Equine Anesthesia

Question 1

What are 2 common arrhythmias in horses?

Answer 1

Atrial fibrillation and 2nd degree AV block

Question 2

Which of the following is a pathologic arrhythmia in a horse?

Atrial fibrillation
2nd degree AV block

Answer 2

Atrial fibrillation

Question 3

What causes a 2nd degree AV block in a horse?

Answer 3

High vagal tone

Question 4

What are common respiratory pathologies in horses?

Answer 4

COPD, dorsal displacement of soft palate, laryngeal hemiplegia

Question 5

How do you dose drugs for obese equine patients?

Answer 5

Based on ideal body condition

Question 6

What size ET tube is needed for the average equine patient (400-500 kg)?

Answer 6

26 mm (have a 24 mm available as well)

Question 7

What size ET tube is needed for a large draft horse (>500 kg)?

Answer 7

30 mm

Question 8

What size ET tube is needed for a donkey?

Answer 8

14-16 mm

Question 9

True/False: a laryngoscope is needed for equine intubation

Answer 9

False, intubation is blind

Question 10

What are the possible methods of maintenance for equine anesthesia?

Answer 10

1) Inhalant anesthesia alone; 2) inhalant anesthesia w/ PIVA; 3) TIVA

Question 11

What is the approximate blood volume of an adult horse? Of a foal?

Answer 11

~8% BW (kg). ~9% BW

Question 12

Which of the following is the correct mean arterial pressure to maintain in an equine patient?

>25 mmHg
>40 mmHg
>70 mmHg
>80 mmHg
>100 mmHg

Answer 12

> 70 mmHg (SAP >90-100 mmHg)

Question 13

Which of the following is the correct range for ETCO2 and PaCO2 to be maintained in an equine patient?

35-50 mmHg
50-65 mmHg
20-30 mmHg
60-75 mmHg

Answer 13

35-50 mmHg (ETCO2 may be 10-15 mmHg lower)

Question 14

True/False: if an equine patient is on 100% oxygen, its PaO2 should be at least >200 mmHg

Answer 14

True!

Question 15

What is an ideal PaO2 for an equine patient on 100% oxygen?

Answer 15

FiO2 x 5 = 500 mmHg

Question 16

Where do the electrodes go on the horse for the base apex lead system?

Answer 16

Right arm electrode (white) –> cranial to the right scapula in right jugular furrow (“cold shoulder”)
Left arm electrode (black) –> over the apex beat on the left side, level w/ the olecranon (“black heart”)
Left leg electrode (red) –> caudal to black lead

Question 17

How can you measure anesthetic depth of an equine patient?

Answer 17

Eyes, muscle tightness in shoulders and neck

Question 18

When at the appropriate depth of anesthesia, what should you see w/ the equine eye?

Answer 18

Ventromedial to central w/ medium sized pupil, minimal to no palpebral reflex, slowed corneal reflex

Question 19

What do nystagmus and lacrimation indicate about anesthetic depth of an equine patient?

Answer 19

Nystagmus = very, very light
Lacrimation = light plane

Question 20

What are some premeds we can use with an equine patient?

Answer 20

Acepromazine (0.005-0.03 mg/kg) –> as adjunct to other sedatives
Xylazine (0.5-1.0 mg/kg IV; 1-2 mg/kg IM)
Detomidine (5-20 ug/kg IV; 20-40 ug/kg IM)
Romifidine (80-120 ug/kg IV or IM)
Butorphenol (0.01-0.05 mg/kg IV)
Morphine (0.05-0.1 mg/kg IV slowly)

Question 21

What is a possible complication when using Acepromazine in equine patients?

Answer 21

Potential for penile prolapse –> caution when using w/ breeding stallions

Question 22

What is a possible complication when using Opioids (Butorphanol/Morphine) in equine patients?

Answer 22

May cause excitement w/o other sedatives

Question 23

What type of drugs can you use as a premed in foals?

Answer 23

Benzodiazepines

Question 24

Which of the following is the correct pairing of MAC to gas for an equine patient?

Iso = 1.3, Sevo = 2.3
Iso = 2.3, Sevo = 1.3
Iso = 1.31, Sevo = 2.31
Iso = 2.6, Sevo = 4.6

Answer 24

Iso = 1.31, Sevo = 2.31

Question 25

True/False: if using TIVA for maintenance anesthetic in an equine patient, you can keep them under indefinitely.

Answer 25

False. Maximum 90 min if using TIVA

Question 26

What are possible CV complications of anesthesia in a horse?

Answer 26

Hypotension (MAP >70 –> higher mean required to maintain muscle perfusion)
2nd degree AV block
Hemorrhage

Question 27

How would you resolve hypotension in an equine patient?

Answer 27

Decrease inhalant (vasodilation) --> CRI, local blocks
Increase fluids --> isotonic, colloids
Positive inotropes --> dobutamine CRI

Question 28

How would you resolve 2nd degree AV block in an equine patient?

Answer 28

Dobutamine, alpha-2 agonists

Question 29

What are possible pulmonary complications of anesthesia in a horse?

Answer 29

Hypercapnea, hypoxemia

Question 30

What affect do inhalants have on hypoxic pulmonary vasoconstriction (HPV)?

Answer 30

They decrease HPV

Question 31

What are the 4 ways we minimize pulmonary complications in equine anesthesia?

Answer 31

1) Minimize inhalants by using CRI, local blocks, and adequate premeds
2) Provide mechanical ventilation w/ PEEP
3) Provide 100% oxygen even in the field
4) Minimize duration of procedure

Question 32

What are some complications of recovery in equine anesthesia?

Answer 32

Neuropathy, myopathies, nasal edema, laryngeal dysfunction, dorsal displacement of soft palate, hypoxemia, traumatic injury

Question 33

How do we treat nasal edema, and why is it a major problem?

Answer 33

Phenylephrine in the nostrils, nasotracheal intubation. Horses are obligate nasal breathers.

Question 34

What are 2 causes of laryngeal dysfunction?

Answer 34

Preexisting hemiplegia, recurrent laryngeal nerve damage during recumbency

Question 35

Which of the following is the correct amount of oxygen to give a horse to treat hypoxemia during recovery?

10 L/min
35 L/min
15 L/min
20 L/min

Answer 35

15 L/min. Oxygen should be given with a demand valve via ET tube until the horse is extubated