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Principles of Science BVetMed 3 > Farm animal and camelid anaesthesia > Flashcards

Farm animal and camelid anaesthesia Flashcards

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1
Q

What are some examples of surgeries do you need a GA for?

A
  • umbilical hernia repair
  • urethrostomy
  • orthopaedic (not all)
  • enucleation (depends on species)
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2
Q

Give some examples of surgeries you can use a sedation and local anaesthetic technique

A
  • flank laparotomy
  • csection
  • RDA or LDA
  • rumenotomy
  • declaw
  • dehorning
  • teat surgery
  • castration
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3
Q

List pre-anaesthetic considerations for ruminants - 8

A
  • handling, restrain, accurate weight
  • regurgitation/aspiration
  • salivation
  • bloat (tympany)/rumen atony
  • hypotension/hypertension
  • hypoventilation and hypoxaemia
  • myopathy/neuropathy
  • fluid and electrolyte problems
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4
Q

Outline regurgitation as a consequence of anaesthesia in ruminants

A

Can lead to aspiration pneumonia which can be fatal

  • ACTIVE - light plane of anaesthesia (commonly at intubation)
  • PASSIVE - deep anaesthesia (cardia relaxation)
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5
Q

How can you reduce the risk of regurgitation in ruminants? 6

A
  • 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
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6
Q

How does ketamine affect salivation?

A
  • 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)
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7
Q

Why do you get bloat (tympany)/ rumen atony with with anaesthesia?

A

no eructation when anaesthetised –> reduces FRC and venous return –> continued fermentation can lead to pH shift and atony

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8
Q

How can you prevent bloat (tympany)/ rumen atony with anaesthesia? 2

A
  • adequate starvation and water withholding time

- placement of a rumen tube or trochar to evacuate gas

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9
Q

Describe hypotension in ruminants under GA

A
  • much less likely compared to horses
  • deep planes of anaesthesia
  • high xylazine doses or use of ACP (NL) implicated
  • support required
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10
Q

What might cause hypertension in adult bulls and cattle under GA? (2 theories)

A
  • 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
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11
Q

Why are ruminants more prone to airway damage during IPPV?

A

less fibrous connective dtissue

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12
Q

Why does hypoventilation and hypoxaemia occur in GA ruminants? 3

A
  • 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).
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13
Q

Outline the likelihood of myopathy and neuropathy in ruminants under GA versus horses?

A

Ruminants are less prone to myopathy but neuropathy is more common.
AVOID BY: positioning, padding, ABP, oxygenation and perfusion

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14
Q

What sedative is used in ruminants?

A

ALPHA 2 AGONISTS –> sedation, anxiolysis, recumbency, analgesia, mm relaxation. Ruminants are very sensitive to these (esp. sheep and goats). Xylazine and detomidine (L-cow)

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15
Q

What are the side effects of alpha 2 agonists in ruminants? 7

A
  • 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
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16
Q

What can be used for induction in ruminants? 2

A

Ketamine or thiopentone

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17
Q

Properties - induction with ketamine in ruminants - 4

A
  • dissociative anaesthetis (use IV or IM)
  • excellent analgesic
  • mm rigidity
  • laryngeal reflexes remain
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18
Q

Properties - induction with thipentane in ruminants - 5

A
  • 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
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19
Q

Are there any injectable agents for induction in ruminants?

A

No (but they include propofol, benzodiazepines, GCE, alphaxalone, chloral hydrate)

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20
Q

What is propofol good for?

A

Injectable induction of small ruminants as smooth induction and recovery. NOT LICENSED.

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21
Q

What are benzodiazepines good for?

A

Injectable induction. small ruminants, sedate neonates and debilitated animals well. NOT LICENSED

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22
Q

What is GCE good for?

A

Injectable induction. good centrally acting mm relaxant. NOT LICENSED

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23
Q

What is alfaxalone good for?

A

Injectable induction. used for goat disbudding. NOT LICENSED

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24
Q

What is chloral hydrate good for?

A

Injectable induction. old drug for sedation/anaesthesia. sedation acceptable, poor for GA. NOT LICENSED.

25
Q

What are the 2 main ways or providing analgesia in ruminants?

A
  • ** NSAIDs (licensed - meloxicam, flunixin, ketoprofen, carprofen, tolfenamic acid)***
  • OPIODIS (NL in UK, include butorphanol, buprenorphine, morphine/methadone, pethidine)
26
Q

Name 4 inhalation agents used in ruminants

A
  • Isoflurane (licensed)
  • Sevoflurane (NL)
  • Desflurane (NL)
  • Halothane (NL) - hepatotoxicity
27
Q

How can you anaesthetise smaller ruminants?

A

you ca mask them down

28
Q

What are your venous access options in ruminants?

A
  • JUGULAR - deeper than horse
  • TAIL VEIN - often artery is used
  • CEPHALIC - small ruminants
  • MILK VEIN - don’t use unless nothing left
29
Q

What do you need to consider when intubating ruminants?

A

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.

30
Q

What can be used for local anaesthesia in ruminants?

A

LICENSED: procaine, benzocaine, tetracaine
NOT LICENSED: lidocaine
DOSES vary depending on toxicity. Sheep and goats are quite susceptible.

