CARDIOVASCULAR EFFECTS OF ALFAXALONE AND PROPOFOL IN THE BULLFROG, LITHOBATES CATESBEIANUS

Alfaxalone is becoming a popular anesthetic for nonmammalian vertebrates, but the physiological effects of its administration remain largely unknown in these taxa. Therefore, the cardiovascular responses to a clinically relevant dose of alfaxalone (10 mg/kg) are reported in the bullfrog ( Lithobates catesbeianus), following intramuscular (IM) and intravascular (IV) administration (via a femoral artery catheter) and compared with an IV dose of propofol, another parenteral GABA (γ-aminobutyric acid) agonist in common veterinary use as an induction agent. Heart rate (HR) and mean arterial blood pressure (MAP) (assessed by direct measurement from the catheter) are reported from under undisturbed conditions to assess both the direct effects of the drugs and the interaction with the stress of handling associated with IM injection of alfaxalone where IM administration is possible. Alfaxalone caused HR to increase significantly for over 45 min in both groups from a baseline of approximately 30 beats/min. This was significantly different from the lack of significant HR response on the IV administration of propofol. MAP increased in the peri-injection period with both routes of administration for alfaxalone but after IV use decreased significantly from 10 min following administration. Propofol did not affect blood pressure after 5 min from injection. Assessment of immobilization following intramuscular injection of alfaxalone in a pilot study was in accordance with the literature, as it provided no antinociception as a sole agent but did produce sedation and loss of righting reflex.