ANSWERS

1. Why must particular care be taken with the anaesthesia of reptiles, amphibians, fish and invertebrates?
   These species are poikilothermic (or cold blooded) which means that they are unable to regulate their own body temperature. They are therefore particularly susceptible to hypothermia.
2. Why are small mammals such as rats and gerbils at risk from hypothermia?
   They have a large surface to volume ratio.
3. How might the risk of hypothermia be reduced during the anaesthesia of small mammals and exotics?
   • Operating in a warm ambient environment free from draughts.
   • Avoiding excess clipping of fur.
   • Avoid over-enthusiastic preparation of the surgical site which may result in the animal becoming wet.
   • Warm fluids prior to use.
   • Use incubators and heat pads during the surgical procedure and recovery.
   • Insulate the body of the animal with a proprietary material or bubble wrap if possible.
4. Which species must not be allowed to become too dry or hot, and should ideally be operated on wrapped in a damp cloth?
   Amphibians such as frogs, toads, newts and salamanders.
5. Describe an induction tank suitable for amphibians and fish.
   A container filled with a dilute solution of tricaine methane sulphonate or benzocaine. The container must be deep enough to immerse a fish, or to submerge an amphibian up to its nostrils. The container should not be too large (to discourage excess movement), heavy (to prevent it from being knocked over) and transparent (to enable close monitoring from all sides).
6. Describe an anaesthetic chamber.
   An anaesthetic chamber, provided it is secure and not causing a pollution risk, may be of a proprietary type or home-made. It consists of a transparent container with an inlet for a tube to transport the gas from the machine and an outlet for a scavenge tube. If the volatile agent is placed within the chamber on absorbent material, this should be located so that the animal cannot come into direct contact with it.
7. Why should the anaesthetic chamber be made of glass or transparent plastic?
   In order for the anaesthetist to observe the patient from all sides.
8. Why must care be taken if an anaesthetic chamber is made from materials other than glass?
   The volatile agent may react with or cause certain plastics to melt. Harmful fumes may be given off.
9. For what purpose might a canvas or cloth bag be employed during the anaesthesia of exotic species?
   • Restraint of small, wriggling animals and snakes for weighing.
   • Recovery bag for birds.
10. What duration of pre-anaesthetic fasting is recommended for the following species: (i) Ferrets. (ii) Granivorous birds. (iii) Waterfoul and carnivorous birds. (iv) Chelonians & lizards. (v) Snakes.
    • Ferrets - 12-16 hours.
    • Granivorous birds - rarely required, but never more than 3 hours.
    • Waterfowl & carnivorous birds - 4-10 hours.
    • Chelonians & lizards - 18 hours.
    • Snakes - 72-96 hours.
11. Why is it necessary to fast chelonians prior to anaesthesia?
    In order to avoid compression of the lungs.
12. Why is it necessary to fast snakes prior to anaesthesia?
    To prevent vomiting and the associated risk of aspiration pneumonia.
13. Name 2 species in which pre-anaesthetic fasting is unnecessary.
    • Lagomorphs (rabbits and hares).
    • Small rodents such as mice, hamsters and gerbils.
14. Why should small mammals and birds with a high metabolic rate not be fasted?
    They may suffer hypoglycaemia.
15. Small mammals and exotics are particularly prone to stress. List ways in which induction may be made less traumatic.
    • Acclimatisation of the animal to the handler/s and environment (although it is advised that physical contact is kept to a minimum).
    • Using a competent member of staff to restrain the animal to avoid escapees.
    • The use of premedicant drugs.
    • Avoiding the use of bright lights.
    • Working in a calm, quiet environment.
16. Why is it sensible to avoid placing birds and reptiles in dorsal recumbency whilst anaesthetised?
    The weight of the viscera on the lungs may reduce tidal volume (the quantity of gas inspired and expired in one breath) and cause respiratory embarrassment.
17. If an anaesthetic circuit is to be used, what would be the most suitable and why?
    The Ayres T piece, since it is suitable for animals weighing less than 10 kg (applicable for most exotics seen in practice) and has no valves meaning there is little resistance to breathing. The Jackson Rees modification means that IPPV may be performed if necessary.