Ruminant Anesthesia

Question 1

what type of anesthesia do we use with recumbency for ruminants?

Answer 1

• Recumbency with local anesthesia/sedation - not GA

Question 2

why is general anesthesia less common in adult ruminants?

Answer 2

1.Withdrawal times
2.Due to equipment required
3.Risks of GA without ET intubation

Question 3

what is the ideal method of anesthesia for ruminants? why

Answer 3

Sedation & Local Anesthesia is Ideal

-less risk of complications (GI, resp, cardiovascular)
-minimal equipment required
-established withdrawl times

Question 4

Ruminant Anesthesia Disadvantages

Answer 4

Endotracheal intubation
>required with GA
>need ET tubes and skill

Expense of equipment

<inhalational>estimated withdrawl times
</inhalational>

Question 5

risks of ruminant anesthesia?

Answer 5

WITH UNCONSCIOUSNESS
>Ruminal Distension and Bloat
>Regurgitation & aspiration if not intubated
>Potential to develop neuropathy and myopathy with prolonged recumbency & poor positioning
>Potential development of hypoxemia

Question 6

ruminant age considerations for anesthesia, <2 months

Answer 6

< 2 months
* Immature liver enzyme function until approx. 3 mos
* Benzodiazepines may have prolonged effect
* Prolonged recovery potential

Reversal should be available

Question 7

cardiovascular concerns for ruminants under GA

Answer 7

• hypotension is less - vs. equine or SA
  MBP<60 mmHg not as common unless…

> Dehydrated/sick
Neonate/pediatric age as in all other species
Hypoventilation results in higher PaCO2

Question 8

respiratory concerns for ruminants under GA

Answer 8

• Prone to hypoventilation (fast shallow breaths)
• Small increase in PaCO2 acceptable
• Will require assistance for ventilation once intubated

Hypoventilation results in higher PaCO2, which supports sympathetic tone

Hypoxemia due to:
* GI push on chest and bloat
> V/Q mismatch - Atelectasis
> Prolonged times and dorsal recumbency will promote hypoxemia

– Pulmonary Intravascular Macrophage Degranulation
* “PIMS”
* Small ruminants most typical

– Post xylazine sedation
* See rapid RR
* Poor colour – grey – blanched mucous membranes
* Hypoxemia
* Evidence of Pulmonary edema

– Reversal and support required

Question 9

GI concerns for ruminants under GA

Answer 9

significant!
-salivation
-bloat
-regurgitation, aspiration

Withholding food and water times
-To reduce GI volume and gas producing bacteria, but will still have regurgitation and bloat

Question 10

should we use anticholinergics to reduce salivation in ruminants under GA? why?

Answer 10

– –
Large amounts of salivation
Anticholinergics not indicated to reduce this as
* Reduction in saliva but increased viscosity
* Reduced GI motility with atropine
* Ruminants have Atropinase enzyme

Question 11

how to position ruminants under GA to reduce salivation complications

Answer 11

occiput elevated, nose positioned down
>reduces aspiration

Question 12

why is bloat a concen for ruminants under GA?

Answer 12

because ventilation is impeded

Question 13

regurgitation/ aspiration becomes a higher risk for ruminants under GA if:

Answer 13

– struggling
– light at intubation
– bloat
– not off feed

Question 14

do ruminants require an endotracheal tube for GA? why?

Answer 14

• Mature ruminants-require endotracheal intubation with GA or full unconsciousness
  – To protect airway
  – To provide ventilatory support
• Ruminants -moderately difficult to intubate as they mature

Question 15

pre-anesthetic prep for ruminants

Answer 15

Physical examination +/- blood-work

Appropriate fasting times
* For the age

Organization
* People necessary and sequence of events
> Larger the animal very important
* Equipment
* Anesthetic agents

Question 16

fasting guidelines for neonatal ruminants

Answer 16

Fasting 1-2 day old neonatal calf/sheep/goat is not generally recommended
* But ensure last bottle feed >1 hr

Question 17

fasting guidelines for ruminants 2-4 weeks old

Answer 17

• withhold 1-2 hrs

Question 18

fasting guidelines for adult ruminants

Answer 18

– Adult Ruminants:
* Food 24 hrs; water 12-18 hrs

– Large bulls:
* Food 24-36 hrs; water 12-18 hrs

Question 19

properties of xylazine as an induction agent

Answer 19

-Excellent quality of sedation
* reliable, predictable, dose- dependent
-Reversible
-Analgesic
-Ruminants are more sensitive
* Lower dose compared to equine/SA
-Stabilization to prevent cardiorespiratory side effects
* still best option for sedation in adult
-Withdrawal Time Established
* (3 d meat/ 48 hrs milk)

Question 20

when are diazepam or midazolam used as premedicaiton in ruminants? why?

