Michelle Kischinowsky (KU-LIFE), Mads Bertelsen

Objective To characterise the clinical effects of alfaxalone by intramuscular (IM) injection in red-eared sliders (Trachemys scripta elegans) and to investigate the influence of body temperature on anaesthetic duration and depth as well as heart rate.

Study design Prospective, randomised half-blinded clinical trial.

Animals Ten adult female red-eared sliders.

Methods Alfaxalone was administered intramuscularly in both forelimbs. Each turtle was anaesthetised four times with the following protocol combinations of dosage and core body temperature: 10 mg kg^-1 at 20°C; 20 mg kg^-1at 20°C; 10 mg kg^-1 at 35°C and 20 mg kg^-1at 35°C.
Duration of time to maximal effect, plateau phase and recovery were recorded. Skeletal muscle tone of the neck, jaw, front and hind limbs, presence of palpebral, corneal and tap reflexes, presence of spontaneous movement, response to painful stimuli, and heart rate were recorded.

Results Mean time to maximal effect was 15.2±7.5, 19±6.2, 5.3±1.5 and 6.7±5.1 minutes 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. Duration of the plateau phase was 12.9±11.7, 27.5±13.4, 7.6±5.1 and 7.8±5.1 minutes, respectively. Recovery time was 76±20.4, 125.5±17.2, 28.1±9.4 and 41±19.5 minutes, respectively, and total anaesthetic duration was 104.5±21.8, 172±14.6, 41±8.4 and 55.5±18.2 minutes, respectively. Endotracheal intubation was successful in 80%, 100%, 0% and 30% of turtles, respectively.

With protocol 10 mg kg^-1 20°C, the loss of peripheral pain sensation in the front limbs, hind limbs and vent was 20%, 20% and 10%, respectively; whereas with protocol 20 mg kg^-1 20°C 40%, 20% and 20% lost pain sensation. At 35°C no animals lost pain sensation.

Corneal and tap reflexes were retained in all trials. Heart rates remained constant throughout anaesthesia, with mean values of 30±2.27 and 66±3.7 beats/min at 20° and 35°C, respectively.

Conclusions and clinical relevance Alfaxalone administered intramuscularly in healthy female red-eared sliders provided smooth and rapid induction and uneventful recovery. At 35°C either dosage provided only a short (5-10 minutes) and light sedation. At 20°C, 10 mg kg^-1 provided sedation suitable for short non-invasive procedures, such as clinical examination, blood and biopsy sampling etc. 20 mg kg^-1 provided anaesthesia with good muscle relaxation of approximately 20 minutes duration, appropriate for brief surgical procedures with appropriate supplemental analgesia, or for induction of inhalational anaesthesia.