Equine Dr. Bennett

Question 1

Standing vs general anesthesia

Answer 1

many procedures can be perfomed in standing horse

using local nerve blocks & alpha₂ CRI

cheaper, faster & less risk to horse

Question 2

Pre operative assesment

Normal rate?

What is the most common arrhythmia in fit horses?

murmurs?

Answer 2

20-45 bpm

2° AV block - dissapears w/ exercise

very common

Question 3

respiratory system

Answer 3

COPD common in horses > 10 y housed inside

Question 4

What do you need to remember about premedication in horses?

Answer 4

Never anesthetise and unsedated horse!

Question 5

Acepromazine

Answer 5

used in combo w/ other sedatives
oral or injectable

Question 6

indications for Acepromazine

Answer 6

provides some level of tranquilization

cardioprotective

assoicated w/ reduced risk of anesthetic mortality

Question 7

contraindications for Acepromazine

Answer 7

hypovolemic animals

young foals

breeding stallions due to risk of priapism

Question 8

What type of drugs are the mainstays for premedication of adult equines

Answer 8

Alpha₂ adrenoceptor agonists

xylazine

detomidine

romifidine

medetomidine & dexmedetomidine

potent sedative & also analgesics

Question 9

Which Alpha₂ to use, depends on time you need!

Answer 9

Romifidine (>80 min)> Detomidine (≈ 80 min)>Metedetomidine (>60 min)> Xylazine (20 min)

Alpha₂/Alpha₁ selectivity:

Xylazine<detomidine></detomidine>

Detomidine & medetomidine produce greater ataxia

Romificine gives lease analgesia

Question 10

Other drugs used for premed in equines

Answer 10

Opioids

• butorphanol
• morphine
• methadone
• buprenophine

Benzodiazepines

• diazepam
• midazolam

Question 11

What are the side effects of opioids in horses

Answer 11

Decr GI motility

Question 12

What age are benzos predominantly used for

Answer 12

foals < 2 mos of age

for tranquilization

few CV & respiratory effects

Question 13

What are the aims of induction in equine

Which drug helps acheive these aims nicely!

Answer 13

Quiet environment

controlled, slow & gentle

Ketamine!

Question 14

How are equines intubated

Answer 14

usually blindly & oral

but can be nasal

disengage epiglottis from soft palate

Question 15

What is inhalant drug for equines

Answer 15

Isoflurane (only licensed drug)

MAC 1.3% - sx usually requires 20-40% above MAC

Question 16

Equipment used in anes for equines

Answer 16

LA circle system

Vaporizer 4-6% initial

2-3% maintenance

O₂ 6-10 L/min initial

5-10 mL/kg/min maintenace

Question 17

What does TIVA for horses consist of

Answer 17

GG

Alpha₂ agonist (xylazine/detomidine/romifidine)

Ketamine

“Triple drip”

Question 18

What type of ECG setup is used in horses

Answer 18

Lead 1 / Base-Apex

Black = behind left elbow (on PMI)

White = over R jugular furrow

Red = left stifle

Question 19

What arteries are used for art BP?

Answer 19

Dorsal metatarsal

Transverse facial

Question 20

What is goal for MAP in equines

Answer 20

> 70mmHg

important for info on perfusion vs indication of depth of anes.

Question 21

What does pulse oximetry measure?

What is minimum acceptable value?

Answer 21

Hgb saturation

90%

Question 22

How do you monitor depth of anesthesia in equines

Answer 22

Subjectively!

Eye position

• 1 eye central, 1 eye rotated back or forward
• slow palpebral reflex
• lacrimation

anal tone

Question 23

What are signs that equine is too light?

Answer 23

ANY limb movement

ANY swallowing

ANY nystagmus

A moving horse is an awake horse!

Question 24

What are types of pain management drugs in horses

Answer 24

NSAIDs

Alpha2 agonists

Opioids

Regional anesthesia

Epidural anesthesia & analgesia

Intra-articular anesthesia & analgesia

Question 25

NSAIDs for horses

Answer 25

**flunixin** **phenylbutazone**

Question 26

Alpha2 agonists for horses

Answer 26

**CRI** **medetomide/dexmedetomidine** **or** **detomidine** **or** **romifidine**

Question 27

Opioids for horses

Answer 27

**butorphanol** **morphine** **methadone**

Question 28

Common problems during equine anesthesia

Answer 28

**Hypotension** **Hypoventilation** **Hypoxemia** **Recovery**

Question 29

Why does hypotension cause problems

Answer 29

**reduced organ perfusion** **reduced delivery of oxgen to tissues** **incr risk of myopathy**

Question 30

Problems seen with hypoventilation

Answer 30

**leads to respiratory acidosis** **incr risk of hypoxemia** **incr risk of arrhythmias**

Question 31

Problem with hypoxemia

Answer 31

**contributes to diminished oxygen delivery to tissues** **incr risk of myopathy**

Question 32

Problems encountered during recovery

Answer 32

**Myopathy** **Neuropathy** **Spinal cord malacia** **Recovery quality**

Question 33

How to handle common hypotension seen during anes.

Answer 33

1. **Try to reduce vaporizer setting** 2. **incr. fluids** 3. **use vasoactive drug: dobutamine**

Question 34

What defines adequacy of ventilation? How measured? Tx?

Answer 34

**Amount of expired CO₂ ** **Aterial BG/capnograph** **if possible decr anesthetic, use IPPV**

Question 35

What is common cause for hypoxemia in eq anes Prevention? Tx?

Answer 35

**V:Q mismatch** **incr FiO₂** **mechanical ventilation** **Beta2 agonist : salbutamol** **Change position** **reduce pressure from abdominal contents**

Question 36

Prevention of myopathy in equine

Answer 36

**monitor arterial BP & maintain!** **Minimum MAP of 70mmHg**

Question 37

Problems seen in recovery

Answer 37

**excitement/disorientation** **post anesthetic myopathy** **respiratory obstruction** **neurogenic paralysis** **hemorrhagic myelopathy**

Question 38

Important difference between horses & donkeys

Answer 38

**Temperament** * **more stoical & tolerant** **Pharmacokinetics** * **metabolise some drugs more rapidly than horses** * **less sensitive to alpha2 agonists** * **metabolise ketamine more rapidly** * **more sensitive to guaifenesin** - incr risk of resp arrest TIVA: 5% GG + 0.5 ml/mL xylazine + 2mg/mL ketamine 2mL/kg/h approx