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Flashcards in Maintenance of anaesthesia Deck (36)
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1

When can you intubate?

Sufficient depth of anaesthesia (eyes rotate ventrally, minimal/sluggish palpebral reflex, loose jaw tone, no swallowing reflex on stimulation) --> Pull tongue out --> laryngoscope on tongue (don't touch epiglottis or larynx) --> visualise laryngeal opening --> LA and lubricaton

2

How do you measure an ETT?

measure to point of shoulder

3

What are problems with ETTs? 5

- Occlusions at end - prevented by murphy's eye
- Endobronchial intubation
- Mucus in tube (occulsion and infection)
- Compression of inside of tube
- Stretching of tracheal wall

4

Special considerations - cats and ETTs

spray larynx with local anaesthetic (desensitises and reduces laryngospasm). Use intubeaze (lidocaine spray)

5

List 2 alternatives to ETT in cats

V-gel
Laryngeal mask

6

T/F- mist anaesthetics don't provide analgesia

True (one exception = ketamine). (Analgesia is still required even though patient is unconscious to prevent upregulation of pain processing pathways_.

7

How can anaesthesia be maintained? 4

Inhalational
Intravenous
Combination (injectional and inhalational)
Single IM injection (occasionally)

8

Define PIVA

Partial IntraVenous Anaesthesia

9

List 4 injectable maintenance anaesthetics

Best for TIVA:
Propofol
Alfaxalone

Accumulate so not good for CRI, use for intermittent:
Ketamine
Thiopental

10

List 6 inhalational maintenance anaesthetics

Isoflurane
Sevoflurane
Halothane
Desflurane
NO2
Xenon

11

Outline intravenous maintenance

TIVA = total intravenous anaesthesia
Intermittent boluses or continuous rate infusion (CRI)

12

Advantages of intermittent bolus/CRI for maintaining anaesthesia

INTERMITTENT: simpler, less equipment, swinging plane of anaesthesia
CRI: target controlled infusion (TCI) possible, minimum infusion rate (MIR)

13

How are inhalational agents metabolised?

Administered and removed from body via lungs (except halothane - liver.
Redistributed to brain and other tissues

14

How does fat solubility affect inhalational agents?

Fat solubility may slow recovery from a long anaesthetic (think vessel rich vs. vessel poor tissues)

15

What factors affect inhalational agent uptake? 2

- Pressure gradient from vaporiser to brain
- Brain concentration approximates alveolar concentration

16

What factors affect speed of induction?

- High pp in lungs = high pp in brain
BUT agents that are very soluble in blood will have lower pp in lungs --> lower pp in brain therefore speed of induction/recovery for soluble agents is slower.

17

What is the blood/gas partition coefficient?

Number of parts of gas in blood versus alveolus
High number = gas very soluble in blood = slower induction and slower to change depth of anaesthesia during maintenance

18

Define MAC

Minimum Alveolar Concentration that is required to prevent movement in response to painful stimulus in 50% animals. For clinical anaesthesia aim for 1.25-1.5 times MAC. Depends on other sedatives/anaesthetics (may cause a MAC sparing effect). MAC values vary between species.

19

List factors that influence MAC and how.

Hypothermia (decrease), hyperthermia (increase)
Age - young/old (decrease), young/fit (increase)
Severe hypoxia/hypercapnia (decrease)
Severe hypotension (decrease)
CNS depressant drugs (decrease)
Excitation (increase)
Pregnancy (decrease)

20

Name 3 factors that don't influence MAC

length of anaesthesia
gender
normal blood pH

21

What is the range for normal blood pH?

7.35-7.45

22

What is the MAC value in dogs for isoflurane and sevoflurane?

ISOFLURANE = 1.3
SEVOFLURANE = 2.3

23

What is the MAC value in cats for isoflurane and sevoflurane?

ISOFLURANE = 1.6
SEVOFLURANE = 2.6

24

What is the MAC value in horses for isoflurane and sevoflurane?

ISOFLURANE = 1.3
SEVOFLURANE = 2.3

25

Is sevoflurane licensed in dogs, cats and horses?

Yes - dogs
No - cats and horses

26

Which anaesthetic reduces CO the most?

Halothane - mainly
Also some reduction with iso and sevo

27

T/F: respiratory depression is similar for all anaesthetics

True

28

How much metabolism is performed by the liver for differentinhalational anaesthetics?

Isolfurane - 0.2%
Sevoflurane - 2%
(Halothane - 20% - the exception)
Desflurane - 0.02%

Predominantly the lung

29

How is sevoflurane metabolised?

- Theoretically free fluoride ions are released (nephrotoxic but no clinically reported problems)
- Compound A formed during reaction with hot and dry CO2 absorber (nephrotoxic, newer absorbers prevent this)
- Low flow anaesthesia potentiate these processes

30

T/F: sevoflurane is the best anaesthetic choice for renal disease

False (nephrotoxtic free radicals and compound A produced). Isoflurane is a much better option.

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