Rabbit, rodent and ferret anaesthesia Flashcards
How does small size affect anaesthesia
- venous access
- intubation
- thermoregulation
- anaesthetic monitoring
- haemorrhage significance
- easily stressed (prey)
- often have SC disease
- difficult to assess pain (prey)
- rapid metabolism
- post-anaesthetic ileus common
- short lifespan
What are pre-GA considerations for small mammals?
- full CE for underlying problems
- obtain accurate weight
- bloods (geriatric or sick, never in rodents)
How much blood can be taken form a small mammal?
only 0.5%-1% bodyweight
Outline steps of stabilisation - 2
- appropriate hospitalisation
- fluids
- nutrition
- analgesia
- tx underlying disease
- gut stimulants
What is the maintenance fluid requirement for small mammals?
100ml/kg/day (i.e. twice that of dogs and cats!)
How can fluids be administered to small mammals?
SC, oral, IV or intra-peritoneal (IP) - vary routes with large volumes
What should you add to SC fluids?
Hyaluronidase 1500IU/L to help absorption
How do you place an IV catheter?
Clip and apply topical EMLA cream 45-60 minutes prior to catheter placement. Good restraint. Place after sedation only in VERY jumpy rabbits.
What should you be careful of when using the marginal ear vein?
artery in similar location
When do you fast small mammals?
Not necessary in rabbits or rodents.
Necessary in ferrets (4-6 hours) to prevent regurgitation and aspiration.
What 3 types of analgesic can be given?
NSAIDs
Opioids
Tramadol
How can pain be assessed in rabbits?
Difficult, currently much research is going into developing a pain score which includes signs such as:
- cheeks tucked up
- ears tightly back
- eyes half-closed
- tense
What other drugs might be given prior to induction?
Underlying problem tx
Prevent of likely complications (gut stimulant - ranitidine)
Why shouldn’t gas anaesthesia be used? 5
- Apnoea (may be fatal)
- Stress
- Dose-dependent cardio-pulmonary depression
- Irritates MM (increased ocular discharge and salivation)
- No analgesia
What are the benefits of gaseous induction? 4
- rapid
- rapid adjustment to depth
- rapid recovery
- useful if hepatic or renal compromise.
How can gaseous induction be improved?
- Consider pre-meds (opioid and midazolam combinations or Hypnorm at low doses)
- Sevoflurane less irritant than isoflurane
- quiet, dimly lit environment
What drugs are in Hypnorm? 2
Fentanyl and fluanisone
What do you need to know about Hypnorm?
Currently unavailable. Only licensed sedative for rabbits/rodents. Provides deep sedation but respiratory depression –> long recoveries.
How can you achieve gas induction (i.e. equipment)?
chamber or mask
What do you use in IM or SC induction?
TRIPLE combination - alpha2 agonist and ketamine +/- opioid
Benefits - IM or SC induction - 3
deep sedation
good analgesia
easily reversed –> rapid recovery
Disadvantages - IM or SC induction - 2
respiratory depression
bradycardia
What should always happen with IV induction?
Always pre-med first
What can you use for IV induction?
Propofol OR alfaxalone
Benefits - IV induction - 2
Rapid induction and rapid recovery
Disadvantages - IV induction - 3
IV access required
Significant resp. depression if quick infusion
Additional analgesia will be necessary.
Is intubation recommended for EVERY rabbit and ferret anaesthetic?
YES
What are the coniditions for intubation?
adequate sedation
pre-oxygenate first
don’t attempt >3 times (laryngeal damage)
Name 5 intubation techniques
- blind
- visual (otoscope)
- visual (laryngoscope)
- endoscopic
- laryngeal mask
Outline the steps in blind intubation
- preoxygenate
- check mouth - food/debris
- position rabbit with nose to ceiling
- introduce tube and listen for breathing sounds
- advance tube towards sounds.
Steps - visual intubation
- preoxygenate
- position nose to ceiling
- use otoscope to displace soft palate and visualise the larynx
- thread urinary catheter though cone
Outline laryngeal masks (v-gels)
increasingly common. Can be easier to place than ETTs but harder to confirm correct position. Always use with capnographs. Easily displaced.
Why is intubation not routinely performed in rodents?
- narrow gape
- palatal ostium
What is a palatal ostium?
rodent anatomical feature, it is the fusion of the soft palate to the base of the tongue which limits visibility with an otoscope/laryngoscope.
What are the 4 most important parts of maintenance?
ventilation, circulation, warmth and ocular lubricant
How can the patient be best vetilated?
position head and neck extended, thorax slightly elevated and ensure ETT is well-placed (harder for laryngeal masks)
Why should you be prepared to do IPPV?
apnoea is not uncommon during rabbit anaesthesia. mechanial or manual.
How many breaths per minute should you give on IPPV?
20-50bpm based on capnography
How should fluids be administered during GA?
Divide into IV boluses q15 minutes OR small syringe driver but beware of fluids losing heat. Consider using intra-osseous (IO) route in small patients.
How can you provide warmth?
- room temperature *
water-recirculatingheat mat, blankets, foil, bubble wrap, hot hands, microwaveable pads, warm fluids, minimise clipping BUT beware of burns
What should you monitor?
RESPIRATORY - RR, pattern, depth CARDIOVASCULAR - HR, pulse quality MM colour and CRT Temperature Reflexes - tail/toe pinch and jaw tone
Why do you use capnography?
to look at ventilation efficiency: RR, ETCO2, amount of CO2 being rebreathed.
When is capnography particularly useful?
for intubation to check correct positioning
What should you aim to maintain systolic BP at?
> 90mmHg (useful guide for fluid therapy)
Outline intra-anaesthetic problems that may arise.
- Occur quickly*
- Apnoea - commonest
- Cardiac arrest - follows apnoea quickly
- hypothermia - long procedures.
How should you be ready for an emergency?
same drugs/principles as cats/dogs
know doses and drugs
ideally always have IV access, consider IO if not.
Outline small mammal anaesthesia recovery - 5
- reverse induction agents (if necessary)
- extra heat
- don’t stop monitoring
- recoveries may be long
- most problems occur during this time
How can you minimise post-anaesthetic ileus?
- low stress environment
- gut stimulants
- nutrition
- analgesia
- keep in overnight if possible to ensure eating and faeces.
