Anaesthesia of Rabbits, Rodents and Ferrets Flashcards
17.2.14
When do the majority of anaesthesia related deaths in rabbits occur?
Postoperatively
Which type of rodent has the highest risk of death? Why?
Guinea pig
Difference between MAC dose and respiratory arrest dose is very small.
Give an example of a predator and prey rodent species
Predator: Ferret
Prey: Rabbit
What are the most common reasons for anaesthesia in rabbits?
Dentals
Neutering
Traumatic injuries (inc. flystrike)
Diagnostic imaging
What animal should rabbits be thought of as..?
Tiny horses!
What are the most common anaesthetic problems in rabbits?
Post-operative ileus*
Difficultly intubating and ^risk of blockages
Obesity
*What are three things associated with post-op ileus? How can they be overcome?
Pain - provide good analgesia
Anorexia - aim for fast recovery
Stress - get rabbit home asap
What is the most common subclinical disease of rabbits?
Respiratory
- Pasteurellosis
(Rabbit snuffles)
§Assume all rabbits have respiratory dysfunction§
What is referred to as a “carpal handkerchief?”
Nasal discharge seen on medial aspects of the forelegs with rabbit snuffles
Why may dental problems in themselves cause an ^anaesthetic risk?
Has probably gone unnoticed for weeks -> malnourishment and dehydration on presentation
What five points should be checked during pre-aneastheitc examination of the rabbit?
- History ( esp. previous illness and previous anaesthesia)
- Check for visual signs of illness and dyspnoea
- Signs of respiratory disease
- normal clinical exam
- Check renal function if any signs of incontinence*
*What pathogen is associated with urinary incontinence in rabbits?
Encephalitozoon Cuniculi
Name 4 places blood samples may be taken from a rabbit.
Cephalic v.
Marginal ear v. §NOT CENTRAL OBVIOUS VESSEL IN EAR - THIS IS AN ARTERY!§
Lateral saphenous v.
Jugular v.
Why must care be taken when sampling from the ear of a rabbit?
Do NOT use large central vessel - this is the central ear ARTERY.
Should rabbits be starved pre-aneasthesia?
No - they don’t vomit. But do check mouth is clear.
How may dehydration be corrected in the rabbit?
Crystalloid fluid - up to 30-50ml sub cut
Up to 50mls intraperitoneally (Lower Right Quadrant)
IV (Rate depends on urgency)
When should an IV catheter be placed?
Pre-induction (potentially post-sedation)
What may be applied before catheterisation?
EMLA cream - apply~1hr pre venipuncture, occlude from air (cover in plaster/rubber gloves etc.)
What gauge catheter should be used for a rabbit? What colour is this?
22G (Blue) or
24G (Yellow)
What does EMLA stand for? What is it?
Eutectic Mixture of Local Anaesthetics
Lidocaine and Prilocaine
What drug is often used before catheterisation but does NOT actually work?
Intubeaze (designed for cats larynx intubation)
Does not work on skin!
Are pre-meds always given to rabbits?
No. Depends on technique and temperament.
What are the most common pre-meds for rabbits?
Hypnorm
Medetomidine (a2 ag)
Pre-emptive analgesia eg. butorphanol, buprenorphine, meloxicam
What other kind of induction (other than injectables) is possible? When is this used?
Mask induction
Should be AVOIDED at all costs
- causes breath holding and bradycardia -> hypoxeamia, hypercapnia and acidosis
- sevoflurane often advocated over isoflurane due to lack of smell, but this is not actually any better (mask placement causes diving reflex, not smell)
- may be possible if pre-med sedatives given.
What do all anaesthetic agents do to respiration?
Respiratory depression
What is hypnorm? How is it given? Licensed?
Induction agent - licensed
Fentanyl (Opiod) and Fluanisone (Azaparone) mixture (IM injectable)
What effects does hypnorm have?
Profound respiratory depression (opioid component) reversible using opioid ants.
Poor muscle relaxation (usually used in conjunction benzodiazepene eg. medazolam/diazepam)
Long recovery
Fentanyl induced ileum possible as in horses due to opioid.
How are ketamine combinations given? Licensed?
IM or SC - not licensed.
What ketamine combination gives best surgical conditions?
Ketamine/a2 ag/opioid
What drug may be used to reverse the effects of an a2 ag? Dose?
Atipamezole (a2 ant)
Dose = 5x medetomidine
What is the most profound negative effect of ketamine induction? How can this be rectified?
Hypoxeamiea
- give O2
What are the disadvantages of ketamine combination induction?
Variable effect Peripheral vasoconstriction - may hinder pulse ox - pale mucous membranes - difficult to find wins for blood samples
Give 2 examples of other injectable induction agents (IV)
Propofol
Alfaxolone
What must always be done before intubation?
Inspect mouth for food
Give oxygen
Why is intubation more difficult in rabbits?
Tongue, cheek teeth and epiglottis are large
Laryngeal opening is small
Sharp angle between mouth and larynx
Prone to laryngeospasm and laryngeal oedema
What are the two methods of intubation?
Blind technique (listen for air) Laryngeoscope/otoscope
What are the two other options for intubation? Should they be used?
