Farm animal and camelid anaesthesia

Question 1

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

Answer 1

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

Question 2

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

Answer 2

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

Question 3

List pre-anaesthetic considerations for ruminants - 8

Answer 3

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

Question 4

Outline regurgitation as a consequence of anaesthesia in ruminants

Answer 4

Can lead to aspiration pneumonia which can be fatal

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

Question 5

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

Answer 5

• 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

Question 6

How does ketamine affect salivation?

Answer 6

• 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)

Question 7

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

Answer 7

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

Question 8

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

Answer 8

• adequate starvation and water withholding time

- placement of a rumen tube or trochar to evacuate gas

Question 9

Describe hypotension in ruminants under GA

Answer 9

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

Question 10

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

Answer 10

• 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

Question 11

Why are ruminants more prone to airway damage during IPPV?

Answer 11

less fibrous connective dtissue

Question 12

Why does hypoventilation and hypoxaemia occur in GA ruminants? 3

Answer 12

• 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).

Question 13

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

Answer 13

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

Question 14

What sedative is used in ruminants?

Answer 14

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

Question 15

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

Answer 15

• 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

Question 16

What can be used for induction in ruminants? 2

Answer 16

Ketamine or thiopentone

Question 17

Properties - induction with ketamine in ruminants - 4

Answer 17

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

Question 18

Properties - induction with thipentane in ruminants - 5

Answer 18

• 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

Question 19

Are there any injectable agents for induction in ruminants?

Answer 19

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

Question 20

What is propofol good for?

Answer 20

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

Question 21

What are benzodiazepines good for?

Answer 21

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

Question 22

What is GCE good for?

Answer 22

Injectable induction. good centrally acting mm relaxant. NOT LICENSED

Question 23

What is alfaxalone good for?

Answer 23

Injectable induction. used for goat disbudding. NOT LICENSED

Question 24

What is chloral hydrate good for?

Answer 24

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

Question 25

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

Answer 25

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

Question 26

Name 4 inhalation agents used in ruminants

Answer 26

* Isoflurane (licensed) - Sevoflurane (NL) - Desflurane (NL) - Halothane (NL) - hepatotoxicity

Question 27

How can you anaesthetise smaller ruminants?

Answer 27

you ca mask them down

Question 28

What are your venous access options in ruminants?

Answer 28

- JUGULAR - deeper than horse - TAIL VEIN - often artery is used - CEPHALIC - small ruminants - MILK VEIN - don't use unless nothing left

Question 29

What do you need to consider when intubating ruminants?

Answer 29

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.

Question 30

What can be used for local anaesthesia in ruminants?

Answer 30

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

Question 31

Which nerves might be blocked for local anaesthesia? 5

Answer 31

- Infraorbital - mental - cornual - retrobullar - Peterson's/ Auriculopalpebral

Question 32

Name 3 methods for local anaesthesia of ruminant limbs

Answer 32

- Peineural infiltration - ring infiltration - IVRA (Bier's Block)

Question 33

Name 5 methods for local anaesthesia of ruminant body

Answer 33

- paravertebral block (distal/proximal) - inverted L-block - segmental lumbar epidural block - line block - teat block

Question 34

Name 3 methods for local anaesthesia of ruminant genitalia

Answer 34

- epidural - pudendal block - intra-testicular

Question 35

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

Answer 35

- 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

Question 36

Why is catheter placement in camelids problematic?

Answer 36

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.

Question 37

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

Answer 37

Both very red due to altitude adaptation.

Question 38

Why is camelid intubation problematic?

Answer 38

- torus lingae and soft palate - long narrow face - larynx relatively far back - sternal and positioning

Question 39

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

Answer 39

- head down - suction - protect eyes (ulceration)

Question 40

Name 2 drugs that can be used to sedate camelids.

Answer 40

Like ruminants. | Xylazine and benzodiazepine

Question 41

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

Answer 41

- NSAIDs - flunixin - Buprenorphine/Methadone - Nerve blocks/epidural

Question 42

Name 2 drugs used for induction in camelids

Answer 42

- ketamine | - propofol

Question 43

Name 2 drugs used for maintenance in camelids

Answer 43

- isolfurane | - sevoflurane

Question 44

Outline recovery for camelids

Answer 44

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.

Question 45

What are the main problems when anaesthetising pigs - 8

Answer 45

- 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)

Question 46

What drug is usually used to sedate pigs?

Answer 46

* **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

Question 47

How can analgesia be provided to pigs?

Answer 47

Licensed NSAIDs - flunixin, ketoprofen and meloxicam

Question 48

What drugs are usually used to perform induction in pigs?

Answer 48

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

Question 49

How can anaesthesia be maintained in pigs?

Answer 49

* ** Isoflurane (licensed) *** | - Also sevoflurane or desflurane (neither are licensed)

Question 50

Where should you give an IM injection in the pig?

Answer 50

Neck (poorer meat mm here)

Question 51

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

Answer 51

- ear (whens sedated or restrained) - limb (when asleep) - jugular (blind or cut down) - tail - epigastric

Question 52

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

Answer 52

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

Question 53

What does MH stand for?

Answer 53

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

Question 54

What causes MH?

Answer 54

``` 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 + ```

Question 55

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

Answer 55

Halothane or other inhalant agents, caffeine or suxamethonium

Question 56

Treatment - MH in pigs - 11

Answer 56

- 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

Question 57

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

Answer 57

- mm weakness - sedation - hepatitis (occasional) - arrhythmias

Question 58

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

Answer 58

- 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.