Abstract

Alfaxalone (Alfaxan®, Jurox, London, UK, 10 mg/ml) is a rapid-acting, neurosteroid anesthetic that can be administered by intravenous or intramuscular injection. Alfaxalone is widely used throughout Europe, Australia, and Canada in a variety of domestic and exotic species.^2-8 Reported use in marine mammals is limited, with the most complete study to date having been done in free-ranging South American fur seals (Arctocephalus australis).¹

Anesthetic induction of California sea lions (Zalophus californianus) (n = 9) with alfaxalone (1.07–2.02 mg/kg) and midazolam (0.196–0.312 mg/kg) administered intramuscularly was performed opportunistically during assessments at a rehabilitation center. Mean and median times to initial effect were 3.22 min and 3.0 min, respectively. Mean and median times to recumbency were 5.22 min and 4.0 min, respectively. A deep plane of sedation adequate for non-stimulating procedures, including radiographs, ultrasound, and blood sampling, was achieved. Supplemental isoflurane was required for more invasive procedures (n = 6), such as oral surgery and wound debridement. Heart and respiratory rates remained within normal ranges. Mild to moderate hypoxia was noted in some cases (n = 2), but was quickly corrected with intubation and supplemental oxygen. Mild to moderate muscle fasciculation was commonly noted and exacerbated by auditory stimuli, but not tactile or visual stimuli. No other side effects were observed. Smooth recoveries from anesthesia were noted in cases antagonized with flumazenil (n = 5; 0.010–0.016 mg/kg IM).

Alfaxalone with midazolam appears to be a safe and reliable combination for anesthetic induction in California sea lions, and warrants further investigation. Additionally, this may be a favorable induction protocol for ophthalmic exams and procedures, as ventromedial rotation of the globe was minimal compared to other drug combinations.

Acknowledgements

The authors wish to thank the staff of the Marine Mammal Center, especially Dr. Greg Frankfurter and the veterinary staff. The authors thank the John G. Shedd Aquarium and the Marine Mammal Center for financial support of this project.

* Presenting author

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