Ruminant Anesthesia

Question 1

How does positioning affect bovine anesthesia?

Answer 1

• dorsal/lateral - decreased FRC
• compression of vena cava - decreased CO

Question 2

What IV access is commonly used for bovine anesthesia?

Answer 2

• jugular vein
• auricular vein

Question 3

What unique aspect of bovines require special consideration for anesthesia?

Answer 3

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

Question 4

How are bovines prepared for anesthesia?

Answer 4

fasted 12-24 hours minimum (up to 36 hrs) and refrain from water for 8-12 hours

Question 5

What 3 drugs are commonly used as premeds for bovine anesthesia? What is commonly avoided?

Answer 5

1. Xylazine at 1/10 dose used in horses
2. Detomidine/Romifidine at a lower dose closer to equine dosage
3. Butorphanol or other pure mu agonists

Acepromazine - increases regurgitation and is not particularly useful for sedation

Question 6

What (bovine) breed differences cause different reactions to Xylazine? When must it be used carefully?

Answer 6

• Brahmans = most sensitive
• Holsteins = least sensitive

final trimester —> can cause premature parturition (usually avoid alpha-2 agonists in last gestation)

Question 7

How are adult cows and calves induced for anesthesia?

Answer 7

ADULTS - ketamine with either midazolam or guaifenesin

CALVES - propofol, alfaxalone, ketamine, with midazolam (similar to dogs!)

Question 8

How are bovines intubated? Calves?

Answer 8

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

Question 9

What is an additional way of administering induction in calves?

Answer 9

nasotracheal induction with Xylazine or Diazepam

• this is often enough sedation to proceed with attempting nasotracheal intubation

Question 10

How are calves nasotracheally intubated?

Answer 10

• 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

Question 11

What are the 2 major causes of prolonged recovery in calves?

Answer 11

1. hypoventilation and high CO2 levels (>70 mmHg)
2. hypothermia (<92 F)

(not as common in adults and horses)

Question 12

Why must bovines be positioned carefully? How can side effects be avoided?

Answer 12

neuropathy and myopathy due to body weight

padding and ropes to keep limbs up

Question 13

How can regurgitation and salivation be avoided?

Answer 13

• keep larynx high and nose down
• keep patient in the proper plane of anesthesia - too light = regurgitation common

Question 14

What increases the risk of bloat in anesthetized bovines? How can this be prevented?

Answer 14

increased CV depression and FRC reduction

pass an orogastric rumen tube once intubated

Question 15

Where is an arterial line most commonly placed in bovines? What are good and bad depth signs?

Answer 15

auricular atery

• GOOD DEPTH = ventromedial eye with no palpebral reflex, no nystagmus
• TOO LIGHT = central eye with palpebral reflex, chewing, regurgitation

Question 16

Why is ventilation commonly necessary for bovine anesthesia?

Answer 16

rapid, shallow respiration

Question 17

How is recovery unique in bovines? When are they extubated?

Answer 17

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

Question 18

What are the 3 flank blocks typically used for bovine abdominal surgeries?

Answer 18

1. line/inverted L block
2. proximal para-vertebral block - dorsal and ventral T13, L1, and L2 at their site of emergence from the intervertebral foramen
3. distal para-vertebral block - distal ends of L1, L2, and L4 transverse processes

Question 19

How do sheep and goats compare to bovines? How should they be fasted?

Answer 19

• 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

Question 20

What diseases are most commonly seen in sheep?

Answer 20

respiratory disease

(also easily stressed)

Question 21

What medication yield very good sedation in sheep and goats?

Answer 21

Midazolam

• IM premeds not as commonly used, handleable enough before catheter is places

Question 22

What family of medications are avoided in sheep? 5 reasons?

Answer 22

alpha-2 agonists

1. significant hypoxemia
2. vascular congestion
3. increases pulmonary artery pressure
4. pulmonary edema
5. extremely potent

Question 23

How do alpacas compare to llamas? Camels? What tends to keep them more docile when handled?

Answer 23

• 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

Question 24

Why is delivery of IV drugs difficult in camelids? Why must this be done carefully?

Answer 24

no jugular furrow —> palpation beats visualization

close to carotid artery

Question 25

How are camelids fasted? What is the accuracy of body weight estimations like?

Answer 25

fast from food for 12-18 hr and water for 8-12 hr

often too high —> massive haircoat

Question 26

How do camelids compare to other ruminants for anesthetic considerations?

Answer 26

only have two forestomachs, but are otherwise very similar to domestic ruminants

• a little less salivation

Question 27

What is the major difference in premedications in camelids compared to other ruminants? What combination is most commonly used?

Answer 27

camelids require more xylazine than ruminants, but still significantly less than equine patients —> alpacas > llama

Xylazine + Butorphanol IM for sedation

Question 28

How are camelids induced? What yields poor recovery?

Answer 28

ketamine, telazol, or propofol

alfaxalone

Question 29

How are camelids intubated? What is especially helpful?

Answer 29

orally/blindly or with a laryngoscope (blade placed on epiglottis to increased visualization of arytenoids)

using a stylet

Question 30

What is the proper depth in camelids compared to ruminants?

Answer 30

camelids usually will have mild palpebral reflex at the proper surgical plane