Maintenance of Anaesthesia

Question 1

What are some potential problems when doing endotracheal intubation?

Answer 1

Occlusion of end of tube (prevented by Murphy’s eye sometimes), endobronchial intubation, compression of the tube or tracheal wall.

Question 2

What is it important to remember when intubating a cat?

Answer 2

Important to use a local anaesthetic to desensitise the larynx. It is also possible to use V-gels and laryngeal masks.

Question 3

What is TIVA?

Answer 3

Total intravenous anaesthesia

Question 4

In what two ways can TIVA be given?

Answer 4

Intermittent boluses or Continuous rate infusion (CRI)

Question 5

What are some advantages and disadvantages of giving TIVA in intermittent boluses?

Answer 5

Adv: Simpler and less equipment
Disadv: Swinging plane of anaesthesia based on perception, therefore sometimes v. deep and sometimes too light.

Question 6

In what two ways can constant rate infusions be measured and given?

Answer 6

Either give a target controlled infusion (maintain particular plasma level of drug) or a minimum infusion rate (aiming for conc. where 50% patients don’t respond).

Question 7

What is PIVA?

Answer 7

Partial intravenous anaesthesia - it is ‘balanced’ anaesthesia. Combination of injectable and inhalational anaesthesia.

Question 8

What is the MAC of an inhalational anaesthetic agent?

Answer 8

Minimum alveolar concentration = conc required to prevent movement in reponse to painful stimuli in 50% of animals.

Question 9

In clinical anaesthesia, what MAC do we aim for?

Answer 9

1.25-1.5 x MAC

Question 10

What is the MAC of Isoflurane in the dog, cat and horse?

Answer 10

Dog = 1.3
Cat = 1.6
Horse = 1.3

Question 11

What is the MAC of Sevoflurane in the dog, cat and horse?

Answer 11

Dog = 2.3
Cat = 2.6
Horse = 2.3

Question 12

What 3 factors DO NOT affect MAC?

Answer 12

Length of anaesthesia, gender, blood PH

Question 13

How do hypothermia, v. young/old animals, hypoxia, hypotension, CNS depressants, and pregnancy affect the MAC that should be given to an animal?

Answer 13

They decrease MAC

Question 14

How do hyperthermia, young and fit animals and excitation affect the MAC that should be given to an animal?

Answer 14

Increase MAC

Question 15

Why should Nitrous Oxide not be used as a sole anaesthetic agent?

Answer 15

MAC is ~200%. It is very insoluble and onset is rapid. Also a health risk from pollution (esp to pregnant women)

Question 16

When would you usually extubate an animal? What about if you’re concerned about the airway?

Answer 16

When swallowing reflex returns, later if worried about airway.