Immersion and branchial/transcutaneous irrigation anaesthesia with alfaxalone in a Mexican axolotl

Immersion anaesthetic techniques are commonly used in amphibian species. Alfaxalone has been reported as an immersion anaesthetic in fish but not amphibians.

A Mexican 56 g axolotl was presented with a 3-day history of anorexia. Anaesthesia was required for the surgical retrieval of two gastric foreign bodies. Prior to anaesthesia, on visual inspection the axolotl was bright and active. Branchial and gular respiratory movements occurred at approximately 24 respirations minute(-1) and heart rate was approximately 52 beats minute(-1) .

The axolotl was exposed to increasing concentrations (up to 5 mg L(-1) ) of alfaxalone (Alfaxan; Vetóquinol, UK) in a water bath. After becoming sedated the axolotl was removed from the water bath. Anaesthesia was induced and maintained with alfaxalone (5 mg L(-1) ) via continuous irrigation of the gills (branchial) and skin (cutaneous) with additional 30 μL drops of alfaxalone (10 mg mL(-1) ) administered branchially as required. Endoscopy and surgery were performed to remove two gastric foreign bodies. Branchial and gular respiratory movements persisted at what was considered an appropriate anaesthetic depth. Anaesthetic depth could be rapidly deepened by branchial irrigation of alfaxalone solutions and lightened by irrigation using fresh water. Anaesthesia lasted approximately 1 hour and recovery was rapid (within 15 minutes). Recovery was assisted through branchial and cutaneous irrigation with fresh water.

No obvious adverse effects of anaesthesia were observed immediately post-anaesthesia or, according to the owner, in the following week. Conclusions  Axolotls can be anaesthetized using alfaxalone administered via immersion and branchial/transcutaneous irrigation offering an alternative technique for anaesthetising axolotls for clinical and research purposes.