31
Q

Which nerves might be blocked for local anaesthesia? 5

A
  • Infraorbital
  • mental
  • cornual
  • retrobullar
  • Peterson’s/ Auriculopalpebral
32
Q

Name 3 methods for local anaesthesia of ruminant limbs

A
  • Peineural infiltration
  • ring infiltration
  • IVRA (Bier’s Block)
33
Q

Name 5 methods for local anaesthesia of ruminant body

A
  • paravertebral block (distal/proximal)
  • inverted L-block
  • segmental lumbar epidural block
  • line block
  • teat block
34
Q

Name 3 methods for local anaesthesia of ruminant genitalia

A
  • epidural
  • pudendal block
  • intra-testicular
35
Q

What are the specific considerations for camelids (alpacas and llamas)? 8

A
  • 3 compartment stomach (ruminate)
  • prone to bloat / regurgitation/ salivation
  • projectile regurgitation possible
  • lingual torus
  • temperamental behaviour, often placcid
  • obligate nose breathers
  • more prone to respiratory obstruction
  • can develop C3 stomach ulcers with stress
36
Q

Why is catheter placement in camelids problematic?

A

Has to either really high or low in neck:
HIGH - 4cm below angle of jaw
LOW - rostral to ventral process of C5 but care of carotid.

37
Q

Why is it hard to differentiate camelid venous and arterial blood?

A

Both very red due to altitude adaptation.

38
Q

Why is camelid intubation problematic?

A
  • torus lingae and soft palate
  • long narrow face
  • larynx relatively far back
  • sternal and positioning
39
Q

What should you do with camelid (hyper)salivation? 3

A
  • head down
  • suction
  • protect eyes (ulceration)
40
Q

Name 2 drugs that can be used to sedate camelids.

A

Like ruminants.

Xylazine and benzodiazepine

41
Q

Name 3 drugs that can be used to provide analgesia for camelids

A
  • NSAIDs - flunixin
  • Buprenorphine/Methadone
  • Nerve blocks/epidural
42
Q

Name 2 drugs used for induction in camelids

A
  • ketamine

- propofol

43
Q

Name 2 drugs used for maintenance in camelids

A
  • isolfurane

- sevoflurane

44
Q

Outline recovery for camelids

A

ideally in sternal recumbency - allow head to rotate down for drainage from time to time. should eructate. don’t remove ETT until can remain like this - keep cuff INFLATED to protect airway. extubate with cuff inflated, suction prior to extubation. recovery is usually quite quick.

45
Q

What are the main problems when anaesthetising pigs - 8

A
  • IV access difficult so go IM first
  • thick fat layer so long needles
  • handling difficult and prone to stress
  • very strong and potentially dangerous
  • can vomit so starve for at least 6 hours, water from pre-medication onwards
  • difficult to intubate
  • prone to temperature fluctuation (hypothermia) and sunburn
  • susceptible to Malignant Hyperthermia (MH)
46
Q

What drug is usually used to sedate pigs?

A
  • **Azaperone (Buytrophenone) - licensed for this. cheap and effective, can cause penile prolapse in boars. Wait minimum 20 minutes for sedation to take affect.
  • Other NL options include: alpha 2s, acepromazine and benzodiazepines
47
Q

How can analgesia be provided to pigs?

A

Licensed NSAIDs - flunixin, ketoprofen and meloxicam

48
Q

What drugs are usually used to perform induction in pigs?

A
  • ** Ketamine or thipentone (both licensed).***
  • Ketamine - give after sedation, may need top up
  • Thiopentone - after sedation, IV only
  • OTHERS - etomidate, alphaxalone, propofol, mask
49
Q

How can anaesthesia be maintained in pigs?

A
  • ** Isoflurane (licensed) ***

- Also sevoflurane or desflurane (neither are licensed)

50
Q

Where should you give an IM injection in the pig?

A

Neck (poorer meat mm here)

51
Q

Which veins can you use for IV access in the pig?

A
  • ear (whens sedated or restrained)
  • limb (when asleep)
  • jugular (blind or cut down)
  • tail
  • epigastric
52
Q

Why is ET intubation difficult in pigs? How do you do it?

A

WHY DIFFICULT: small cricothyroid junction, marked laryngeal reflexes (LA spray?)
HOW: need small tubes with stylette, visual method with laryngoscope, small pigs to be kept in sternal recumbency, (down then up) technique due to shape of laryngotracheal gunction

53
Q

What does MH stand for?

A

Malignant Hyperthermia or Malignant Hyperpyrexia (MH or MHP) in pigs.

54
Q

What causes MH?

A 
MH = an autosomal dominant gene implicated
Also RYR1 (ryanodine receptor gene) implicated. Overall effect of a fault in the RYR1 gene is decreased activation threshold and much increased deactivation threshold to calcium --> clinical signs (ATP depletion (Ca pumps) --> mm rigidity) and temperatures of 42 degrees +
55
Q

What agents can cause MH to trigger with an often fatal consequence? 3

A

Halothane or other inhalant agents, caffeine or suxamethonium

56
Q

Treatment - MH in pigs - 11

A
  • Remove drug (causing the MH)
  • Treat the hyperthermia:
  • active cooling
  • maintain IV fluids to minimise renal insult (myoglobinuria)
  • remove trigger (totally clean circuit, ideally non-rebreathing)
  • ventilate to reduce CO2
  • (bicarbonate to reduce acidosis)
  • (monitor K+ to avoid hyperkalaemia - damaged mm)
  • Dantrolene (drug that reduces Ca release, prophylactic use better)
  • don’t use inhalants or depolarising neuromuscular blockade
  • can test for it
57
Q

What are the adverse effects of dantrolene (used to treat MH in pigs)? 4

A
  • mm weakness
  • sedation
  • hepatitis (occasional)
  • arrhythmias
58
Q

What are the main differences with ruminants in terms of monitoring? 3

A
  • ruminant eyes tend to roll down with deepening anaesthesia towards a surgical plane rotating back to a central position when centrally deep
  • alpacas may still retain a blink reflex and may also chew or swallow
  • pigs may retain a laryngeal reflex until a deeper plane of anaesthesia.

Principles of Science BVetMed 3 (110 decks)

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