Answer 20

Not routinely used as sedative in adult bovine;
* Ataxia issue
* Minimal calming

Common choice in small ruminants, calves
* Induces moderate sedation

Question 21

when are diazepam or midazolam used as premedicaiton in ruminants? why?

Answer 21

Not routinely used as sedative in adult bovine;
* Ataxia issue
* Minimal calming

Common choice in small ruminants, calves
* Induces moderate sedation

Question 22

withdrawl times for xylazine in ruminant

Answer 22

30 days meat; not to be used in lactating animals

Question 23

what is ketamine used for in ruminants? how do we administer?

Answer 23

premedication is followed by ketamine for induction
-Surgery ≈ 10-15 min duration with xylazine premedication

Question 24

do we commonly use benzodiazepines in ruminants? why?

Answer 24

Benzodiazepines not as commonly used as long withdrawal
-Xylazine gives the muscle relaxation
-Consider the case

Question 25

if we use GG plus ketamine for induction, what should we be careful of

Answer 25

Need support for induction * GG=guaifenesin * Need <5% as causes hemolysis

Question 26

most common adult small ruminant induction option? what else is possible?

Answer 26

* Ketamine is the most common * Propofol and Alfaxalone also possible

Question 27

if wew use propofol or alfaxalone for small ruminant induction, what do we give prior? what do we give if sick?

Answer 27

– Benzodiazepines, Butorphanol or alpha2-agonist sedation prior – Benzodiazepine of butorphanol if sick – Alpha2-agonist sedation on case by case basis * Avoid if Sick animal * Avoid if history of PIMS on farm

Question 28

induction options for a calf/lamb/kid <2 weeks old

Answer 28

Mask Inhalant possible * Little fear of regurgitation if young (monogastric stage) Propofol or alfaxalone Ketamine/Benzodiazepine * Reduced microsomal liver enzyme capacity * Reversal for benzodiazepine

Question 29

Calf/Lamb/Kid Induction Options > 2 weeks

Answer 29

Sedation: * Xylazine, Diazepam/Midazolam, and or Butorphanol * Remove alpha2-agonist if sick Induction: * Ketamine alone * Diazepam + Ketamine together * Other induction agents can be used such as Propofol or Alfaxalone > not as commonly available to ruminant practitioner

Question 30

what is a ketamine stun and when would we use it? why?

Answer 30

Sub-anesthetic doses of ketamine * For dehorning or castration * With xylazine and/or butorphanol Goal is added safety & reduced struggle for animal and practitioner * Consider supplemental pain medication * Some studies available – be careful to ensure “sub-anesthetic”

Question 31

why is ruminant intubation a challenge?

Answer 31

Anatomy differences: * Poor Jaw mobility – cannot open wide * Large fleshy Tongue – impacts view – in your way * Larynx position-caudal and sloping * Smaller endotracheal tube than expect – If endotracheal tube is too long – easy to intubate the right main stem bronchus

Question 32

airway anatomy of the ruminant that makes ET tube intubation a challenge

Answer 32

* Limited jaw mobility * Narrow intermandibular space * Deeply caudal laryngeal opening * Thick tongue base * Elongated soft palate

Question 33

what should we do rapidly after intubation of the ruminant? why?

Answer 33

* Rapidly over-inflate cuff to reduce chance of aspiration of regurgitated material – Small animal technique takes too long in light animal – After animal stable with less chance of regurgitation, inflate cuff properly if feel have overinflated cuff

Question 34

basic techniques for ruminant intubation

Answer 34

– Blind Intubation; sheep and calves, mature animal – Direct Visualization; sheep and calves – Palpation; mature bovine

Question 35

maintenance options for ruminant anesthesia

Answer 35

Inhalant-preferred for maintenance * Isoflurane or Sevoflurane * Ventilation required as prone to > hypoventilation * MAC levels same for ruminants as in other species Triple Drip Mixtures Alpha2-agonist/Ketamine additional doses * >1 month Propofol or Alfaxalone additional doses or TIVA * Small ruminants

Question 36

how do we monitor depth of anesthesia in ruminants?

Answer 36

Palpebral reflex maintained * Ocular rotation classic Muscle Tone, Movement * Esophageal movement when light > Reflux starting * Shivering Respiratory System * RR and depth, SPO2, ETCO2, Blood gases Cardiovascular System * HR, ECG, BP

Question 37

considerations for ruminant recovery: positioning and reasons for it, airway, extubation?

Answer 37

Place in sternal - Examine Airway: Remove Debris Reduce atelectasis by * Returning to sternal / sighing (ruminant) * Waiting for eructation Maintain Airway until they can maintain sternal and strong swallowing reflex Extubate with cuff partially to fully inflated Ruminants are very calm and smart!!!