3. Clinical induction and maintenance

Question 1

List considerations made when choosing induction and maintenance agents

Answer 1

Legal requirements
a.	Licensing cascade
Pharmacokinetics
a.	Speed of onset action
b.	Route of admin
Formulation
a.	Maximal available concentration
	E.g. don’t use drug same in cats as you would horses
b.	Irritancy
c.	Pain on injection
d.	Shelf life when open
e.	Combination with other drugs
Pharmacodynamics
a.	Quality of anaesthesia
b.	CV and resp effects
c.	Other effects (e.g. muscle relaxation)
d.	Quality og recovery
5.	Species and breed
6.	Personal preferences
7.	Anaesthesia environment and procedure
8.	Patient (disease, temperament)

Question 2

species considerations: dogs

Answer 2

o	Huge breed differences
	Dog de Bordeaux – large but brachy
o	Brachycephalics 
	Most challenging breed when it comes to induction and recovery
o	 Variable temperament 
	Docile, aggressive
o	iv access usually easy 
o	Can induce to effect

Question 3

Species considerations cat

Answer 3

o	Smaller than dogs
o	Behaviourally variable 
	Much less tolerant to restrain than dogs
	Spray larynx as prone to spasm
o	iv access can usually be achieved 
	not as easy as dog though!
o	 Mask sub clinical disease well 
o	 Can induce to effect

Question 4

Species considerations horsses

Answer 4

o	Huge breed differences
o	Large body mass 
o	iv access usually easy 
o	Do not like being recumbent
	Not natural
o	Cannot induce to effect

Question 5

Species considerations farm

Answer 5

o FPA’s, so legislation is important, and severely limits drug use
o iv access can be variably challenging
o Variable temperament

Question 6

Species considerationsexotics

Answer 6

o Many unhandled/ wild
o iv access very challenging
o Cannot induce to effect in many cases

Question 7

List maintenance agents

Answer 7

Inhalation agents:
isoflurane
sevoflurane
halothane

Injectable:
Propofol
alfaxalone
ketamine

Question 8

Which inhalation agents are licensed in SA and horses

Answer 8

Isoflurane 
	Licensed in SA
	Licensed in horses
Sevoflurane 
	Licensed in SA
	Not in horses but can use in horses as evidence provided safer recovery
(Halothane) 
	Historical drug, not commonly used thesedays

Question 9

Which injectables are licensed in SA and horses

Answer 9

o	Propofol
	Can function as either induction or maintenance agent
	Licensed in SA
	
o	Alfaxalone 
	Can function as either induction or maintenance agent
	Licensed in SA
	
o	 Ketamine
	Can function as either induction or maintenance agent
	Licensed in SA
	Licensed in LA

Question 10

How to assess depth of anaesthesia

Answer 10

• Eyeball position
• Pupil dilation
• Palpebral reflex
• Lacrimation in horses
• Horse eye position – cranial and ventral
• SA eye position – ventral medial
• Muscle relaxation

Question 11

ET tube

Answer 11

endotracheal tube
- Cuffed or non-cuffed ETT
- Cats can preserve laryngeal reflex after induction anaesthesia so uncuffed is suitable
o But if doing oral surgery cuffed better for cat as risk of aspirating blood
- Horses - cuffed
- Will depend on patient/ procedure
- Many different types
- Usually oro-tracheal intubation
- Maxillary fracture = unable to open mouth = prangeal intubation?

Question 12

What is a alternative to et tube

Answer 12

Supraglottic airway devices  LMA, V-Gel

• Sits over larynx rather than passing through it
• Has in inflatable rim to create a seal
• Useful in rabbits and some other cases

Question 13

Emergency cases

Answer 13

• Sometimes you need to be more creative
• Urinary catheters – providing time as so small
• Use stylets/ stomach tubes to “rail road” ETT
  o Life saving in certain situations
• Tracheostomy
  o Bypass URA (nasal and laryngeal)
• Plan B

Question 14

What are the most common injectable induction agents in dogs and cats?

Answer 14

propofol and alfaxalone

Question 15

What is teh most common induction agents in horses and farm

Answer 15

ketamine

Question 16

What are most maintenance of anaesthesia performed with?

Answer 16

inhalational agents