Anaesthesia and Analgesia

Question 1

Why improve anaesthesia and analgesia?

Answer 1

• Decrease sources of variation in data
• Decrease no. of animals needed due to variation
• Decrease morbidity and mortality
• Impact welfare of animals
• Contribute to refinement and reduction
• Should refine entire perioperative period (acclimatisation -> post-operative)

Question 2

Why do we use anaesthetics?

Answer 2

• Prevent pain
• Prevent distress
• Provide immobility

Question 3

How do you prepare the animal for anaesthesia and surgery?

Answer 3

• Acclimatisation/conditioning
• Examine health status
• Pre-anaesthetic fasting (not rodents)
• Other preparations (shaving)

Question 4

When should be use pre-anaesthetic fasting?

Answer 4

• Dogs, cats, primates, ferrets, pigs (sometimes), sheep/ruminants (regurgitate)
• No need to fast in other species, may be harmful

Question 5

Which anaesthetics should we use?

Answer 5

• Consider all options, match to protocol and animal welfare
• Update protocols, including pre-, intra-, and post-operative care
• Availability of equipment and expertise
• Appropriate depth and duration of anaesthsia
• Interference w/ research aims
• Low mortality (<0.001%)

Question 6

Why use volatile liquid anaesthetics?

Answer 6

• Wide range
• Rapid loss of consciousness
• Non-irritant (X ether)
• Vary in pungency = affects willingness to breathe

Question 7

What considerations must be made when using isoflurane?

Answer 7

• Calibrated vaporizer
• Safe, popular, inexpensive
• Side effects: myocardial depression, hypotension
• Needs effective waste gas scavenging

Question 8

What considerations must be made when using sevoflurane?

Answer 8

• Similar to halothane and isoflurane = cardio and resp depression
• Relatively non-irritant
• More expensive
• Recovery free from involuntary excitement

Question 9

What are the chamber filling rates?

Answer 9

3 X Chamber time constant = 95%
3 X (chamber volume/flow rate) = 95%

Question 10

What injectables are being used in rodents?

Answer 10

• 26%: Ketamine/xylazine
• 19%: Pentobarbital (not recovery)
• 10%: Chloral hydrate (metabolic/resp/HR same)
• 3%: Tribromoethanol
• 3%: Thiopental
• 24%: Other

Question 11

What are the top choices of injectables in small rodents?

Answer 11

• Ketamine (w. medetomidine, xylazine, ACP, midazolam, diazepam)
• Hypnorm (w/ midazolam, diazepam)
• Propofol (IV)

Question 12

What are the top choices of injectables in birds?

Answer 12

• Ketamine (w/ medetomidine, xylazine, ACP, midazolam, diazepam)
• Propofol

Question 13

What do we do if IV admin isn’t an option?

Answer 13

• Use reversible anaesthetic E.g. ketamine/medetomidine, hypnorm/midazolam
• Use inhalational agent

Question 14

What do injectables have in common?

Answer 14

• Affect nervous system
• Depress resp function (hypercapnia, hypoxia, acidosis)
• Depress thermoregulation (hypothermia)
• Prolonged duration of action (IP/SC)
• Simple to admin
• Wide range = range of side effects
• Variable cost

Question 15

Why do you monitor animals under anaesthesia?

Answer 15

• Ensure anaesthesia is carried out safely and effectively
• Ensure anaesthesia is controlled and reproducible
• Identify and correct problems
• Remove outliers

Question 16

What do we monitor with anaesthesia?

Answer 16

• Depth of anaesthesia
• Respiratory function
• Cardio function
• Temperature
• Surgeon activity

Question 17

How do we monitor with anaesthesia?

Answer 17

• Clinical monitoring (limited, human error but useful)
• Electronic monitoring (specialist for small rodents)