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