Intro to Exotics Anaesthesia

Question 1

Why is anaesthetic risk higher in exotic spp. than in dogs and cats? – general.

Answer 1

May be carried out sparsely so lack of familiarity.
May come into practice w/o clinical history so no knowledge if any pre-existing disease – some of these spp. good at hiding disease.
Financials – ‘pocket money pets’ – owners less likely to want to accept pre-GA bloods or imaging.

Question 2

Why is anaesthetic risk higher in exotic pets? – anatomical.

Answer 2

Size
- Difficult to obtain accurate weight.
- Difficult to examine/auscultate.
- IV access can be impossible.
- May have completely different anatomy. (no diaphragm, renal portal system, air sacs etc.)

Can be dangerous i.e. handling.
Stress of handling.
Lack of ‘standard’ equipment. (small enough BP cuffs, IV catheters).

Question 3

1. Risk with exotic patient eyes.
2. Pharyngeal pouches.

Answer 3

1. Some spp. have protuberant eyes.
   Risk of damage on mask or with patient positioning.
   Damage corneal surface.
2. Guinea pigs have these.
   They can hold green fluid which is unpleasant.
   Be aware if trying to intubate.

Question 4

Mouth anatomy.

Answer 4

Dentition
- Large incisors.
- Narrow jaw.
- Limited gape.
- Pharyngeal tissue in excess.
- Obstructive.
Impact on ability to intubate.

Question 5

Physiology as an impacting factor on anaesthetic in exotics.

Answer 5

High metabolic rate.
High consumption of glucose.
High consumption of O2.
- Increased risk of hypoglycaemia.

High SA : vol ratio.
High rate of heat loss.
At risk of hypothermia.

Question 6

1. Respiratory system.
2. CV system.

Answer 6

1. May be obligate nasal breathers (rabbits).
   May have pre-existing respiratory disease.
   Difficult to detect changes w/ auscultation.
2. Size of vessels.
   High HR.
   Affect monitoring.

Question 7

GI tract.

Answer 7

Carnivore vs herbivore.

e.g.

rabbit = herbivore, hindgut fermenter, large guts, reduced motility = problem!

Ferret = carnivore, simple stomach.

Question 8

Spp.-specific concerns.

Answer 8

• Disease / problem.
• Species predispositions.
  – Hyper-oestrogenism – ferret.
  – Liver torsion – rabbit.
• Drug concerns (licensing and availability).
• Poor husbandry – lack of knowledge re normal habitat.
• Lack of familiarity.
• Lack of specialist housing facilities i.e. vivarium.

Question 9

Special considerations for birds.

Answer 9

Wide range of spp.
Hide illness well.
Stress of restraint.
Danger to handler (claws, wings, beak etc).
Hypothermia.
Hypoglycaemia.
Weigh accurately.

Question 10

Bird considerations – resp.

Answer 10

Separate conducting and gas exchange areas.
Air sacs.
Efficient gas exchange – movement of sternum essential for breathing – need correct restraint.
Complete tracheal rings - Do not cuff!
Tracheal intubation possible in birds >100g.
Birds active inhalers AND expirers so muscle relaxants will affect ventilation much more.
Breathing controlled by small movements of intercostal and abdominal muscles.

Question 11

1. Birds special considerations – CV system.
2. GI.

Answer 11

1. Birds have a larger heart and greater CO so lower HR.
   High metabolic rate.
2. No fasting in birds that are <100g.
   Starvation dependent on size and spp is recommended by some.
   Crop may need emptying to prevent regurgitation.

Question 12

Special considerations for reptiles/snakes.

Answer 12

Common = tortoises, iguanas, terrapins, snakes.
Zoonotic risk – good hand hygiene etc.
Husbandry – humidity, UV light.
Poikilothermic or ectothermic – metabolic rate determined by ability to thermoregulate (derive body heat from external environment).

Question 13

Snake and reptiles special considerations – resp.

Answer 13

Fleshy tongue and long soft palate to be aware of during intubation.
No diaphragm – breathing ctrld by small movements of intercostal, pectoral and abdominal muscles +/- limb movements – do not restrict this during GA.
Breath holding.
Larynx only open during active respiration.
Lose moisture via the respiratory tract.
Reptiles have a lower O2 consumption compared to companion animals.
Most snakes have a single functional ‘right’ lung and not a pair.
Avoid cuffed ETT – many spp. have complete tracheal rings.

Question 14

1. Reptiles/snakes special considerations – CV system.
2. Snake eyes.

Answer 14

1. Many reptiles have 3 chambered heart w/ specialised shunting system to separate oxygenated and deoxygenated blood. Allows blood to bypass the lungs if required (i.e. periods of apnoea).
   Heart and organs can move freely.
2. Snakes do not have eyelids.

