Equine Anaesthesia

Question 1

What two types of sedatives (premeds) are used in the horse?

Answer 1

Acepromazine and Alpha 2 agonists

Question 2

How can ACP be administered as a sedative in the horse? What kind of sedation does it give? When should you be careful when using ACP in horses?

Answer 2

IV, IM, Oral gel. It gives limited sedative but is good for shoeing/clipping.
Care when used in breeding stallions (Priapism), hypovolaemia.

Question 3

How can alpha 2 agonists be administered as a sedative in the horse? What alpha 2’s are used in the horse?

Answer 3

IV usually, except detomidine is IM.

Xylazine, detomidine and romifidine.

Question 4

What 4 combinations of drugs could be used for short term TIVA (field anaesthesia) in a horse?

Answer 4

1. Alpha 2, Ketamine +- diazapam
2. Guiaphenesin, Alpha 2, Ketamine (Triple drip)
3. Immobilon (etorphine + ACP)
4. Propofol +- Alpha 2 +- Ketamine

Question 5

How long does a classic triple drip (Guiaphenesin, Alpha 2, Ketamine) give you stable anaesthesia in horses?

Answer 5

Up to 1 hour, good for short procedures.

Question 6

What are some advantages of field anaesthesia with Alpha 2, Ketamine +- diazapam in horses?

Answer 6

Good induction, safe, can top up or infuse, excellent recovery especially if without benzodiazepene)

Question 7

For prolonged GA, why is ACP a desired premed?

Answer 7

Decreases risk of death under GA and decreases amount of volatile agent needed.
Remember BEWARE BREEDING STALLIONS.

Question 8

What injectable induction combinations can be given for prolonged GA? Can they be given after ACP as a premed?

Answer 8

1. Alpha 2, Ketamine +- diazapam
2. Guiaphenesin, Alpha 2, Ketamine (Triple drip)
3. Guiaphenesin + Thiopental/Ketamine
   All can be given after ACP premed

Question 9

Why must you be careful during recovery after inducing with ketamine and maintenance on volatile agents?

Answer 9

It can be very rapid. May need some sedatives to smooth the recovery.

Question 10

What is Giuphenesin? Is it an anaesthestic drug?

Answer 10

No, it is not an anaesthetic drug. It is a centrally acting, long acting muscle relaxant added to a lot of anaesthetic combinations.

Question 11

Why are Propofol and Alfaxalone not practical to be used in the horse?

Answer 11

The amount needed, and the cost.

Question 12

What type of breathing system is used for maintenance in the horse?

Answer 12

Circle or To and Fro

Question 13

What volatile agents can be used for maintenance in the horse? Are they liscensed?

Answer 13

Isoflurane (liscensed), Sevoflurane and Desflurane can be used but not liscensed.

Question 14

What monitors are needed when anaesthetised a horse? (4 that are v. important)

Answer 14

Direct arterial BP, ECG, Capnograph, End tidal agent.

Question 15

How should a horse be positioned under GA in lateral recumbency?

Answer 15

Head raised, don’t overstretch neck or risk of RLN. Under front leg pulled forward, no limbs over abdomen, padding.

Question 16

What are 5 possible anaesthetic complications in horses?

Answer 16

Hypotension, Hypercapnia, Hypoxaemia, Cardiac arrest, Cardiac arrhythmias.

Question 17

Why do horses get hypotension during anaesthesia? How would you improve?

Answer 17

Myocardial depression, Low HR and vasodilation result in hypotension. Improve using +ve inotropes, reducing volatile agent and fliuds.

Question 18

Why do horses get hypercapnia during anaesthesia? How would you improve?

Answer 18

Recumbency and hypoventilation cause a V/Q mismatch. Improve with IPPV.

Question 19

Why do horses get hypoxaemia during anaesthesia? How would you improve?

Answer 19

Recumbency (lungs are squashed) and hypoventilation cause a V/Q mismatch. Improvement is difficult! IPPV, bronchodilator etc. Horses tolerate it relatively well.

Question 20

Why do horses get cardiac arrhythmias during anaesthesia? What serious event can this lead to?

Answer 20

Vagal stimulation may lead to bradycardia. May get tachycardia when toxic or short of fluid. May lead to a cardiac arrest.

Question 21

Why do horses get cardiac arrest during anaesthesia? What is the problem with detecting cardiac arrests in horse? What should you do if this occurs?

Answer 21

High vagal tone and hypotension may lead to cardiac arrest. It is HARD TO DETECT as horse may look like under light sedation and go on breathing, however heart has stopped. Resuscitate ASAP (external cardiac massage and IPPV)