Immersion Anesthetics in Freshwater Stingrays: Comparing the Effects of MS-222 and Alfaxalone on Potamotrygon sp.
Freshwater stingrays (Potamotrygon spp.) are becoming increasingly popular additions to home and institutional aquariums. Consequently, veterinarians may be asked to treat them when medical issues arise. The purpose of this study was to evaluate two different types of immersion anesthetics for freshwater stingrays and develop anesthetic protocols to safely accommodate them for examinations, diagnostic testing, and surgery. Eight juvenile stingrays were used for this crossover study. The average body weight for these animals was 61.2 g (minimum–maximum: 39.5–103.6 g). Two different commonly available anesthetics were used: tricaine methanesulfonate (MS-222) and alfaxalone. Stingrays were randomly assigned to two groups. Group 1 received MS-222 first, followed by alfaxalone, while group 2 received alfaxalone first, followed by MS-222. A 2-week wash-out period was used between trials. Baseline heart rate, respiration rate, and response to noxious stimuli were assessed prior to induction and every 3 minutes until the stingrays were recovered. Blood samples for blood gases were taken before induction (baseline), when a surgical level anesthesia was reached, and after full recovery. Average induction times were 2 minutes for MS-222 and 2.5 minutes for alfaxalone. Both anesthetics successfully anesthetized the stingrays to a level sufficient for surgical anesthesia, with full recoveries being achieved, on average, in 12 minutes for MS-222 and 24 minutes for alfaxalone. By comparing blood gas and electrolyte values, induction rates, response to noxious stimuli, and recovery times, we were able to determine that both anesthetics could be used safely in these animals.
The authors wish to thank Drs. Lois L. Hoyer, Jimmy Johnson, and Matt Allender for their contributions to the project. The authors would also like to thank the Merial Veterinary Scholars Program, Fluker Farms, and Sailfin Pet Shop for their support of the project.
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