Farm Animal Anaesthesia Flashcards
Which sedatives are allowed in food producing animals?
- xylazine
- detomidine (bovine/equine)
- azaperone (pig)
Which induction agents are allowed in food producing animals?
- ketamine
- thiopentone
> EU legislation not UK
Which inhalational agent is allowed in food producing animals?
- isoflurane (equine) so FA under cascade
which local anaesthetics are allowed in food producing animals? Which analgesics?
- procaine
- lidcaine
+ various analgesics (NSAIDs, butorphanol etc.)
How are majority of GA drugs used in food producing animals?
VIa cascade usually from horses (Must be another food producing animal)
*NB: some drugs never allowed in food chain
Which procedures in farm animals commonly require GA?
- umbilical hernia repair
- urthrostomy
- orthopaedic
- enucleation
Which procedures in farm animals can be performed standing?
- flank laparotomy
- c-sec
- RDA/LDA
- rumenotomy
- declaw
- dehorning
- teat surgery
- castration
Preanaesthetics considerations in ruminants
- manual handling and restraint, accurate weight
- regurgitation/aspiration
- salivation
- bloat (tympany)/ruman atony
- hypo/hypertension
- hypoventilation and hypozaemia
- myopathy/neuropathy
- fluid and electrolyte problems
2 forms of regurgitation?
active (light plane of anaesthesia)
passive (deep plane of anesthesia due to cardia relaxation)
How can regurgitation and subsequent pneumonia be minimised? Risks of this?
- starve 18-24hrs (not ,3mo)
- no water 12 hrs (not 3mo)
> starvation and dehydration -> ketoacidosis? - good depth of anaesthesia when intubating
- good fitting ET tube and properly blown up cuff
- position head so fluids can drain out
- stomach tube
- extubate with cuff still inflated
- put in sternal asap
Which induction agent may stimulate salivation? Why is this a problem?
ketamine (licensed in FPAs)
- can lead to intubation problems and electrolyte imbalance
Treatment of excessive salivation?
- atropine (Licensed by EU for equine) BUT never into food chain in UK
Why may bloat (tympany) or rumen atony occour under anaesthesia? Prevention?
- fermentation continues but cannot eructate
- reduces functional residual capacity and venous return
- pH shift can result in atony
> prevent by adequate starvation and water
> placement of rumen trochar to evacuate gas
Is hypotension a common problem in ruminants? Tx?
Less than horses
- only at deep planes of anaesthesia
- due to high xyalzine doses or ACP (NL)
- Tx as for hroses
Define hypertension. Is hypertension common in ruminants? Cause?
MAP >200mmHg
- seen in adult bulls and cattle but RARE
- due ^ CO2?
- due to switch sympathetic dominance under GA?
How does IPPV differ in ruminants to horses? Why may it be necessary?
^ risk airway damage due to lack of fibrous connective tissue
- often required to manage CO2 levels (drug induced resp depression, chemoreceptor depression, large rumen/bloat -> small TV with minimally ^ rate, v FRC, airway closure and VQ mismatch, v VR and CO
How does risk of myopathy/neuropathy differ to horses?
- less prone to myopathy
- neuropathy more common
What should be expected with a slow recovery in ruminants?
- hypomagnesaemia (esp. as many animals being operated on are pregnant)
Which sedatives may be used in ruminants, what other effects do these drugs have?
> a2 ags: sedation, anxiolytic, recumbence, analgesia, muscle relaxation
- ruminants v sensitive esp. sheep and goats
- xylazine 2% (L), detomidine (L cow)
- side effects:
- pulmonary oedema sheep and goat (xylazine) -> bronchoconstriction (allergy?)
- v eructation
- v swallowing
- ^ urine production
- osmotic diuresis (cf. AVP horses)
- urethral outflow issues
- OT like effect -> uterine contraction
What type of drug is ketamine and what effects does it have?
- dissociative anaesthetic induction agent
- IV/IM
- excellent analgesic
- muscle rigidity
- laryngeal refelxes remain
- licensed by EU for all food producing species
What type of drug is thiopentone and what effects does it have?
- very fast acting induction agent
- no vet licence but licensed by EU for all food producing animals
- very irritant, will cause necrosis, must go IV
- accumulation -> prolonged recoveries
- not for use in thin/debilitated animals
Which agents are used in ruminants with NO LICENSE?
- propofol (v good small ruminants, smooth induction and recovery)
- benzodiazepines (small ruminnats, will sedate neonates and debilitated animals and muscle relax)
- GGE (good centrally acting mm. relaxant)
- Alfaxalone (goat disbudding)
- Chloral hydrate (old drug for sedation/anaesthsia, sedation good, poor for GA)
Which NSAIDs are licensed for use in ruminants?
- meloxicam
- flunixin
- ketoprofen
- carprofen
- tolfenamic acid
> see lecture for doses
Which opioids are licensed for use in ruminants?
NONE - Butorphanol licensed for equine EU so legally allowed under cascade - buprenorphine - morphine/methadone - pethidine .. used but not lic
Which inhalation agents are licensed for use in ruminants?
- isoflurane licensed for equine EU so legally allowed under cascade
- sevoflurane( NL)
- desflurane (NL)
- halothane -> hepatotoxicity (NL)
- mask induction for smaller ruminants
Venous access points in the ruminant?
- jugular (deeper than horse, skin loose in cattle)
- tail vein (beware artery lies next to it!)
