Equine Anaesthesia

Question 1

Give three reasons that horses have a higher rate of mortality with anaesthesia.

Answer 1

Release of catecholamines due to stress - intraoperative cardiac arrest
Post anaesthetic myopathy
Neuropathy and spinal chord malasia - due to poor positioning during surgery

Question 2

Describe post anaesthetic myopathy

Answer 2

• Post anaesthetic myopathy (PAM)  where muscle perfusion has been insufficient during surgery and horse cannot use limbs immediately on recovery resulting in falling and breaking bones. These can sometimes resolve on their own but may result in euthanasia
• Fractures in recovery (due to myopathy)

Question 3

Describe three things that need to be done to prep for equine anaethesia

Answer 3

Place and secure IV cannula
Remove shoes and plait mane and tail
Flush out mouth to remove debris

Question 4

Give three drugs that can be used for premed sedation in horses.

Answer 4

Acepromazine, Alpha 2 agonists, Opioids

Question 5

Describe a demand valve

Answer 5

System that can deliver high O2 levels to the patient without the anaestehtic trolly

Question 6

Describe three induction agent combinations for equine anaesthesia

Answer 6

Alpha 2 agonist and ketamine
Guaiphenesin and ketamine
A benzodiazepine (diazepam or midazolam can be combined with the ketamine)

Question 7

Describe the process of moving a horse from an induction box to theatre

Answer 7

Hobbles applied
Connected to hoist
Moved out of induction box
Head supported
Carefully positioned on padded table
Connected to anaesthesia machine
Receiving sevoflurane in oxygen
Ventilated immediately

Question 8

Describe the maintenance of anaethesia in a horse

Answer 8

Alternatively maintain anaesthesia with inhaled agent (with or without PIVA

Question 9

Describe the manifestations of anaesthetic problems in horses

Answer 9

• Most serious problems occur during maintenance in the horse but only then manifest as problems in recovery!
– Hypotension (low blood pressure)
– Hypoxaemia (low oxygen tension in blood)
– Hypercapnia (high carbon dioxide in blood - changes blood pH)
– Poor positioning

Question 10

Describe spinal chord malacia

Answer 10

Damage to the spinal chord leading to potential paraplegia and death
Affects larger horses (in dorsal recumbancy)
May be caused by bleeding or loss of blood supply to the SC

Question 11

Describe the symptoms of upper airway obstruction in horses

Answer 11

• Stridor or stertor following tracheal extubation
• Nostril flaring on inspiration
• Abdominal respiratory effort
• Exaggerated thoracic excursion
• Absence of airflow at the nostrils
• Obstruction tends to occur within the nasal passages or at the level of the larynx

Question 12

Describe Laryngeal obstruction in horses

Answer 12

• Laryngeal obstruction
• Select appropriate ET tube size and insert gently
• Dorsal displacement of soft palate
• Epiglottic retroversion
• Following laryngeal surgery may leave ET tube in place for recovery (secured appropriately)
• If obstruction occurs be prepared to reintubate (may need more drugs)
• Emergency tracheostomy

Question 13

When would you extubate a horse

Answer 13

When it begins to swallow (be prepared to reintubate if problems with obstructions etc)