ALFAXALONE AS AN INTRAMUSCULAR INJECTABLE ANESTHETIC IN KOI CARP (CYPRINUS CARPIO)

Abstract

Fish are commonly anesthetized with MS-222 (tricaine methanesulfonate), a sodium-channel-blocker used as an immersion anesthetic, but its mechanism of action as a general anesthetic is uncertain. Alfaxalone is a neurosteroid that acts at the GABA(A) receptors. Alfaxalone has been evaluated and was deemed successful as an immersion agent in koi carp. Alfaxalone is an effective intramuscular anesthetic in multiple species. A reliable intramuscular anesthetic in fish would be useful in multiple settings. The purpose of this study was to investigate alfaxalone as an intramuscular injectable anesthetic agent in koi carp (Cyprinus carpio). Eight koi carp were utilized in a crossover design. In each trial, six fish received 1 mg/kg, 5 mg/kg, or 10mg/kg of alfaxalone intramuscularly. They were assessed every 15 min for opercular rate and sedation score. The sedation score was based on a visual scale from 0 to 5, 0 indicating no response and 5 indicating absent righting reflex and anesthesia. Anesthetized koi were placed on a fish anesthesia delivery system (FADS). Time to anesthesia/recovery was recorded and heart rate was recorded every 15 min. Anesthesia was achieved in 0/6, 1/6, and 5/6 fish at 1, 5, and 10 mg/kg, respectively. Duration of anesthesia for one fish at 5 mg/kg was 2 hr. At 10 mg/kg, median anesthesia duration was 6.5 (3-10) hr. At 10 mg/kg, prolonged apnea (2-3 hr) was observed in 3/6 fish, 2/3 died under anesthesia, and 1/3 recovered 10 hr post-injection. Median peak sedation scores were 1.5, 2.5, and 5, at 1, 5, and 10 mg/kg, respectively. A dosage of 10 mg/kg alfaxalone resulted in 33% mortality. The duration of anesthesia and opercular rate were unpredictable. Due to variation in response despite consistent conditions, as well as risk of mortality, intramuscular alfaxalone cannot be recommended for anesthesia in koi carp.

Effect of water temperature on the anesthetic effects of alfaxalone in carp (Cyprinus carpio)

“…The carp used in this study were considered to be able to maintain their HR, even with a short-term decrease in water temperature due to heat tolerance, and no significant change was observed during the study period compared to normal water temperature. Moreover, alfaxalone administration did not lead to any significant changes in HR or significant differences between water temperature groups at any time point, corroborating the findings by Bailey et al [ 7 ].…”

“…Although there are few reports of alfaxalone intramuscular administration in carp, Bailey et al [ 7 ] reported lethal side effects such as respiratory arrest upon intramuscular administration of 10 mg/kg alfaxalone in carp. In this study, the risk of apnea was predicted, but respiratory depression due to alfaxalone administration was not confirmed.…”

“…With intramuscular administration, it is possible to reliably administer a small dose of anesthetic, which is more economical. When alfaxalone was previously intramuscularly administered to carp at 1, 5, or 10 mg/kg, only 10 mg/kg displayed a sufficient anesthetic effect [ 7 ]. However, at a dose of 10 mg/kg, a mortality rate of 33% was recorded, concluding that intramuscular alfaxalone administration in carp was risky and thus not recommended.…”

“…Alfaxalone is an anesthetic agent widely used in both mammals and reptiles and is commonly used to induce anesthesia in veterinary medicine [ 1 – 5 ]. However, a high mortality rate due to an overdose of alfaxalone injection anesthesia was known, and only immersion anesthesia is acceptable [ 6 , 7 ]. Therefore, the dose of alfaxalone should be kept in a low and manageable range, although this may not provide a sufficient anesthetic effect.…”

The Effectiveness of Ketamine as an Anesthetic for Fish (Rainbow Trout – Oncorhynchus mykiss)

“…Anesthetics are necessary for reducing stress and strife in fish for a variety of activities ranging from transporting to surgical operations also it is important for sampling [1][2][3], egg extraction (artificial reproduction), drug or vaccine injection, physical examination, blood sampling, biopsy, or biometry for aquatic animals. The efficiency, safety and harm of anesthetics compound depend on fish species, fish size, physicochemical properties of water (water quality), environmental factors (temperature), type of anesthetic drug and drug delivery method [4][5][6].…”