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Aneasthesia > Induction > Flashcards

Induction Flashcards

0
Q

Which inhalational agents can be used to induce anaesthesia?

A
  • isoflurane
  • sevoflurane
  • halothane
  • desflurane (not licensed)
  • N20 (nitrous oxide)
  • xenon (new, expensive, specialised equipment needed)
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1
Q

Which injectable agents can be used to induce anaesthesia?

A
  • propofol
  • alfaxalone
  • ketamine
    > thiopentone/thiopental (old, can’t get vet form anymore)
    > etomidate (not licensed, human drug)
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2
Q

What is the most common route of induction?

A

IV

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3
Q

What do GA agents cause?

A

Dose dependant CNS depression

  • continuum from sedation -> anaesthesia
    eg. use of propofol as a sedative (michael jackson!)
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4
Q

How is CV and respiratory system affected by anaesthetic agents?

A 
> CV
- v CO
- vasodilation
- reduced BP 
- bad for kidneys etc. 
> resp
- v RR
- v TV (tidal volume)
= reduced minute volume
*dose-dependant*
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5
Q

Do GA drugs provide analgesia?

A

No - so must administer analgesics eg. opioids

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6
Q

What does uptake of GA depend on?

A
  • route of administration
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7
Q

What does distribution into tissues depend on?

A
  • blood flow (eg. injecting into sublumbar fat)
  • may be influenced by disease
  • lowers blood levels if injected into muscle etc.
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8
Q

Which species are particularly sensitive to a2 agonists?

A

Goats

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9
Q

What is metabolism of drugs influenced by?

A
  • Species
  • Disease state (esp. liver and kidneys, lungs for inhalation agents)
    > thiopental in a thin dog will maintain for a long time due to lack of body fat
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10
Q

How does propofol’s action differ in cats?

A

take a long time to recover
- enzyme lacking to conjugate glucuronides
- problems metabolising triglyceride lipid carrier of drug
> cumulative effects of the drug, can be TOXIC if given repeatedly
> Oxidative injury, Heinz body production, anaemia and death

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11
Q

Where does the induction agent ultimately act?

A

In the brain

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12
Q

How does age affect amount of induction agent required?

A
  • extremes of age require less
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13
Q

Should doses of GA drugs be learnt?

A

NO NOT FOR EXAMS!!! Know where to find them

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14
Q

WHat type of drug is propofol? What is it’s appearance and ROA?

A
  • a phenol
  • white opaque liquid (rich medium for bacterial growth)
  • must be given IV (not IM)
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15
Q

What can propofol be used for?

A

Induction AND maintainence eg. if cannot use inhalation agents (TIVA)

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16
Q

Pharmacodynamics of propofol

A
  • rapid onset after injection
  • blood levels v by redisribution
  • rapid metabolism (hepatic and extra-hepatic eg. lungs)
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17
Q

Effects of propofol

A
  • CV depression (vasodilation and v BP)
  • respiratory depression
    > so give SLOWLY over one minute
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18
Q

What is propclear?

A

Nanodroplet clear solution - no longer available

- caused extreme pain on injection

19
Q

What is propofol plus?

A

Preservative (benzyl alcohol) means can be used once opened (doesnt have to be discarded on the day)
> benzyl alcohol toxicity ->
- prolonged recovery and hyperkinesia in cats
- tremors in dogs
* DO NOT USE FOR TIVA*

20
Q

What type of drug is alfaxalone? What s it mixed with in preparations?

A

steroid - poorly soluable

- mixed with solubilising agent (cyclodextrin)

21
Q

ROA alfaxolone?

A

IV or IM

22
Q

How does alfaxolone differ to propofol?

A
  • rapid onset of action, short duration

- less CV and respiratory depression than propofol

23
Q

Potential side effects and cons of alfaxolone?

A

More expensive

Can see excitement on recovery if not adequately sedated

24
Q

What type of drug is ketamine?

A
  • Dissociative anaesthetic

- Analgesic actions at sub-anaesthetic doses (NMDA receptors)

25
Q

ROA ketamine

A

IM or IV

26
Q

What can ketamine be used for?

A

Inuction and maintainence of anaesthesia

27
Q

Why is ketamine NEVER GIVEN ALONE?

A

Excitation and muscle tension if given alone, always requires a sedative (benzodiazepine or a2 ag)
- also need to lubricate eyes as will remain open

28
Q

What situations is ketamine useful for?

A
  • angry cats

- brachycephalic breeds

29
Q

What is the triple combination? Which species is this commonly used in?

A 
- Aggressive cats
> Ketamine, medetomidine, opioid
- IM
- onset of action ~5 mins
- single injection alone suitable for short procedures
30
Q

Which species if ketamine commonly used in following sedation with a n a2 agonist?

A

Horses after PROFOUND sedation with an a2 ag

- given IV combination with a benzodiazepine (diazepam or midazolam)

31
Q

How does ketamine affect the CNS, CB and resp systems?

A

> CNS reflexes are preserved (palpebral, jaw tone, swallowing)
CV: SNS stimulated -> hypertension and tachycardia mildly, but some direct CV depression also
resp: mild resp depression

32
Q

Where is thiopental usually used nowadays?

A

Horses

  • not licensed for vet use anymore
  • used for induction (to effect) and as top up during maintainence
33
Q

Effects and potential side effects of thiopental?

A
  • irritant and necrosis if administered extravascualrly (alkaline)
  • CV and resp depression similar to propofol
34
Q

Can thiopental be used once vial is opened?

A

Yes for ~5d (pH so high nothing can grow)

35
Q

What drug or drug combination is best for high risk, sick patients? POtential problem with this drug?

A

*Etomidate
- minimal CV and resp depression
- problem: depresses adrenal gland function and cortisol production
> NOT LICENSED
* Fentanyl/midazolam combination
- very potent opioid

36
Q

Which inhalational agents are used for induction? Why would these be used over injectables?

A
  • sevoflurane or ioflurance delivered in oxygen

> aggressive patients if IV impossible

37
Q

What are the downsides to inhalational indcution?

A
  • ^ risk pollution and personnel exposure

- may see excitement/stress during induction

38
Q

Which inhalational agent is more irritating to respiratory passages and what effect may this have?

A

Isoflurane
-> breath holding
(but is cheaper)

39
Q

How can the smell of isoflurane be disguised to prevent mask avoidance?

A

Smear food inside mask

40
Q

What concentration roughly approximates brain concentration of anaesthetic drug?

A

ALveolar concentration

41
Q

What does partial pressure mean?

A

Amount in blood

42
Q

If an agent is very soluble in blood how is the partial pressure or tension of gas in the brain affected?

A

Lower in brain (doesnt ant to leave blood!)

43
Q

What is the partition coefficient?

A

Blood:Gas partition coefficient = no. particles gas in blood vs. alveolus

  • high number means gas is very soluble in blood (and therefore induction and recovery will take longer, as moving agent from blood to brain and back takes long time)
  • eg. halothane 2.4 [long induction and recovery], N2O and desflurane ~0.4 [short induction and recovery]
44
Q

Why is endotracheal intubation advocated?

A
  • o2 delivery
  • inhalational anaesthetic if required
  • protect airway from occlusion or aspiration
  • allow ventilation to be supported if depressed

Aneasthesia (11 decks)

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