Anaesthesia of birds and reptiles

Question 1

Anatomical and physiological considerations for bird anaesthesia

Answer 1

Low functional residual capacity, so any period of apnoea is a cause for concern

Neither dorsal nor ventral recumbency are good for long periods - unnatural

Air sacs (no actual exchange) and solid state lung

Two breaths for air to go in, through, and out again

Will go down much quicker than other animals, and come out quicker as well

Question 2

Fasting for bird anaesthesia

Answer 2

Just until the crop is empty, but with care (metabolism)

Small passerines: 30-40 minutes

Large parrots: 2-3 hours

Birds of prey: usually overnight - dependent on usual feeding/casting time

Question 3

Premed for bird anaesthesia

Answer 3

Ketamine: minor procedures, not used often

Intra-nasal midezalam: good for minor procedures, stressful administration though

Propofol: good for larger birds, needs iv access

Question 4

Induction of bird anaesthesia

Answer 4

• Mask with gentle restrain
  ○ Isoflurane
  ○ Intubate
  ○ Ayre’s T-piece or bain
  
  • Premedication makes a big difference
  • High dose to get it down then lower once down

Question 5

Intubation of birds

Answer 5

Remember complete tracheal rings and syrinx
○ Uncuffed
○ May need tapered tube
○ Dont go overlong and hit syrinx
If operating on the head can use air sac cannulation instead,
○ Just in front of leg
○ Caudal to rib cage

Question 6

Maintenance of anaesthesia in birds

Answer 6

IPPV
○ Need to give 1 to 2 breaths every minute
§ Due to stagnation in the air sacs, need to push the gas through them to force it to move
§ This is even if the bird is breathing for itself

Heart rate
○ Doppler
○ Oesophageal stethoscope
○ Good if everyone can hear the heart beat, early flag that something is about to happen

Heart rate: 250 bpm +
○ If you can count it, its probably too slow

Heart rate and doppler are essential to gauge depth

Pulse oximetry, but can be well oxygenated and still hypercapnic

Capnograph

Body temperature (hypo or hyper)
○ Geese or ducks are likely to get hyperthermic

Lubrication of eyes

Question 7

IV catheters in birds

Answer 7

wing vein

large birds can use metatarsal vein

small birds use carpal vein

Question 8

Signs of pain in birds

Answer 8

• Change in temperament
  
  • Reluctance to perch or feed as normal
  • Ruffled feathers - especially on nape of neck
  • Biting or chewing at area of discomfort

Question 9

Analgesia in birds

Answer 9

opioids (butorphanol and methadone)

NSAIDs (carprofen, meloxicam)

Gabapentin and tramadol

local analgesia (lidocaine)

Question 10

Starving reptiles for anaesthesia

Answer 10

• Herbivores: do not starve
  
  • Insectivores: 18-24hrs
  • Carnivores: 2-7 days or so
  • Remember they can all vomit

Question 11

Premed for reptiles

Answer 11

• Atropine/glycopyrrolate
  ○ Unlikely will need to treat ‘bradycardia’
  ○ Atropine can cause ileus in herbivores
  
  • Opiates
    ○ Butorphanol, but does it have much effect?
  • Local anaesthesia
    ○ Lidocaine
  • Medetomidine (can be reversed)
    
    • Medazolam

Question 12

Induction agents for reptiles

Answer 12

Isoflurane: if intubated

ketamine: variable, may be good for sedation

propofol: excreted in 30-40 mins

alfaxalone: ideal for patients with no iv access (geckos)

Question 13

IPPV for reptiles

Answer 13

required in periods of apnoea and in chelonia

2-4 breaths per min

Question 14

Signs of pain in reptiles

Answer 14

• Would it hurt any other vertebrate?
  
  • Some snakes become aggressive with pain
  • Chelonia may be depressed
  • BUT any reptile may become hyperactive as if trying to escape the pain

Question 15

Analgesia in reptiles

Answer 15

• Butorphanol (IM)
  
  • Methadone (IM)
  • Carprofen (IM, SC, or oral)
  • Meloxicam (oral or SC)
  • Tramadol (oral)

Question 16

Euthanasia in reptiles