Clinical: Farm Animal Anaesthesia Flashcards
Most of the anaesthetics & sedatives are
off-label in food-producing animals
Check local legislation!
Considerations for anaesthesia in ruminants?
Physiology/anatomy, local, food producing, handling/restraint
- physiology & anatomy: regurgitation, rumen tympany, salivation, size, pregnancy
- Importance of local: sedation & lcoal anaesthesia techniques –> IMPORTANT
- food producing: drug limitation, guess body weight
- handling/restraint: difficult to assess patient pre-anaesthesia
- weight accuracy: guess?
Regurgitation/aspiration occurs ruminants when…
- actively in light anaesthesia/intubation
- passively in deep anaesthesia
- rumen cannot be emptied of material: improtance of fasting, do NOT do in neonates
how do you prevent aspiration/regurgitation in ruminants?
- intubate ASAP after induction
- use cuffed tubes
- minimize head/neck mvmts
- consider gastric tube
How do you prevent ruminal tympany?
- appropriate fasting
- avoid highly fermentable food prior to GA to decrease ruminal gases
- stomach tube
- No N2O
How do you treat ruminal tympany?
trochar & cannula if too much tympany
What recovery position do ruminants need to be in for recovery of ruminal tympany?
- sternal for eructation
How much salivation is produced per day in a ruminant?
- 50-150L/day
What should you consider in regards to anaesthesia and ruminant salivation?
- can lead to obstruction of respiratory tract
- is a hazard in anaesthesia
What is the treatment of salivation during anaesthesia?
- infuse LRS & bicarb to minimise acid-base disturbances
- collect salive & readmin via stomch tube
Prevention of salivation issues in ruminants
- elevate poll above the muzzle
- anticholinergics are NOT RECOMMENDED –> makes secretions thicker
Ruminants have a tendency to hypoventilate in anaesthesia because…
they have a smaller tidal volume due to large rumen/viscera on diaphragm, tympany, or dorsal recumbency
How do you treat hypoventilation in ruminants? Prevention?
- Txt: IPPV prone to alveolar rupture if PIP > 25 cm H2O
- Prevention: fasting, monitor EtCO2 & ventilate
Hypotension is caused by…
tympany or IPPV
How do you prevent hypotension in farm animals?
- fasting
- monitor EtCO2 & ventilate as needed
- can give Noradrenaline as CRI
Neuropathy/myopathy is common due to…
positioning, lack of padding
Difficult intubation in goats and sheep is due to
small opening of the mouth making difficult visualisation of the larynx and they have smaller trachea than other animals
When intubating cattle, your hand acts as
the laryngoscope
Recovery should be done in … to avoid…
sternal
avoid ruminal tympany due to eructation
Premedications in farm animals
- Xylazine - use smaller doses (goats > sheep > cattle), caution in pregnant, pulm oedema risk in sheep/goat
- Detomidine
- Butorphanol
Induction agents in farm animals
Ketamine
Thiopental
Unlicensed: Propofol, Alfaxalone
Research animals have different reqmts
Inhalant anaesthesia in ruminants
Isoflurane
Reqs 28d withdrawal
Triple drip
GGE not licensed, cannot be used
Depth monitoring in ruminants
- Palpebral reflex lost at light planes
- ventral eye rotation (great cattle, less in goats/sheep)
- nystagmus unrelated to depth (except eq)
- involuntary swallow reflex w/o other signs of light anaesthesia –> may be getting light
Standard protocols in ruminants
- Premed: alpha-2 agonist & opioid
- Induction: ketamine & thiopental
- Maintenance: isoflurane (Cascade)
- Analgesia: Ketamine CRI, local/regional, NSAIDs
Because llamas & alpacas are not considered food animals in IE, this means…
there are fewer drug limits compared to other ruminants
Llamas & alpacas adult sizes
llamas: up to 200 kg
alpacas: 60 kg
llamas & alpacas are adapted to…
high altitude adaptions w/ low oxygen levels
Llamas & alpaca catheter placement
- jugular (has valves, next to vagosympathetic trunk & carotid a.)
- auricular v. is alternative, but only for maintenance fluids, not boluses
Preparing llama/alpaca for Sx
- starve for 24 hrs
- water deprivation 8-12 hrs
Complications w/ Sx for llamas/alpacas
- difficult intubation
- tympany
- regurgitaiton, aspiration
- obligatory nasal breathers
- extubate only when actively coughing/swallowing
Endotracheal intubation in llamas/alpacas
- direct visualisation of larynx tricky
- desensitise larynx before intubation
- elongated soft palate can obstruct view
- long laryngoscope blade req’d
- narrow opening of the mouth
- small ETT sizes req’d (8-10 mm)
- nasal intubation possible
- head perpendicular, stylet first, then guide ETT
- worse to intubate than goats/sheep
Extubation alpacas/llamas
- wait until can withdraw tongue
- monitor for nasal congestion/obstruction
- monitor for displaced soft palate (snoring)
Recovery in llamas/alpacas
- sternal position
- heads up, supported
- oxygen as needed
- late extubation
- will stand when they want
Pigs are all considered…
food producing
Pigs are difficult to…
restrain
IM injections in swine
- avoid gluteal & quadriceps muscles in meat production animals
- difficultt o place IV w/o sedation 1st
IV injections in swine
- Auricular first, then Cephalic if needed
- use heat lamp to find vein
Intubation in swine
- Lidocaine for laryngeal spasm
- small tube sizes compared to dogs of similar body weight
- head & neck fully extended
- caution w/ long ETT, can accidentally blcok the tracheal bronchus
- caution so you don’t perforate the larynx
Recovery in swine
- extubate when laryngeal reflexes are present
- warm environment/monitor temp
- keep in sternal
- alone - could be cannibalised/mutilated by others in pen so keep alone until fully awake & aware
- quiet environment
Potential complications of anaesthetic treatment in swine
- laryngospasm
- fluid accumulation in larynx
- difficult intubation
- hypothermia
- malignant hyperthermia (less common now)
- recovery –> respiratory obstruction, cannibalism
Malignant hyperthermia in swines
- genetic (recessive) hypermetabolic syndrome
- increased cell metabolism –> elevation of CO2 & lactic acid
- commonly affected: landrace, pietrain, duroc, poland-china
- Triggers: stress, succinylcholine, volatile agents, N2O, isoflurane
- clinical signs: hypercapnia, muscle rigidiy, increased temp, metabolic & resp acidosis, tachypnoea, tachycardia, hot/pink skin
- Txt: difficult, stop triggers, cool body, Dentrolene muscle relaxant
Premedication of swine
- Azaperone, not analgesic, deep IM inj, long recoveries
- Alpha-2 agonists: ketamine, butorphanol
- Suitable protocol: Detomidine, Ketamine, Butorphanol
Induction & maintenance in swine
Induction: ketamine, thiopental
Maintenance: Isoflurane
Analgesia in swine
NSAID: meloxicam, flunixin –> prone to GI ulceration
Opioids: morphine, fentanyl, pethidine, butorphanol (cascade)
Locals
