COMPARISON OF ISOFLURANE AND ALFAXALONE (ALFAXAN) FOR THE INDUCTION OF ANESTHESIA IN FLAMINGOS (PHOENICOPTERUS ROSEUS) UNDERGOING ORTHOPEDIC SURGERY

Abstract

Used since the 1970s as an avian anesthetic, the neurosteroid alfaxalone has been reformulated to avoid side effects from its castor oil excipient. This case report describes the clinical use of a new alfaxalone formulation (Alfaxan) as an intravenous anesthetic induction agent in wild isoflurane-anesthetized rose flamingos (Phoenicopterus roseus). Twenty-five male and female rose flamingos underwent orthopedic surgery using isoflurane anesthesia. The animals were induced following one of two protocols: inhaled isoflurane by facemask (ISO; n = 9) or intravenous alfaxalone (2 mg/kg; ALF; n = 16). The time and quality of anesthetic induction (until first signs of muscle relaxation) and the time and quality of recovery (sternal recumbency) were recorded using a scoring system. Mild sedation was first observed at 18.4 +/- 3.8 min and 1.7 +/- 0.3 min, following isoflurane and alfaxalone administration, respectively (P < 0.001). Alfaxalone induction time was significantly shorter and induction quality was considered smoother than in the ISO group. Flamingos given alfaxalone induction required lower isoflurane concentrations for maintenance anesthesia than did flamingos induced with mask isoflurane (1.5-2 % vol vs. 4-5 % vol for ALF vs. ISO, respectively). Alfaxalone produced moderate cardiorespiratory effects not seen in the isoflurane induction group. Recovery times were similar with both protocols without significant differences in quality and length. The new alfaxalone formulation produces a safe and effective anesthetic induction in rose flamingos and has significant isoflurane-sparing effects during anesthesia.

Pharmacokinetics and pharmacodynamics of alfaxalone after a single intramuscular or intravascular injection in mallard ducks (Anas platyrhynchos)

“…Intramuscular administration of alfaxalone did not provide a deeper level of sedation but was associated with a prolonged recovery with smoother characteristics than IV administration. Both IV and IM results were not consistent with the level of sedation and/or anesthesia achieved in other studies that used different species; with very few reports on alfaxalone pharmacodynamics in avian species (Balko et al, ; Cullen et al, ; Curtis, Jemmett, & Hendy, ; Perrin et al, ; Villaverde‐Morcillo et al, ). We are unsure as to why the ducks did not obtain deeper levels of anesthesia, but another consideration is the amount of stress during manual handling.…”

“…The majority of those birds (83%) receiving 10 mg/ kg IM lost righting reflex, but all of them responded to a noxious stimulus (Balko et al, 2017). Stable heart rates and a lack of apnea observed in these mallard ducks have been reported in other avian species at different doses of alfaxalone, but different routes of administration, volume, or addition of other anesthetic agents could have led to slower absorption and most likely the reason for the lack of apnea detected (Cullen et al, 1995;Curtis et al, 1977;Villaverde-Morcillo et al, 2014). Unlike the mallard ducks in this study, Bengalese finches exhibited gradual, progressive clinical signs of sedation prior to recumbency, and longer anesthetic duration .…”

“…However, inhalant anesthesia may not be practical in certain field conditions dictating the need for a safe and effective injectable anesthetic protocol. Alfaxalone is a synthetic, neuroactive, hydrophobic steroid that has been used to induce and maintain short‐term anesthesia in several avian and wildlife species (Adami, Spadavecchia, Angeli, & d'Ovidio, ; Bertelsen & Sauer, ; Cooper & Frank, ; Cooper & Redig, ; Cullen et al, ; Goodwin et al, ; Holt, ; Lau et al, ; Phillips, Posner, Lewbart, Christiansen, & Harms, ; Shepherd, Divers, Braun, & Hofmeister, ; Villaverde‐Morcillo, Benito, García‐Sánchez, Martín‐Jurado, & Segura, ). While it does not result in analgesia, it has been documented to have decreased cardiopulmonary side effects compared to other agents that can be administered intramuscularly, except in the bullfrog ( Lithobates catesbeianus ) after IV administration (Ennis & Lorenz, ; Williams et al, ).…”

“…Currently, reports have demonstrated effective use of alfaxalone with other anesthetic agents in ostriches ( Struthio camelus ) (Cullen et al, ). The sedative effects of alfaxalone were evaluated in Bengalese finch, cranes, flamingos ( Phoenicopterus roseus ), and mute swans ( Cygnus olor ) (Bailey, Toosi, & Samour, ; Baldrey, ; Perrin et al, ; Villaverde‐Morcillo et al, ). Dosages for multiple field reports and studies have been extrapolated from other published references, but the safety margin of alfaxalone in avian species has not been determined (Bailey et al, ; Baldrey, ; Punch, ; Smith & Rodriquez‐Barbon, ).…”

“…Overall, studies of alfaxalone used in avian species are limited with no known pharmacokinetic reports and very few pharmacodynamic ones (Perrin, Nielsen, Thomsen, & Bertelsen, 2017;Villaverde-Morcillo et al, 2014). Currently, reports have demonstrated effective use of alfaxalone with other anesthetic agents in ostriches (Struthio camelus) (Cullen et al, 1995).…”