Farm Animal Anaesthesia Flashcards
Give some examples of procedures performed under GA in farm animals..
Umbilical hernia repair Urethrostomy Orthopaedic Enucleation Median laparotomy Dehorning
Give examples of common procedures performed under standing sedation in farm animals…
Flank laparotomy C-section RDA, LDA Rumenotomy Declaw Dehorn Teat surgery Castration
What are the main preanaesthetic considerations in ruminants?
Manual handling and restraint Accurate weight Regurgitation Salivation Fluid and electrolye problmes Bloat Hypotension Hypoventilation Myopathy
What can cause regurgitation in farm animal anaesthesia?
Light plane of anaesthesia at intubation
Cardia relaxation during deep anaesthesia
Why is regurgitation a problem/
Aspiration pneumonia can be fatal
How can you minimise the risks of aspiration pneumonia due to regurgitation during anaesthesia of farm animals?
- Reduce rumen fill (starve 18-24 hours)
- Reduce rumen water (remove for 12 hours)
- Good depth of anaesthesia when intubating
- Well fitted ET tube
- Immediae cuff infation
- Position of head
- Stomach tube
Preanaesthetic considerations in terms of salivation for ruminants
Large volume produced
Aspiration at intubation
Buffer for rumen function - may have electrolyte imbalance (HCO3-)
Treat with atropine to make mucous thicker? Controversial
Preanaesthetic considerations in terms of bloat for ruminants
Fermentation produces large gas volime
No eructation when anaesthetised
Position important
Reduces functional residual capacity (FRC)
Reduces venous return
Continued fermentation can lead to pH shift and atony
Prevent:
Adequate starvation and water witholding time
Placement of rumen tube/trochar to evacuate gas
Preanaesthetic considerations in terms of hypotension for ruminants
Less likely than horses
Deep planes of anaesthesia
Support required (IV fluids)
Inotropic drugs limited in food producing animals
Preanaesthetic considerations in terms of hypertension for ruminants
Adult cattle
High CO2
Hypoventilation
Superficial inefficient breaths under anaesthetic
Changeover from parasympathetic to sympathetic dominance as a result of anaesthesia
Preanaesthetic considerations in terms of hypoventilation and hypoxaemia in ruminants
Increased CO2 levels and decreased O2 levels (IPPV often required)
Less fibrous tissue connective tissue = airway damage during IPPV if pressure high
Drug induced respiratory depression
Chemoreceptor depression
Large rumen Small tidal volume Increased rate Reduction in FRC V/Q mismatch Decreased venous return Decreased CO
Preanaesthetic considerations in terms of myopathy/neuropathy in ruminants
Less prone to myopathy than horses
Neuropathy more common (facial nerve paralysis)
Prevent:
Positioning, passing, oxygenation, perfusion
Slow recovery = give Mg to aid recovery as may have hypomagnesaemia
What sedatives can be used in farm animals? What are the effects associated?
Alpha 2 agonists
Xylazine
Detomidine
Sedation, anxiolysis, recumbency, analgesia, muscle relaxation
What are the side effects of using alpha 2 agonists as sedatives in ruminants?
Pulmonary oedema (sheep and goats) xylazine bronchoconstriction
Reduces eructation
Reduces swallowing (saliva in oropharynx)
Copious urine production
Oxytocin like effect = uterine contraction
What drugs are used for induction in ruminants?
Ketamine IV or IM
Excellent analgesic
Muscle rigidity
Laryngeal reflex remains
Thiopentone IV Fast acting Unlicensed Irritant if extravascular Prolonged recovery Not in thin animals as accumulates in fatty tissue so ↑ overdose
What drugs can be used for analgesia in ruminants?
Licensed NSAIDs (cattle only) Meloxicam Flunixin Ketoprofen Carprofen Tolfenamic Acid Metamizol
Opioids (none licensed in UK)
Butorphanol under cascade
Local anaesthetics
Procaine
Lidocaine under cascade
What farm animals can be masked down?
Small ruminants can use isoflurane under the cascase
What vessel can be used for venous access in farm animals?
Jugular
Tail
Cephalic
Milk
What blocks can be used for local anaesthesia of the head?
Infraorbital
Mental
Cornual
What can you used for local anaesthesia before an ocular operation in the farm animal?
Retrobulbar
Peterson’s
What analgesia can be used for limb surgery in the farm animal?
Perineural infusion
Ring infiltration
IVRA (Bier’s Block)
Bier’s block –> tourniquet around limb then lidocaine administered.
Left on for no more than 2-3 hours. Don’t remove too quickly or get cardiotoxicity (drug returns to heart too quickly).
What local anaesthesia can you use for the caudal body of farm animals?
Epidural
Pudendal
Intra-testicular
What can you use for local anaesthesia of the body of farm animals?
Line block Teat block Inverted L-block Paravertebral block Segemental lumbar epidural block
What are the anaesthetic risks associated with camelids?
Bloat Regurgitation Tympany Salivation Oligate nose-breathers Stomach ulcers
