Abstract
Alfaxalone is a rapid-acting neurosteroid that produces anesthesia in a variety of domestic and exotic species. The use of alfaxalone in marine mammals is limited and restrictive due to the large drug volume required for intramuscular injection. A concentrated version of alfaxalone (40 mg/ml) was made available by the manufacturer (Jurox Pty Ltd [Zoetis]) and used for premedication prior to anesthesia induction with isoflurane and oxygen in two New Zealand fur seals (Arctocephalus forsteri), two Californian sea lions (Zalophus californianus), and two Australian sea lions (Neophoca cinerea) undergoing lensectomy surgery.
Alfaxalone 4% (0.5–1 mg/kg) was combined with midazolam (50 mg/ml; 0.25 mg/kg) and pethidine (50 mg/ml; 2.0 mg/kg) in the same syringe and administered intramuscularly. Additional supplemental alfaxalone and midazolam were administered intramuscularly in one animal to achieve immobilization. Patient monitoring and anesthetic variables were monitored and documented for each animal including arterial blood pressure in three animals. Supplemental isoflurane in oxygen was administered via mask prior to intubation of all animals and general anesthesia was maintained on sevoflurane and oxygen.
Anesthetic induction time to intubation for the six animals was 5 to 45 minutes (range) (mean, 27 minutes). Alfaxalone administered at 0.5 mg/kg intramuscularly resulted in delayed and variable onset of sedation in the first three animals; therefore, the alfaxalone dose was increased to 1 mg/kg. Physiological parameters were within normal limits for each animal except for hypotension (n=1) and bradycardia (n=1). Duration of anesthesia ranged from 234 to 301 minutes (mean time, 287 minutes). Recovery times defined as time isoflurane off to extubation, standing, and spontaneously breathing ranged from 25 to 61 minutes (mean, 26 minutes). No injection pain or injection site reactions were observed in any animal. In conclusion, the intramuscular administration of alfaxalone 4% in combination with midazolam and pethidine provided good sedation prior to anesthetic induction with isoflurane.
*Presenting author