Flashcards in Farm animal and camelid anaesthesia Deck (58)
What are some examples of surgeries do you need a GA for?
- umbilical hernia repair
- orthopaedic (not all)
- enucleation (depends on species)
Give some examples of surgeries you can use a sedation and local anaesthetic technique
- flank laparotomy
- RDA or LDA
- teat surgery
List pre-anaesthetic considerations for ruminants - 8
- handling, restrain, accurate weight
- bloat (tympany)/rumen atony
- hypoventilation and hypoxaemia
- fluid and electrolyte problems
Outline regurgitation as a consequence of anaesthesia in ruminants
Can lead to aspiration pneumonia which can be fatal
- ACTIVE - light plane of anaesthesia (commonly at intubation)
- PASSIVE - deep anaesthesia (cardia relaxation)
How can you reduce the risk of regurgitation in ruminants? 6
- Reduce rumen fill (starve 18-24 hours, not if < 3 months old)
- good depth of anaesthesia when intubating
- good fitting ETT and properly blown up cuff
- position of head (fluid to drain into mouth)
- stomach tube
How does ketamine affect salivation?
- Ketamine (licensed induction agent) stimulates further production. Can lead to problems at intubation and electrolyte imbalances.
- Tx = atropine (L but never in UK food chain)
Why do you get bloat (tympany)/ rumen atony with with anaesthesia?
no eructation when anaesthetised --> reduces FRC and venous return --> continued fermentation can lead to pH shift and atony
How can you prevent bloat (tympany)/ rumen atony with anaesthesia? 2
- adequate starvation and water withholding time
- placement of a rumen tube or trochar to evacuate gas
Describe hypotension in ruminants under GA
- much less likely compared to horses
- deep planes of anaesthesia
- high xylazine doses or use of ACP (NL) implicated
- support required
What might cause hypertension in adult bulls and cattle under GA? (2 theories)
- High CO2 (due to hyperventilation, causes increased CO, when ventilated to reduce CO2, the ABP remains high)
- changeover from PS to S dominance as a result of anaesthesia
Why are ruminants more prone to airway damage during IPPV?
less fibrous connective dtissue
Why does hypoventilation and hypoxaemia occur in GA ruminants? 3
- drug induced respiratory depression
- chemoreceptor depression
- large rumen (and any bloat) --> small TV and only slightly increased RR, reduction in FRC (causes airway closure and VQ mismatch), decreased venous return (reduced CO).
Outline the likelihood of myopathy and neuropathy in ruminants under GA versus horses?
Ruminants are less prone to myopathy but neuropathy is more common.
AVOID BY: positioning, padding, ABP, oxygenation and perfusion
What sedative is used in ruminants?
ALPHA 2 AGONISTS --> sedation, anxiolysis, recumbency, analgesia, mm relaxation. Ruminants are very sensitive to these (esp. sheep and goats). Xylazine and detomidine (L-cow)
What are the side effects of alpha 2 agonists in ruminants? 7
* Pulmonary oedema - sheep and goat (xylazine)*
- reduced eructation (tympany)
- reduces swallowing (saliva in oropharynx)
- copious urine production
- osmotic diuresis
- urethral outflow issues
- oxytoxin like effect --> uterine contractions
What can be used for induction in ruminants? 2
Ketamine or thiopentone
Properties - induction with ketamine in ruminants - 4
- dissociative anaesthetis (use IV or IM)
- excellent analgesic
- mm rigidity
- laryngeal reflexes remain
Properties - induction with thipentane in ruminants - 5
- very fast acting
- no veterinary licence available
- very irritant so must go IV (extravasation --> necrosis)
- accumulation can lead to prolonged recoveries
- not in thin/debilitated animals
Are there any injectable agents for induction in ruminants?
No (but they include propofol, benzodiazepines, GCE, alphaxalone, chloral hydrate)
What is propofol good for?
Injectable induction of small ruminants as smooth induction and recovery. NOT LICENSED.
What are benzodiazepines good for?
Injectable induction. small ruminants, sedate neonates and debilitated animals well. NOT LICENSED
What is GCE good for?
Injectable induction. good centrally acting mm relaxant. NOT LICENSED
What is alfaxalone good for?
Injectable induction. used for goat disbudding. NOT LICENSED
What is chloral hydrate good for?
Injectable induction. old drug for sedation/anaesthesia. sedation acceptable, poor for GA. NOT LICENSED.
What are the 2 main ways or providing analgesia in ruminants?
*** NSAIDs (licensed - meloxicam, flunixin, ketoprofen, carprofen, tolfenamic acid)***
- OPIODIS (NL in UK, include butorphanol, buprenorphine, morphine/methadone, pethidine)
Name 4 inhalation agents used in ruminants
* Isoflurane (licensed)
- Sevoflurane (NL)
- Desflurane (NL)
- Halothane (NL) - hepatotoxicity
How can you anaesthetise smaller ruminants?
you ca mask them down
What are your venous access options in ruminants?
- JUGULAR - deeper than horse
- TAIL VEIN - often artery is used
- CEPHALIC - small ruminants
- MILK VEIN - don't use unless nothing left
What do you need to consider when intubating ruminants?
Laryngoscope as blind is difficult (long blade). Method is by internal palpation in adult cattle. In young cattle and small ruminants use a laryngoscope as in small animals - need a stylette to stiffen the ETT.