Ruminant Anesthesia Flashcards
How does positioning affect bovine anesthesia?
- dorsal/lateral - decreased FRC
- compression of vena cava - decreased CO
What IV access is commonly used for bovine anesthesia?
- jugular vein
- auricular vein
What unique aspect of bovines require special consideration for anesthesia?
cows are monogastric with large rumen volume = always expect regurgitation, ruminal tympany and bloat due to reduced GI motility, and lots of saliva produced
- significant electrolyte abnormalities
How are bovines prepared for anesthesia?
fasted 12-24 hours minimum (up to 36 hrs) and refrain from water for 8-12 hours
What 3 drugs are commonly used as premeds for bovine anesthesia? What is commonly avoided?
- Xylazine at 1/10 dose used in horses
- Detomidine/Romifidine at a lower dose closer to equine dosage
- Butorphanol or other pure mu agonists
Acepromazine - increases regurgitation and is not particularly useful for sedation
What (bovine) breed differences cause different reactions to Xylazine? When must it be used carefully?
- Brahmans = most sensitive
- Holsteins = least sensitive
final trimester —> can cause premature parturition (usually avoid alpha-2 agonists in last gestation)
How are adult cows and calves induced for anesthesia?
ADULTS - ketamine with either midazolam or guaifenesin
CALVES - propofol, alfaxalone, ketamine, with midazolam (similar to dogs!)
How are bovines intubated? Calves?
direct palpation of arytenoids or palpation with a stylet
nasotracheal or orotracheal with laryngoscope and stylet —> need to avoid aspiration with increased regurgitation and salivation risk
What is an additional way of administering induction in calves?
nasotracheal induction with Xylazine or Diazepam
- this is often enough sedation to proceed with attempting nasotracheal intubation
How are calves nasotracheally intubated?
- use lidocaine KY lube on the tube and nostrils
- pass the tube in the same manner as a stomach tube - ventral and medial
calves will resist most at the initial entrance into the nostril, then relax
What are the 2 major causes of prolonged recovery in calves?
- hypoventilation and high CO2 levels (>70 mmHg)
- hypothermia (<92 F)
(not as common in adults and horses)
Why must bovines be positioned carefully? How can side effects be avoided?
neuropathy and myopathy due to body weight
padding and ropes to keep limbs up
How can regurgitation and salivation be avoided?
- keep larynx high and nose down
- keep patient in the proper plane of anesthesia - too light = regurgitation common
What increases the risk of bloat in anesthetized bovines? How can this be prevented?
increased CV depression and FRC reduction
pass an orogastric rumen tube once intubated
Where is an arterial line most commonly placed in bovines? What are good and bad depth signs?
auricular atery
- GOOD DEPTH = ventromedial eye with no palpebral reflex, no nystagmus
- TOO LIGHT = central eye with palpebral reflex, chewing, regurgitation
Why is ventilation commonly necessary for bovine anesthesia?
rapid, shallow respiration
How is recovery unique in bovines? When are they extubated?
tend to recover nicely, calmly, and smoothly and stand easily on their own
- keep ETT in as patient recovers sternally - can use halter, rope, and hay bales to prop up
- extubate ETT partially inflated to the larynx, then deflate and take out when chewing vigorously
What are the 3 flank blocks typically used for bovine abdominal surgeries?
- line/inverted L block
- proximal para-vertebral block - dorsal and ventral T13, L1, and L2 at their site of emergence from the intervertebral foramen
- distal para-vertebral block - distal ends of L1, L2, and L4 transverse processes
How do sheep and goats compare to bovines? How should they be fasted?
- smaller, easier to handle
- IV catheter easily places for premed and induction
- goats are comparable to dogs
fast from food for 12-20 hrs and water for 6-12 hrs to dry out the rumen and decrease regurgitation risks
What diseases are most commonly seen in sheep?
respiratory disease
(also easily stressed)
What medication yield very good sedation in sheep and goats?
Midazolam
- IM premeds not as commonly used, handleable enough before catheter is places
What family of medications are avoided in sheep? 5 reasons?
alpha-2 agonists
- significant hypoxemia
- vascular congestion
- increases pulmonary artery pressure
- pulmonary edema
- extremely potent
How do alpacas compare to llamas? Camels? What tends to keep them more docile when handled?
- alpacas are generally nicer than llamas
- camels tend to have variable personalities
- all kick and spit well
like to be with their herd —> allow them to remain with their herd when being handled
Why is delivery of IV drugs difficult in camelids? Why must this be done carefully?
no jugular furrow —> palpation beats visualization
close to carotid artery
How are camelids fasted? What is the accuracy of body weight estimations like?
fast from food for 12-18 hr and water for 8-12 hr
often too high —> massive haircoat
How do camelids compare to other ruminants for anesthetic considerations?
only have two forestomachs, but are otherwise very similar to domestic ruminants
- a little less salivation
What is the major difference in premedications in camelids compared to other ruminants? What combination is most commonly used?
camelids require more xylazine than ruminants, but still significantly less than equine patients —> alpacas > llama
Xylazine + Butorphanol IM for sedation
How are camelids induced? What yields poor recovery?
ketamine, telazol, or propofol
alfaxalone
How are camelids intubated? What is especially helpful?
orally/blindly or with a laryngoscope (blade placed on epiglottis to increased visualization of arytenoids)
using a stylet
What is the proper depth in camelids compared to ruminants?
camelids usually will have mild palpebral reflex at the proper surgical plane
