Abstract

Alfaxalone is a neurosteroid anesthetic that has been utilized as an induction agent in a variety of species, including fish. While parenteral anesthetic agents are used in fish, immersion anesthetics are more commonly used. Of these, tricaine methanesulfonate is the most popular immersion anesthetic; however, it is not as readily available at this time because a major distributor is no longer offering it for sale. The objective of this study was to evaluate the efficacy of alfaxalone as an immersion anesthetic in Oscar fish (Astronotus ocellatus), a popular cichlid amongst aquarium enthusiasts, and its effect on physiologic and blood gas parameters in this species. The study design was a prospective experimental trial. Six Oscar fish, examined and found to be healthy, were individually immersed in water with 5 mg/L (5 ppm) alfaxalone. The water temperature was maintained between 23.9–26.7°C and water quality parameters were appropriate for this species. During the anesthetic trial, fish were monitored for anesthetic plane based on a defined ordinal scale, opercular rate, heart rate, response to noxious stimuli, and blood gas values at baseline (pre-immersion), surgical anesthetic depth, and at recovery. Alfaxalone at 5 mg/L was sufficient to induce anesthesia for diagnostic sampling in the Oscar fish. Median lactate was significantly increased (p<0.05) in all fish that were anesthetized. Median P_CO2 was also found to be increased but was not statistically significant (p=0.07). No other significant differences were noted in the physiologic or blood gas parameters that were measured.