2- Maintenance of anaesthesia

Question 1

There are 3 ways that anaesthesia can be maintained:

Answer 1

Inhalation anaesthesia
Total intravenous anaesthesia
Partial intravenous anaesthesia- which is a mixture of the 2

Question 2

What agent is anaesthesia maintained by?

Answer 2

Volatile agents - iso/sevo

Question 3

What is the volatile anaesthetic agent combined with in the vaporiser?

Answer 3

Fresh gas

Question 4

What does the rate of the anaesthetic in the plasma depend on?

Answer 4

Conc of the agent, ventilation, cardiac output & solubility of the agent in the blood

Question 5

Define MAC (minimum alveolar concentration)

Answer 5

Concentration of vapour in the alveoli of the lungs that is needed to prevent 50% of patients moving in response to surgical stimulus

Question 6

Name 2 factors that affect MAC

Answer 6

Drug given in pre-med - often decreases MAC

Body temperature

Age

Individual variation

Question 7

What animal’s is isoflurane licensed in?

Answer 7

Dogs, cats and horses

Question 8

What affects good and bad do volatile agents have on the patient?

Answer 8

Anaesthesia & dose-dependent analgesia

Profound cardiovascular & Respiratory depression (dose-dependant)

Question 9

Cardiovascular depression is mediated via…

Answer 9

myocardial depression

Question 10

What maintenance agent has an extremely high MAC thus is not usually used a sole anaesthetic agent?

Answer 10

Nitrous oxide

Question 11

Define Total IV Anaesthesia (TIVA)

Answer 11

When anaesthesia is both induced & maintained by intravenous administration of drugs

Question 12

In small animals what 2 drugs are licensed are licensed for TIVA use?

Answer 12

Alfaxalone & Propofol

Question 13

T/F Alfaxalone & Propofol provide analgesia

Answer 13

FALSE

Question 14

What is in the ‘triple drip’ used in horses?

Answer 14

Guaifenesin (muscle relaxant)
Ketamine (NMDA receptor antagonist)
Detomidine (alpha 2 agonist)

Question 15

Define partial IV Anaesthesia (PIVA)

Answer 15

Combination of intravenous & inhalation aesthetic techniques

Question 16

What is the aim of PIVA?

Answer 16

Reduce the amount of inhalation anaesthetics due to there cardiovascular and respiratory depression effects.

The idea is you can use less and thus have fewer negative effects = balanced anaesthesia

Question 17

What effects do opioids have on MAC?

Answer 17

Mac sparing - moderate doses can result in a big reduction

Question 18

What happens when you turn on the fresh gas flow but not the vaporiser on the anaesthetic machine

Answer 18

the gas flows along the bypass pathway to the patient, will not contain any volatile agent

Question 19

What happens to the gas when you turn on the vaporiser on an anaesthetic machine

Answer 19

Fresh gas flow divided–> half goes into anaesthetic chamber and become saturated –> flows out mixes with the fresh of the gas and goes to patient

Question 20

How is inhalation anaesthetics removed

Answer 20

by a anaesthetic scavenger- there are different types

Question 21

Which species is sevoflurane licensed in

Answer 21

Dogs and cats

Question 22

Which volatile agent has a slightly higher MAC and a lower blood gas solubility

Answer 22

Sevoflurane- means it diffuses into tissues and therefore the brain more quickly than iso- quicker change in anaesthetic depth

Question 23

T/F isoflurane is more expensive than sevoflurane

Answer 23

False

Question 24

Which inhalation agent is best to use for mask induction

Answer 24

Sevoflurane- n as it doesn’t smell/ taste pungent and is is quicker to effect.

Question 25

T/F Nitric oxide has health and safety and environmental concerns

Answer 25

True- main reason it isn’t used - the impact of nitrous oxide is significantly greater than for isoflurane or sevoflurane

Question 26

What rules are inhalation agents restricted by

Answer 26

COSHH- (Control of substances hazardous to health)
Because they are volatile and not metabolised by the patient there is potential for personnel exposure

Question 27

List 2 situations when the use of TIA be appropriate

Answer 27

intrathoracic surgery or neuro disease in small animals
field anaesthesia in horses - when can’t give inhalation agents