Equine anaesthesia

Question 1

What pre-med is commonly used in horses

Answer 1

ACP
Alpha2 agonist and opiate IV

Question 2

When might we avoid using ACP in equine anaesthesia

Answer 2

In shock colic cases due to already being vasodilated

Question 3

Which opiate do we usually use in equine pre-meds and when might we change this

Answer 3

Usually butorphanol; this has more of a sedative effect rather than pain relief
If very painful can use morphine (but generally don’t use this due to risk of ileus)

Question 4

How much sedation do we use for pre-med for GA compared with for standing sedation procedures

Answer 4

Double

Question 5

What do we use at induction in equine GA

Answer 5

Ketamine IV
Also add in midazolam to counteract the muscle rigidity caused by ketamine

Question 6

Methods of induction

Answer 6

Free fall
Assisted 1 person
Crush with/without door
Flop

Question 7

How do we encourage a horse to fall during assisted one person induction

Answer 7

Hold the head up; pull on head and push on shoulder to direct them to fall away from you

Question 8

How do we maintain anaesthesia in the field

Answer 8

Ketamine top ups every 10 minutes using one third to half of an induction dose
Can add more alpha 2 agonist if this starts to wear off

Question 9

How do we maintain anaesthesia in the hospital

Answer 9

Using isoflourane
Circle breathing system

Question 10

Monitoring anaesthesia in the field under ketamine maintenance

Answer 10

Difficult since ketamine causes dissociation
Animals can look relatively awake with central eye, blink, irregular breathing and nystagmus
Increased muscle tone may indicate lightening plane

Question 11

How to monitor anaesthesia plane under isoflourane

Answer 11

Want eyes to be medial NOT central
If nystagmus is seen, this means the animal is very light
Increasing blood pressure is a better indicator of lightening plane vs HR/RR

Question 12

What is the aim of blood pressure maintenance during equine GA

Answer 12

Keep MAP over 70mmHG to avoid underperfucion of muscles and spinal cord leadin to ataxia

Question 13

General rule for how long recovery should take

Answer 13

20 mins + extra 20 mins for every hour under anaesthesia

Question 14

What transition occurs when tube is removed and how can we try and make sure this is safe

Answer 14

From tube breathing to obligate nasal breathing
Involves movement of soft palate back into position; via swallowing
So remove the tube once the horse can swallow

Question 15

What neuropathies might we see following equine GA and how can we avoid this

Answer 15

Radial nerve compression of lower leg when lying in lateral; should pull lower leg as far forward as possible

Facial nerve neuropathy from buckles on head collar

Question 16

What is spinal cord malacia

Answer 16

Complication of GA sometimes seen in young large heavy breed horses when lying directly on back

Key sign on recovery = dog sitting
= complete paralysis from lumbar area down

Question 17

What factors increase the risk of fractures during recovery

Answer 17

Myopathy
Underlying stress fractures in race horses
Peri-parturient mares at higher risk

Question 18

What recumbency should we recover horses in

Answer 18

If operation done in lateral then recover them in same recumency as op done to avoid compressing the only non-collapsed lung