EFFECTIVENESS OF ALFAXALONE AS AN ANAESTHETIC IN REPTILES

Lowland Copperhead (Austrelaps superbus)

Chemical restraint (i.e. anaesthesia) is often needed to facilitate clinical examination and surgery in captive reptiles. However, several chemical agents commonly used in reptiles often have undesirable side-effects such as prolonged recovery and respiratory depression.

Alfaxalone is a relatively new anaesthetic agent for reptiles, but has been used in small animal medicine in Australia and New Zealand for a number of years. Many clinicians prefer alfaxalone because it clears rapidly and is metabolised independently of organ function; animals also have a smooth and rapid recovery, and suppression of the cardiovascular system is minimal.

Anecdotally, the use of alfaxalone in reptiles has resulted in favourable results.  Dr Franciscus Scheelings and other Healesville Sanctuary vets conducted a preliminary trial of its use in reptiles.

AIM

To assess the effects and suitability of alfaxalone as an anaesthetic induction agent for reptiles.

METHODS

Healthy snakes and lizards from the Healesville Sanctuary collection were used in this preliminary study. More than thirty animals were tested from the following species:

Reptiles are ectothermic and environmental temperature can affect metabolic rate and response to anesthetic agents. Therefore all reptiles were placed into an intensive care unit at 30-35°C for one hour prior to induction of anesthesia.

Each individual was then manually restrained and injected intravenously into the coccygeal vein with 9mg/kg alfaxalone (Alfaxan®-CD RTU 10mg/ml, Jurox Pty. Ltd. Rutherford, NSW). Following injection, all animals were maintained on a warm air blanket (38°C) for the duration of the study.

Reactions were recorded on a standard anesthetic chart. Induction time was defined as the time from injection to the loss of the righting reflex. Once induced, all animals were intubated and maintained on room air. Heart rate (using Doppler unit), respiratory rate and temperature were measured every five minutes. Depth of anesthesia was assessed at five-minute intervals using righting reflex, response to noxious stimuli (pinching the vent and tongue withdrawal reflex in snakes and toe pinch in lizards). No response to pinching the vent or toes was considered indicative of a plane of surgical anesthesia (Bennett 1991).

Animals were judged to have recovered from anesthesia once spontaneous movement and righting reflex had returned.

RESULTS

Intravenous administration of alfaxalone only resulted in mild sedation in blotched bluetongue lizards and did not permit intubation. However, in all other species examined, intravenous alfaxalone resulted in immediate induction with a signficant period of anesthesia, and intubation was possible. A surgical plane of anesthesia was not achieved in any species (withdrawal reflexes persisted) but spontaneous respiration was maintained in all animals examined.

PROJECT OUTCOMES

Intravenous alfaxalone at a dose of 9mg/kg appears to be a safe and effective induction agent in a variety of squamate reptiles. Further research is required for its use in blotched bluetongue lizards.

FOR MORE INFORMATION

- on this research project - click here to email Dr Franciscus Scheelings (Principal Investigator)