Ruminant Anesthesia Flashcards
what type of anesthesia do we use with recumbency for ruminants?
- Recumbency with local anesthesia/sedation - not GA
why is general anesthesia less common in adult ruminants?
1.Withdrawal times
2.Due to equipment required
3.Risks of GA without ET intubation
what is the ideal method of anesthesia for ruminants? why
Sedation & Local Anesthesia is Ideal
-less risk of complications (GI, resp, cardiovascular)
-minimal equipment required
-established withdrawl times
Ruminant Anesthesia Disadvantages
Endotracheal intubation
>required with GA
>need ET tubes and skill
Expense of equipment
<inhalational>estimated withdrawl times
</inhalational>
risks of ruminant anesthesia?
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
ruminant age considerations for anesthesia, <2 months
< 2 months
* Immature liver enzyme function until approx. 3 mos
* Benzodiazepines may have prolonged effect
* Prolonged recovery potential
Reversal should be available
cardiovascular concerns for ruminants under GA
- 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
respiratory concerns for ruminants under GA
- 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
GI concerns for ruminants under GA
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
should we use anticholinergics to reduce salivation in ruminants under GA? why?
– –
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
how to position ruminants under GA to reduce salivation complications
occiput elevated, nose positioned down
>reduces aspiration
why is bloat a concen for ruminants under GA?
because ventilation is impeded
regurgitation/ aspiration becomes a higher risk for ruminants under GA if:
– struggling
– light at intubation
– bloat
– not off feed
do ruminants require an endotracheal tube for GA? why?
- 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
pre-anesthetic prep for ruminants
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
fasting guidelines for neonatal ruminants
Fasting 1-2 day old neonatal calf/sheep/goat is not generally recommended
* But ensure last bottle feed >1 hr
fasting guidelines for ruminants 2-4 weeks old
- withhold 1-2 hrs
fasting guidelines for adult ruminants
– Adult Ruminants:
* Food 24 hrs; water 12-18 hrs
– Large bulls:
* Food 24-36 hrs; water 12-18 hrs
properties of xylazine as an induction agent
-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)
when are diazepam or midazolam used as premedicaiton in ruminants? why?
Not routinely used as sedative in adult bovine;
* Ataxia issue
* Minimal calming
Common choice in small ruminants, calves
* Induces moderate sedation
when are diazepam or midazolam used as premedicaiton in ruminants? why?
Not routinely used as sedative in adult bovine;
* Ataxia issue
* Minimal calming
Common choice in small ruminants, calves
* Induces moderate sedation
withdrawl times for xylazine in ruminant
30 days meat; not to be used in lactating animals
what is ketamine used for in ruminants? how do we administer?
premedication is followed by ketamine for induction
-Surgery ≈ 10-15 min duration with xylazine premedication
do we commonly use benzodiazepines in ruminants? why?
Benzodiazepines not as commonly used as long withdrawal
-Xylazine gives the muscle relaxation
-Consider the case
if we use GG plus ketamine for induction, what should we be careful of
Need support for induction
* GG=guaifenesin
* Need <5% as causes hemolysis
most common adult small ruminant induction option? what else is possible?
- Ketamine is the most common
- Propofol and Alfaxalone also possible
if wew use propofol or alfaxalone for small ruminant induction, what do we give prior? what do we give if sick?
– 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
induction options for a calf/lamb/kid <2 weeks old
Mask Inhalant possible
* Little fear of regurgitation if young (monogastric stage)
Propofol or alfaxalone
Ketamine/Benzodiazepine
* Reduced microsomal liver enzyme capacity
* Reversal for benzodiazepine
Calf/Lamb/Kid Induction Options
> 2 weeks
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
what is a ketamine stun and when would we use it? why?
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”
why is ruminant intubation a challenge?
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
airway anatomy of the ruminant that makes ET tube intubation a challenge
- Limited jaw mobility
- Narrow intermandibular space
- Deeply caudal laryngeal opening
- Thick tongue base
- Elongated soft palate
what should we do rapidly after intubation of the ruminant? why?
- 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
basic techniques for ruminant intubation
– Blind Intubation; sheep and calves, mature animal
– Direct Visualization; sheep and calves
– Palpation; mature bovine
maintenance options for ruminant anesthesia
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
how do we monitor depth of anesthesia in ruminants?
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
considerations for ruminant recovery: positioning and reasons for it, airway, extubation?
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!!!