- cephalic in small ruminants
- milk vein last resort (risk of thrombophlebitis)
How large an endotracheal tube should be used for ruminants? Anything else required?
- Smaller than for horses
- stylette and laryngoscope needed for small ruminants
WHich local anaesthetics are licensed in ruminants? Which are used?
> Lic - procaine > EU FPA lic - benzocaine - tetracaine > non-lic cascade - lidocaine
What head local blocks can be performed in ruminants?
- infraorbital
- mental
- cornual
- retrobulbar
- peterson’s/auriculopalpebral
Which limb blocks can be performed on ruminants?
- perineural infiltration
- ring infiltration
- IVRA (Bier’s block) using a touniquet
> do not leave on >2 hours
> lidocaine only IV drug usable
> release tournequet slowly
Which body blocks can be performed on ruminants?
- paravertebral (prox/dist)
- inverted L
- segmental lumbar epidural
- line
- teat
Which caudal body/genital blocks can be performed on ruminants?
- epidural
- pudendal
- intra-testicular
Which animals are camelids (alpacas and llamas) like?
> ruminants - 3 compartment stomach, ruminate - prone to bloat/regurge/salivation - lingual torus (tongue) > horses - temperamental - obligate nose breathers - prone to resp obstruction - can develop stomach ulcers with stress
Why is catheter placement often problematic in camelids?
- must be placed high (4cm below angle of jaw)
- or low (rostral to ventral process of C5) * care carotid a. v close*
- tucked under vertebral processes
> blood v. red as evolved to live at altitude so will know if hit artery
What issues are associated with intubating camelids?
- torus linguae and soft palate
- long narrow face
- larynx far back
- sternal and positioning so head down to prevent saliva inhalaiton
- protect eyes from saliva -> ulceration
What drugs can be used in camelids?
> similar to ruminants but mostly NON FPA > sedation - xylazine [no pulmonary oedema seen in camelids cf. ruminants] - benzodiazepines > analgesia - NSAIDs - flunixin - buprenorphine/methodone - nn. blocks/epidural > induction - ketamine - propofol > maintainance - isoflurane - sevoflurane
What special precautions should be taken when ruminants/camelids are recovering?
- sternal
- allow to eructate
- DO NOT REMOVE ET TUBE until fully awake and keep cuff inflated on extubation
- suction prior to extubation
- usually recover quickly*
Where are majority of injections performed in pig?
- IM (IV too deep due to thick fat)
Pre-anaesthetic considerations for pigs?
- vomit so starve at least 6 hours
- handling difficult and prone to stress
- difficult to intubate (may obstruct even with sedation)
- prone to temperature fluctuation and sunburn
- suscpetable to malignant hyperthermia
Which drugs can be used for sedation in pigs?
> azaperone (butyrophenone) LIC - cheap and effective - beware penile prolapse - wait min 20 mins for sedation to take effect > a2s (NL) - may cause vomiting - combo with ket and butorphanol for field anaesthesia > acepromazine (NL) - unpredictable - can ^ heat loss due to vasodilation > benzodiazepines (NL) - midazolam better bioavailability, can be used intranasally for smaller pigs) - not for food animals
Which analgesics are licensed in the pig?
NSAIDS
- flunixin (finadyne only)
- ketoprofen
- meloxicam
Which induction agents are licensed in the pig? Which are used?
> ketamine (lic EU FPA) - after sedation - may need top up > thiopentone (lic EU FPA) - IV only - after sedation > editomidine (NL) > alfaxolone (NL) > propofol (NL) > Mask
Which maintainance inhalation agents are licensed and used in pigs?
- iso (lic EU FPA)
- sevo (NL)
- des (NL)
How is induction practically carried out in the pig?
Extension set - IM needle, stab into neck (poor meat cut)
- inject drug and flush with saline
- pig can run around and not escape you
IV access points in the pig?
- Ear v. (peripheral, aa. central)
- limbs when asleep
- jugular blind or cut down
- tail
- epigastrics
how do pigs larynxes differ to other spp?
- Small
- marked laryngeal reflex (Local spray?)
- need small tube with stylette
- shape of laryngotracheal junction odd, rotate tube 180* once half way in
What environmental factor are pigs particularly susceptable to?
Temperature
- hypothermia esp if small
- malignant hyperthermia (genetic disease also seen in horses, cats, people. Can be tested for)
What may trigger malginant hyperthermia episodes in pigs?
- inhalation agents
- caffeine
- suxamethonium
> often fatal
Clinical signs of malignant hyperthermia?
- muscle rigidity
- pyrexia sudden onset (>42*)
- sudden ^ CO2 and moisture
Tx malignant hyperthermia
- active cooling
- maitain IV fluids to minimise myoglobinurea
- remove trigger (inhalation agent) clean circuit, start TIVA
- ventilate to remove CO2
- bicarbonate to v acidosis
- monitor K+ (hyperkalaemia associated with muscle damage)
- Tx: Dantrolene $$$ prophylactic use best
How does dantrolene work? Side effects?
- reduces Ca release
- only affects striated muscle (minimal smooth and caridac muscle effect)
> side effects - muscle weakness
- sedation
- hepatitis occasionally
- arrythmogenic
Differences in monitoring ruminants under GA?
- eyes toll down with deepening anaesthesia towards surgical plane
- roll back to a central position when surgically deep
Differences in monitoring alpacas under GA?
- retain blink reflex
- chew or swallow
Differences in monitoring pigs under GA?
- retain laryngeal reflex to deeper plane of anaesthesia
