Anaesthesia - animal specifics Flashcards
2 groups of drugs used to sedate horses?
phenothiazines (ACP)
alpha 2 agonists (detomidine)
How is acepromazine as a horse sedative?
- limited sedation
- better if combined with an opioid
- can cause hypotension
- be careful as can cause priapism in stallions
- very safe - halves risk of death
what is a common alpha 2 agonist combination used to sedate horses?
detomidine and morphine
- deep does related sedation
- can cause bradycardia , reduced CO, bp changes, high blood glucose, high urine output, gut stasis
Pre-op considerations for horses?
- 8-12 hr starvation
- remove shoes
- wash out mouth
What is the normal pre-op drug regime for horses?
ACP in box
alpha 2 agonist and opioid in induction suite
Why is TIVA not really used in the horse?
very expensive
What are the 3 techniques for horse induction?
- ketamine based
- hypnotic
- guiaphenesin
How does IV ketamine induction in the horse work / what do you do?
- Give a 2 agonist first so it calms down
- give ketamine +/- benzodiazepine
- takes 1-3 mins to go down
- lasts for 15-30 mins
- fast recovery
what is the hypnotic technique for horse induction?
- propofol / alfazalone / thiopental
- give large volumes rapidly
- expensive
What is guiaphenesin technique for horses?
- its a muscle relaxant so can give then induce with ketamine or thiopental
- very long acting
What volatile agent is licensed in the horse?
Isoflurane
What volatile agent is used via the cascade in the horse and why?
Desflurane + sevoflurane
-fast induction, stable anaesthesia and rapid recovery
What are complications of isoflurane in the horse?
respiratory depressant - IPPV
hypotension
Why is nitrous oxide controversial in the horse?
can cause hypoxia
diffuses into gut spaces so increases pressure on lungs
what is the most economical circuit for the horse?
circle
can use rebreathing
How is arterial bp measured in the horse?
direct via canula in the facial artery
What are the 2 positions horses can be in during anaesthesia?
lateral recumbency
dorsal recumbency
what are the considerations when a horse is in lateral recumbency?
- pull under front leg forward
- upper limb parallel to table
- very soft padding
What are the considerations when a horse is in dorsal recumbency?
dont lock stifle
raise head but dont over-extend as can stretch laryngeal nerve
What intra-op analgesia is used in the horse?
- most commonly = ketamine
- alpha 2 agonists
- lidocaine (need to stop 20 min before end of surgery for better recovery)
6 common complications in horse anaesthesia?
hypotension hypercarbia hypoxaemia cardiac arrhythmias cardiac arrest muscle and nerve damage
What to do if a horse is hypotensive?
- reduce volatile agent
- fluids
- ionotropes
- slightly overventilate (high CO2 is circulatory stimulant)
- DONT use vasoconstrictors
What to do if a horse is hypercarbia?
-IPPV but will decrease HR by increasing intrathoracic pressure
What to do if a horse is hypoxaemic?
- speed up surgery
- horse can tolerate it well
- due to V/Q mismatch as lungs being squashed
What to do if a horse has an arrhythmia?
- give anticholingergic (very sensitive to vagal stim)
- if tachycardic remove cause (toxin, hypovol, adrenaline)
What to do if a horse has a cardiac arrest?
- can still breath
- external cardiac massage by jumping on knees
- IPPV
- adrenaline
What to do if a horse has muscle and nerve damage post op?
can be form reduced perfusion
try to support
What are considerations with the horse during recovery?
- POSITION - if been dorsal - lateral, leave on same side to reduce hypoxia but turn over to reduce muscle damage
- remove ETT as soon as in recovery box
- dont want too fast or too slow recovery
- analgesia before pain commences
Most common drug protocol used for horse anaesthesia
- ACP in box
- a 2 agonist and opioid (detomidine and morphine) in induction suite
- Ketamine and benzodiazepine to induce
- isoflurane to maintain
- ketamine as intra-op analgesia
What procedure do you do standing and under GA in farm animals?
Standing - flank laparotomy, de-claw, de-horn, teat surgery, castration
GA - umbilical hernia repair, urethostomy, orthopaedic, enucleation
How is regurgitation prevented in cattle?
starving for 18-24 hr, remove water for 12 hr
- good depth when intubating
- good fitting tube
- keep mouth low so can drain
What is the consideration with lots of saliva production?
fluid and electrolyte loss
What is a consideration with ruminants and their rumen?
cant eructate when anaesthetised and still fermenting so can get bloat / ruminal tympany
pass NGT if needed
Why can cows get hypoxaemia?
rumen squashing lungs so get V/Q mismatch
IPPV
What is used for farm animal sedation?
A 2 aonist
pulmonary oedema, reduced eructation, reduced swallowing, increased urine, uterine contraction
What is used for farm animal induction?
Ketamine (laryngeal reflex remains)
thiopentone (long recovery but fast acting)
What inhalational agent can be used for cattle?
isoflurane
What are some anaesthetic considerations for camelids?
- prone to bloat
- obligate nasal breathers
- 3 stomachs
- lingual torus
- jugular catheter either high or low as vertebral wings extend far round
- classed as pets
- recover in sternal recumbency
- remove ETT with cuff inflated when can stay sitting
- keep as herd
What are some anaesthetic considerations for pigs?
- starve for 6 hrs
- IM first as hard to catch for IV (use fluid extension set)
- hard to intubate
What drug protocol is used in pigs?
Sedate - azaperone (penile prolapse)
Induce - ketamine / thiopentone
maintain - isoflurane
What is malignant hyperthermia in pigs?
- faulty gene so Ca channel stays open in sarcoplasmic reticulum in muscles so get muscle rigidity
- stimulated by inhalational agents and caffeine
- active cooling, fluid, remove trigger, IPPV, bicarb to increase pH, monitor K
- can test for gene
what is the anaesthetic risk for horses and rabbits?
Horses - 1/100
Rabbits - 1/72
What do you assume with rabbits?
all have some degree of respiratory dysfunction
How do you prepare rabbits for anaesthesia?
- blood from cephalic / marginal ear vein
- accurate weight
- no need to starve
- check mouth before intubating
- EMLA cream before catheter
- correct dehydration
- give analgesia
- avoid mask induction as they breath hold
How are rabbits induced?
- hypnorm (fentanyl and fluanisone) - very resp depressant
- ketamine +a2 + opioid off license - peripheral vasoconstriction and pale mm
- propofol
- alflaxalone
What is a rabbit intubated?
- check mouth for food first
- give o2 before intubating
- blind or with laryngoscope
- can use a laryngeal mask
- hard as toungue / cheek teeth / epiglottis large and laryngeal opening is small
- sharp angle between mouth and larynx
- prone to laryngospasm
How are rabbits maintianed?
- oxygen
- volatile agent or inj
- 10-15 ml / Kg subQ fluid
- depth assessment by tail < toe < ear pinch (want just lost toe)
What circuits can you use for a rabbit?
t-piece
mini lack
humphrey
Rabbit recovery considerations?
- incubator?
- analgesia
- encourage to eat and go home ASAP
- need to eat and pass pellets in 24 hr
signs of pain in a rabbit
anorexia teeth grinding immobility reduced RR unkempt look
Rodent anaesthesia
- starve for 1-3 hrs if over 200g
- remove water 1 hr before
- examine mouth for food
- no licensed analgesia but use opioids / NSAIDs
- rat + mouse + gerbil - lateral tail vein
- guinea pig - medial metatarsal vein
Ferret anaesthesia
- treat like a cat
- thick skin so catheterisation hard
- insulinomas common so dont fast over 4-6 hrs
- sensitive to volatile agents