Laryngeal mask airway (LMA)
Nasal intubation - do not use as pushes infection into lungs
What should be one before passing the tube through the larynx?
Spray with local anaesthetic
How can you confirm that the trachea has been intubated?
Check for condensation on the tube
How should the cuff of a laryngeal mask airway be inflated?
It shout NOT! Will prevent blood form flowing back though the tongue.
What is a V-Gel?
Similar to a LMA but does not pass through vocal folds - made of a soft silicon stuff. Becoming more common.
What should you do if it is impossible to intubate?
Make sure oropharynx is completely clear of secretions
Extend head and neck
Clean secretions regularly from airway (cotton bud/suction)
Use anti-sialogogue at or after induction*
What is an anti-sialogogue?
Which anti-sialogogue is best to use in rabbits? Why?
Glycopyrrolate better than atropine as rabbits have an enzyme that destroys atropine.
When should oxygen be used in anaesthesia? How is it best delivered?
ALWAYS. Via ETT as this enables IPPV if necessary.
When are volatile anaesthetic agents necessary?
When short acting induction agents are used eg. proposal, alfalaxone
How can long acting anaesthetic agents be used to maintain anaesthesia?
Top up with volatile agent or
Quarter of initial dose of drug
Which volatile agent is licensed in rabbits? What other alternative is there?
Isoflurane licensed
Sevoflurane also a potential
Both have similar potency to other species
What circuits are suitable for use during rabbit anaesthesia?
T piece
Mini-lack
Humphrey
- depending on size
Name two products used to lubricate the eyes
Lacrilube
Viscotears
How may intraoperative fluids be given?
SC/Intraperitoneal injection (10-15ml/kg) after induction
IV infusion (10ml/kg/hr)
Warm fluids!
What should be monitored re: fluids during anaesthesia?
Blood loss
What is the average blood volume of a rabbit?
60-80ml/kg
Where may a pulse be taken on the rabbit?
Central ear artery
How may circulatory changes be seen in some specific types of rabbit?
Albinos - cyanosis and pallor in eyes seen with a2-mediated vasoconstriction
How can anaesthetic depth be monitored in the rabbit?
Tail pinch (lost at light-med plane) Toe pinch (lost at med-deep plane) Ear pinch (lost at medium-deep plane) NOT palpebral - useless.
What is capnography?
Measuring CO2 levels
How may post-operative ileum be prevented?
Good analgesia
Avoid stress - keep way from other species
Own food/water containers
Syringe feeding? ("Oxbow Critical Care")
Prokinetics to increase gut movement**Give two examples of pro kinetics.
Ranitidine (2-5 mg/kg)
Metoclopramide (0.5-1 mg/kg)
What advice should be given to all owners of post-op rabbits?
If not eating and passing feaces within 24hours must be brought back to the surgery - ILEUS KILLS
What are the three most common causes of acute pain in rabbits?
Trauma and surgery
Ileus
Otitis externa
What are the three most common causes of chronic pain in rabbits?
Dental disease
Arthritis
Neoplasia (uterine adenocarcinoma in entire does)
What is the commonest sign of pain in rabbits?
Anorexia
What are other signs of pain in rabbits?
Teeth grinding (esp. visceral pain)
Immobility
Reduced respiration rate (deep breaths, nostrils flare)
Epiphora and serous nasal discharge
Which analgesics are licensed in rabbits?
NONE.
What are the commonest opioid used in rabbits?
Buprenorphine
Butorphanol
What side effects does morphine have?
Can cause ileus
What is the commonest NSAID used in rabbits? How does the dose differ cf. dogs and cats?
Meloxicam
- well tolerated long term
- higher dose than in cats and dogs (0.5-0.6mg/kg)
In what situation would rodents need to be starved pre-aneasthesia?
If >200g
- starve for 1-3 hours
When should water be removed from rodents pre-aneasthesia?
One hour pre-induction
In which species is the lateral tail vein used for IV access?
Rats
Mouse
Gerbils
Which vein is used for IV access in the guinae pig?
Medial metatarsal vein
How can excessive salivation be prevented? Which species is this particularly important in?
Atropine (0.06mg/kg SC)
Guinea pigs and chinchillas
Which rodent species has an abnormal soft palette? What does this mean?
Guinea pigs
- cannot be intubated
Why may normal pulse oximeters not work on rodents?
Pulse rate too high
Which analgesic agents are licensed in rodents?
NONE.
Which analgesics are commonly used in rodents? How often do they need to be dosed?
Opioids
- full agonist shorter duration of action
- Buprenorphine 6-12 hours (can be administered in sweet food)
- Butorphanol every 4 hours
NSAIDS
- no adverse reactions
- same precautions as dogs and cats
- avoid prolonged used
-single dose of meloxicam or carporfen lasts 12-24hours
-Meloxicam tastes of honey and is liquid
What animal is a ferret similar to physiologically?
Cat
Why do ferrets provide a catheterisation challenge?
Thick skin
What other challenges do ferrets provide?
Underlying disease
Hypoglyceamia - do not fast for more than 4-6 hours
Small peripheral veins
Hypotension
What tumours are ferrets prone to developing?
Insulinomas
