Farm Animal Anaesthesia Flashcards
1
Q
Which sedatives are allowed in food producing animals?
A
- xylazine
- detomidine (bovine/equine)
- azaperone (pig)
2
Q
Which induction agents are allowed in food producing animals?
A
- ketamine
- thiopentone
> EU legislation not UK
3
Q
Which inhalational agent is allowed in food producing animals?
A
- isoflurane (equine) so FA under cascade
4
Q
which local anaesthetics are allowed in food producing animals? Which analgesics?
A
- procaine
- lidcaine
+ various analgesics (NSAIDs, butorphanol etc.)
5
Q
How are majority of GA drugs used in food producing animals?
A
VIa cascade usually from horses (Must be another food producing animal)
*NB: some drugs never allowed in food chain
6
Q
Which procedures in farm animals commonly require GA?
A
- umbilical hernia repair
- urthrostomy
- orthopaedic
- enucleation
7
Q
Which procedures in farm animals can be performed standing?
A
- flank laparotomy
- c-sec
- RDA/LDA
- rumenotomy
- declaw
- dehorning
- teat surgery
- castration
8
Q
Preanaesthetics considerations in ruminants
A
- manual handling and restraint, accurate weight
- regurgitation/aspiration
- salivation
- bloat (tympany)/ruman atony
- hypo/hypertension
- hypoventilation and hypozaemia
- myopathy/neuropathy
- fluid and electrolyte problems
9
Q
2 forms of regurgitation?
A
active (light plane of anaesthesia)
passive (deep plane of anesthesia due to cardia relaxation)
10
Q
How can regurgitation and subsequent pneumonia be minimised? Risks of this?
A
- 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
11
Q
Which induction agent may stimulate salivation? Why is this a problem?
A
ketamine (licensed in FPAs)
- can lead to intubation problems and electrolyte imbalance
12
Q
Treatment of excessive salivation?
A
- atropine (Licensed by EU for equine) BUT never into food chain in UK
13
Q
Why may bloat (tympany) or rumen atony occour under anaesthesia? Prevention?
A
- 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
14
Q
Is hypotension a common problem in ruminants? Tx?
A
Less than horses
- only at deep planes of anaesthesia
- due to high xyalzine doses or ACP (NL)
- Tx as for hroses
15
Q
Define hypertension. Is hypertension common in ruminants? Cause?
A
MAP >200mmHg
- seen in adult bulls and cattle but RARE
- due ^ CO2?
- due to switch sympathetic dominance under GA?
16
Q
How does IPPV differ in ruminants to horses? Why may it be necessary?
A
^ 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
17
Q
How does risk of myopathy/neuropathy differ to horses?
A
- less prone to myopathy
- neuropathy more common
18
Q
What should be expected with a slow recovery in ruminants?
A
- hypomagnesaemia (esp. as many animals being operated on are pregnant)
19
Q
Which sedatives may be used in ruminants, what other effects do these drugs have?
A
> 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
20
Q
What type of drug is ketamine and what effects does it have?
A
- dissociative anaesthetic induction agent
- IV/IM
- excellent analgesic
- muscle rigidity
- laryngeal refelxes remain
- licensed by EU for all food producing species
21
Q
What type of drug is thiopentone and what effects does it have?
A
- 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
22
Q
Which agents are used in ruminants with NO LICENSE?
A
- 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)
23
Q
Which NSAIDs are licensed for use in ruminants?
A
- meloxicam
- flunixin
- ketoprofen
- carprofen
- tolfenamic acid
> see lecture for doses
24
Q
Which opioids are licensed for use in ruminants?
A
NONE - Butorphanol licensed for equine EU so legally allowed under cascade - buprenorphine - morphine/methadone - pethidine .. used but not lic
25
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
26
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)
27
How large an endotracheal tube should be used for ruminants? Anything else required?
- Smaller than for horses
| - stylette and laryngoscope needed for small ruminants
28
WHich local anaesthetics are licensed in ruminants? Which are used?
```
> Lic
- procaine
> EU FPA lic
- benzocaine
- tetracaine
> non-lic cascade
- lidocaine
```
29
What head local blocks can be performed in ruminants?
- infraorbital
- mental
- cornual
- retrobulbar
- peterson's/auriculopalpebral
30
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
31
Which body blocks can be performed on ruminants?
- paravertebral (prox/dist)
- inverted L
- segmental lumbar epidural
- line
- teat
32
Which caudal body/genital blocks can be performed on ruminants?
- epidural
- pudendal
- intra-testicular
33
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
```
34
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
35
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
36
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
```
37
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*
38
Where are majority of injections performed in pig?
- IM (IV too deep due to thick fat)
39
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
40
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
```
41
Which analgesics are licensed in the pig?
NSAIDS
- flunixin (finadyne only)
- ketoprofen
- meloxicam
42
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
```
43
Which maintainance inhalation agents are licensed and used in pigs?
- iso (lic EU FPA)
- sevo (NL)
- des (NL)
44
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
45
IV access points in the pig?
- Ear v. (peripheral, aa. central)
- limbs when asleep
- jugular blind or cut down
- tail
- epigastrics
46
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
47
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)
48
What may trigger malginant hyperthermia episodes in pigs?
- inhalation agents
- caffeine
- suxamethonium
> often fatal
49
Clinical signs of malignant hyperthermia?
- muscle rigidity
- pyrexia sudden onset (>42*)
- sudden ^ CO2 and moisture
50
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
51
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
52
Differences in monitoring ruminants under GA?
- eyes toll down with deepening anaesthesia towards surgical plane
- roll back to a central position when surgically deep
53
Differences in monitoring alpacas under GA?
- retain blink reflex
| - chew or swallow
54
Differences in monitoring pigs under GA?
- retain laryngeal reflex to deeper plane of anaesthesia
