Anaesthesia of Rabbits, Rodents and Ferrets

Question 1

Anaesthetic Risk: Rabbits - Risk of death

Answer 1

Healthy rabbits 0.73% (1 in 137) 
Sick rabbits 7.37% (1 in 14) 
Overall 1.39% (1 in 72) 
6% on induction 
30% during maintenance 
64% postoperatively: most in first 3 hours 
40% cardiopulmonary arrest 
60% unknown

Question 2

Anaesthetic Risk: Rodents

Answer 2

Guinea pig 3.8% (1 in 26)
Hamster 3.66% (1 in 27)
rat 2.01% (1 in 50)
Other small mammals 1.72% (1 in 58)

Question 3

rabbit - Common reasons for anaesthesia

Answer 3

Dental procedures
Neutering
Diagnostic imaging
traumatic injury

Question 4

rabbit - Common anaesthetic problems

Answer 4

Post-operative ileus - Pain, Anorexia, Stress
Assessment of pain is more difficult
More difficult to intubate and small tubes can get blocked easily
Obesity

Question 5

respiratory problems - rabbit

Answer 5

Subclinical respiratory disease v common
assume all rabbits have some degree of respiratory dysfunction
Nasal discharge a useful sign of respiratory disease
Discharge may also be on medial aspects of forelegs

Question 6

dental problems

Answer 6

may go unnoticed for weeks, so animals often dehydrated and malnourished on presentation

Question 7

blood sampling

Answer 7

Cephalic vein
Marginal ear vein
Lateral saphenous vein
Jugular vein

Question 8

preparation for anaesthesia

Answer 8

Accurate weight essential
No need to starve – they don’t vomit (but always check mouth at time of induction)
Correct dehydration

Question 9

venous catheterisation

Answer 9

place IV catheter before induction of anaesthesia Apply EMLA cream to ear - 1 hour before venepuncture, and occlude it
May need sedating first

Question 10

Topical Local Anaesthesia: Skin

Answer 10

EMLA cream: Eutectic Mixture of Local Anaesthetics 
Lidocaine and Prilocaine 
Absorbed across intact skin 
Apply 30 minutes before (occluded) 
Intubeaze doesn’t work on skin

Question 11

premedication

Answer 11

May or may not be given - anaesthetic
technique + temperament of rabbit
In practice, either Hypnorm® or medetomidine
analgesia

Question 12

induction with mask

Answer 12

AVOID IF POSSIBLE!
Causes breath holding and bradycardia (diving reflex) hypoxaemia, hypercapnia + acidosis
No advantage of sevoflurane over isoflurane
May be safer if premedicated first

Question 13

hypnorm

Answer 13

injectable
mixture of fentanyl and fluanisone  
Profound respiratory depression 
Poor muscle relaxation 
Respiratory depression reversible at end of surgery 
Long recoveries 
Fentanyl-induced ileus is possible

Question 14

ketamine combinations

Answer 14

injectable
unlicensed
Ketamine/α2 agonist/opioid gives best surgical conditions
α2 can be reversed with atipamezole (5 × medetomidine dose)
spectacular hypoxaemia if you don’t give oxygen

Question 15

injectable induction - disadvantages

Answer 15

Variable effect
Causes peripheral vasoconstriction – may hinder pulse oximetry
Can be difficult to take blood samples or find veins
Pale mauve mucous membranes

Question 16

intubation

Answer 16

Always inspect mouth for any food material before

Always give oxygen before

Question 17

intubation difficulties in rabbits

Answer 17

Tongue, cheek teeth and epiglottis are large
laryngeal opening is small
sharp angle between mouth and larynx
Prone to laryngospasm and laryngeal oedema

Question 18

if impossible to intubate

Answer 18

Make sure oropharynx is clear of all secretions + food material
Extend the head and neck
Clean secretions regularly from airway (cotton bud or suction)
Use an anti-sialogogue at or after induction

Question 19

maintenance of anaesthesia

Answer 19

always give oxygen
Volatile agents necessary if short acting induction agents are used (propofol, alfaxalone)
With longer acting drugs, can top-up with either volatile agent or with ¼ of their initial dose Isoflurane or sevoflurane both suitable
Ensure eyes are well protected

Question 20

intraoperative fluids

Answer 20

Either by subcutaneous or intraperitoneal injection (10 - 15 mls/kg) after induction
intravenous infusion at 10 mls/kg/hr
make sure fluids are warmed to body temperature
monitor blood loss

Question 21

recovery

Answer 21

Continue measures to prevent heat loss – incubators very useful
Provide appropriate analgesia
Encourage eating as soon as possible
If not eating and passing normal faecal pellets within 24 hours after going home – they MUST be brought back to the practice for treatment

Question 22

Preventing post-operative ileus

Answer 22

Good analgesia
Avoid stress - hospitalize away from other species if possible
get owners to bring in own food and water container
consider syringe feeding
Prokinetics

Question 23

Signs of pain in rabbits

Answer 23

anorexia (commonest sign)
Grinding of teeth (especially visceral pain)
Immobility
decr respiratory rate
Acute pain - epiphora and serous nasal discharge
Chronic pain – often look unkempt

Question 24

Pre-anaesthetic preparation - rodents

Answer 24

No need to starve for long periods
Remove water one hour before induction of anaesthesia
Always examine mouth before induction and wash out any food material if necessary
In guinea pigs and chinchillas, atropine given at 0.06mg/kg SC can be very useful to prevent excessive salivation

Question 25

IV access - rodents

Answer 25

Rats, mouse and gerbil – lateral tail veins

Guinea pigs - the medial metatarsal vein can be used

Question 26

Opioids - rodents

Answer 26

Full agonists may have shorter duration of action
Buprenorphine 6-12 hours - Can be administered in sweet food
Butorphanol every 4 hours

Question 27

NSAIDs - rodents

Answer 27

No reports of adverse reactions
Treat with same precautions as in dogs and cats
Avoid prolonged use
Single dose of meloxicam or carprofen lasts 12-24 hours
Meloxicam tastes of honey and comes as a liquid

Question 28

ferret anaesthesia

Answer 28

Treat it like a cat
All the cat anesthesia applied to the ferret
Thick skin - catheterization challenge
Various injectable combinations
Injectable premedication follow by inhalant anesthesia (isoflurane/sevoflurane)
Alpha-2 agonist with ketamine combination

Question 29

ferret challenges

Answer 29

Underlying disease 
Hypoglycaemia: don’t fast for more than 4-6 hours (insulinomas relatively common) 
Hypothermia 
Small peripheral veins 
Hypotension