Objective To characterise the anaesthetic effects of alfaxalone administered intramuscularly (IM) at 10, 20, and 30 mg kg−1.
Study design Prospective, randomized cross-over study.
Animals Ten juvenile green iguanas (Iguana iguana) of mean body weight (±SD) 480 ± 134 g.
Methods Alfaxalone was administered IM in the triceps of both thoracic limbs. Times for anaesthetic induction, plateau and recovery periods were recorded. Skeletal muscle tone of the jaw, neck, thoracic limbs, pelvic limbs, and tail was scored. The palpebral, corneal and righting reflexes, and the response to painful stimuli were also assessed. Pulse rate and respiratory rate were recorded. Comparisons between different dosages and over time were made using anova.
Results Times are given for 10, 20 and 30 mg kg−1 dosages respectively: mean time to maximal effect was 7.7 ± 2.2, 5.4 ± 1.7 and 3.9 ± 1.2 minutes; duration of the plateau phase was 11.3 ± 3.8, 22.1 ± 6.5 and 39.1 ± 11.5 minutes; recovery time was 10 ± 2.4, 17.5 ± 8.6 and 25 ± 7.1 minutes; and total anaesthetic duration was 29 ± 35.7, 45 ± 8.2 and 68 ± 9.8 minutes. Endotracheal intubation was possible in 40% of the subjects given 10 mg kg−1 and in 100% subjects given both 20 and 30 mg kg−1. Loss of response to a painful stimulus was seen in 0/10, 8/10 and 9/10 animals at 10, 20, and 30 mg kg−1 respectively. There was an initial dose-dependent depression of respiration followed by a significant increase in frequency over time. In contrast, pulse rates decreased by 20% over the duration of the anaesthetic events.
Conclusions and clinical relevance Intramuscular administration of alfaxalone is a simple, rapid and reliable means of achieving relatively brief sedation or anaesthesia in healthy green iguanas. A dosage of 10 mg kg−1 provides light sedation, appropriate for examination and venipuncture; 20 mg kg−1 provides a level suitable for minor procedures or for endotracheal intubation and supplementation with inhalational anaesthesia; 30 mg kg−1 produces an anaesthetic plane suitable for surgical procedures of limited duration (up to 40 minutes).