Anaesthesia of Rabbits, Rodents and Ferrets Flashcards
Anaesthetic Risk: Rabbits - Risk of death
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
Anaesthetic Risk: Rodents
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)
rabbit - Common reasons for anaesthesia
Dental procedures
Neutering
Diagnostic imaging
traumatic injury
rabbit - Common anaesthetic problems
Post-operative ileus - Pain, Anorexia, Stress
Assessment of pain is more difficult
More difficult to intubate and small tubes can get blocked easily
Obesity
respiratory problems - rabbit
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
dental problems
may go unnoticed for weeks, so animals often dehydrated and malnourished on presentation
blood sampling
Cephalic vein
Marginal ear vein
Lateral saphenous vein
Jugular vein
preparation for anaesthesia
Accurate weight essential
No need to starve – they don’t vomit (but always check mouth at time of induction)
Correct dehydration
venous catheterisation
place IV catheter before induction of anaesthesia Apply EMLA cream to ear - 1 hour before venepuncture, and occlude it
May need sedating first
Topical Local Anaesthesia: Skin
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
premedication
May or may not be given - anaesthetic
technique + temperament of rabbit
In practice, either Hypnorm® or medetomidine
analgesia
induction with mask
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
hypnorm
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
ketamine combinations
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
injectable induction - disadvantages
Variable effect
Causes peripheral vasoconstriction – may hinder pulse oximetry
Can be difficult to take blood samples or find veins
Pale mauve mucous membranes
intubation
Always inspect mouth for any food material before
Always give oxygen before
intubation difficulties in rabbits
Tongue, cheek teeth and epiglottis are large
laryngeal opening is small
sharp angle between mouth and larynx
Prone to laryngospasm and laryngeal oedema
if impossible to intubate
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
maintenance of anaesthesia
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
intraoperative fluids
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
recovery
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
Preventing post-operative ileus
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
Signs of pain in rabbits
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
Pre-anaesthetic preparation - rodents
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
IV access - rodents
Rats, mouse and gerbil – lateral tail veins
Guinea pigs - the medial metatarsal vein can be used
Opioids - rodents
Full agonists may have shorter duration of action
Buprenorphine 6-12 hours - Can be administered in sweet food
Butorphanol every 4 hours
NSAIDs - rodents
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
ferret anaesthesia
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
ferret challenges
Underlying disease Hypoglycaemia: don’t fast for more than 4-6 hours (insulinomas relatively common) Hypothermia Small peripheral veins Hypotension
