−1 provided anaesthesia of approximately 20 minutes duration, appropriate for induction of inhalational anaesthesia or for brief surgical procedures with supplemental analgesia.