Question 15

1. Chelonians special considerations – resp.
2. ” “ – drugs.
3. ” “ – CV system.

Answer 15

1. Gas movement in and out of resp system produced by muscle movement of the limbs so can observe resp by watching the limbs move.
   Trachea bifurcates partially cranially so a shorter ETT used.
   Tortoises lack a diaphragm.
2. Thermoregulation will affect drug uptake, absorption and distribution.
3. Tend to have the lowest MAP (15-30mmHg).

Question 16

Pre-op fasting….
1. Rabbits.
2. G pigs.
3. Ferrets.
4. Snakes/reptiles.
5. Birds.
6. Tortoise.

Answer 16

1. NO fasting!
2. 0-4hrs prior – ensure swab out mouth before attempt intubation.
3. 6hrs prior.
4. Regurgitation not usually a problem.
   Avoid feeding live insects before anaesthesia.
5. Varies between spp.
6. Avoid live insects pre-GA.

** exotics often present w/ anorexia.

Question 17

Equipment needs for exotic GA.

Answer 17

Breathing systems (T-Piece, Bain, Circle, Lack, mini lack).
Gas chamber/induction box.
- Sometimes the only option.
- Must be justified.
- Unpleasant experience.
- Use suitable size container.
- Must have an input and an output.
- Consider health and safety.

Question 18

1. Which volatile agent may be more pleasant to use for gaseous inductions and why?
2. Consideration for gaseous induction of exotic spp.

Answer 18

1. Sevoflurane – less irritant to tissues / lower blood solubility so quicker effects seen.
2. Some spp. breath hold so may not be easy in all spp.

Question 19

Exotic spp. airway devices for airway management.

Answer 19

ETT.
Mask.
V-Gel.

Question 20

1. Sites of IV drug administration in birds.
2. Site of IM drug administration in birds.
3. Other routes of admin in birds.

Answer 20

1. Basilic vein, medial tarsal, right jugular.
2. Pectoral.
3. Intraperitoneal, subcutaneous, intraosseous (cranial tibiotarsus or ulna), inhalational (mask vs chamber), oral (liquid/tabs).

Question 21

Considerations for drug admin routes in some exotic spp.

Answer 21

Some susceptible to abscessation and septicaemia.
- Aseptic preparation.
- Massage site after SC injection.
- Pain on injection.

Question 22

Reflexes to check and look out for when monitoring exotic spp under GA.

Answer 22

• Righting reflex = initiated by vestibular system and detects that the body is not upright / normal position and will cause the head to move back to original position w/ rest of body following.
• Withdrawal reflexes.
• Jaw tone.
• Pinch reflex (toe, nail).
• Palpebral reflex.

Question 23

Vitals to monitor during GA in exotics.

Answer 23

Pulses – rate, bounding, weak, thready.
- Difficult in smaller animals.
– Medial aspect carpus in rabbit.
Temperature.
Ventilation - may need to assist w/ by IPPV.
Multiparameters.
- BP, capnography, ECG, pulse ox.
- ensure can count up to and over 200bpm.

Question 24

1. Sites for pulse ox attachment in exotics.
2. Considerations for capnography in exotics.

Answer 24

1. tongue may be too small so foot or tail base.
2. minimise dead space by using smaller adaptor.
   Consider sampling rate.

Question 25

ECG in exotics.

Answer 25

Ensure can count high rates.
Cut down pads.
– ferrets / rats - on pad of foot.
– consider clipping metacarpal/tarsal for rabbits.
Crocodile clips may be too harsh.
– consider needle electrodes for reptiles.
–> sub cut hypodermic needle w/ croc clip attached.

Question 26

BP in exotic patients.

Answer 26

Doppler.
- Shown to be a good indicator of arterial BP in rabbits.
- Can use on a variety of spp.
- Audible indicator of CO (pulse/ apex beat).
Direct BP.
- Carotid, femoral or tail.
- Usually done in research settings.
- Auricular useful in rabbits.

Question 27

Temperature monitoring in exotic patients.

Answer 27

Rectal more useful and accessible than mouth.
Care w/ probe size.

Question 28

What is the doppler stethoscope technique.

Answer 28

Doppler probe can be placed over the heart to give an audible HR.
- Place on apex beat for snakes.
- Place at the thoracic inlet or on the plastron at the junction between the pectoral and abdominal scutes (in smaller spp.) for chelonians.
- Place at the thoracic inlet, over the thoracic girdle or aimed close from behind for lizards.

Question 29

Considerations for anaesthesia recovery in exotics.

Answer 29

Monitor continuously until patient moving around and righting reflex back.
Temperature and environmental needs met (husbandry).
Pain score and manage pain.
– remember prey spp can hide pain well.
Encourage to eat e.g. syringe feeding, palatable.