Clinical Induction of Anaesthesia Flashcards

1
Q

Induction of anaesthesia definition

A

the administration of a drug or combo of drugs at the beginning of an anaesthetic that results in the unconsciousness and allows you to intubate the patient

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2
Q

How fast does it take for induction of anaesthesia occur?

A

Thiopentone - 20-30 secs (1 circulation time)
All other drugs - about 2 mins (4 circulation times)

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3
Q

What are the methods of inducing anaesthesia?

A
  • IV injection given to effect
  • IM injection
  • Inhalation/mask or chamber
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4
Q

How long does IV injection of induction take?

A

up to 2 minutes

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5
Q

How long does IM injection of induction of anaesthesia take?

A

5-30 mins

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6
Q

Why is inhalation induction of anaesthesia not recommended?

A
  • stressful for P
  • poor for environment (world) & working environment
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7
Q

What are a few things to remember about induction?

A
  • IV & IM induction of anaesthesia is irreversible
  • Ensure you administer the correct dose (based on body weight)
  • Have a ‘Plan B’ in case of problems
  • Monitor the patient’s vitals
  • Be ready for intubation
  • have O2 source
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8
Q

What characteristics would make the ideal agent for induction of anaesthesia?

A
  • has rapid onset of action
  • minimum alteration to HR or BP
  • minimum post-induction apnoea
  • rapid & smooth recovery w/ no hangover
  • provides analgesia
  • provides good muscle relaxation
  • minimal organ toxicity
  • no venous/injection issues
  • suitable physical properties
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9
Q

Which drugs have a rapid onset of action (one ‘arm-to-brain’ circulation time - 30 seconds) for induction?

A

Thiopentone

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10
Q

Which induction drugs have minimum alterations to HR or BP?

A

Alfaxalone
Ketamine

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11
Q

Which induction agents have minimum post-induction apnoea?

A

Alfaxalone & ketamine
Propofol & Thiopentone especially

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12
Q

When propofol is given too much too fast during induction, what occurs?

A

signs of an overdose = post-induction apnoea

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13
Q

What induction drugs have a rapid & smooth recovery w/ no hangover?

A

Propofol

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14
Q

What induction agents provide analgesia?

A

Ketamine

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15
Q

What induction drugs provide good muscle relaxation?

A

Alfaxalone
Propofol
Thiopentone

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16
Q

What induction drugs cause minimal organ toxicity?

A

Alfaxalone
Propofol
Ketamine
Thiopentone

17
Q

What is a caution with using propofol in cats?

A

Repeated anaesthesia can cause Heinz Body anaemia

18
Q

What induction drugs cause no venous/injection issues?

A

Alfaxalone
Ketamine
Propofol - some preparations

19
Q

What induction drugs have suitable physical properties?

A

alfaxalone
Ketamine
Thiopentone

20
Q

What is marketed as the gold standard medication of induction of anaesthesia?

A

Propofol

21
Q

Why is propofol a popular induction agent (aka advantages)?

A
  • slow “to effect” induction w/o excitement
  • rapid recovery from anaesthesia
  • non-cumulative; suitable for TIVA
  • suitable for thin dogs & sighthounds
  • no perivascular damage
  • not arrhythmogenic
  • affordable
22
Q

What are the disadvantages of propofol?

A
  • CVS depression
  • Respiratory depression
  • hypercapnia if used for TIVA
  • pain on injection, short-lived
  • propofol ‘twitches’/myoclonus
  • shelf-life of preservative-free formulation very short (6-8 hrs)
  • Propofol 28 (w/ preservative) not suitable for repeated admin/infusion due to preservative
23
Q

What is a patient that the preservative form of propofol should not be used?

A

C-sections

24
Q

What type of drug is ketamine?

A

Dissociative anaesthetic which dissociates mind & body

25
Q

What signs of anaesthetic depth are used with ketamine?

A
  • active pharyngeal & laryngeal reflexes
  • open, central eye
  • nystagmus (equine)
  • increased muscle tone
  • hallucinations (humans)
26
Q

Ketamine advantage?

A

Analgesic

27
Q

Alfaxalone can be used for…

A
  • induction of anaesthesia
  • total intravenous anaesthesia (TIVA) as CRI
  • Sedation (IM)
28
Q

Alfaxalone is a … anaesthetic

A

steroid

29
Q

Injectable anaesthesia is made up by…

A

IM injections
repeated IV injections or top-ups
TIVA

30
Q

What drug combintions are used in small animal practice for injectable anaesthesia?

A
  • Medetomidine & ketamine +/- butorphanol IM
  • Ketamine & diazepam IV +/- top-ups
  • propofol IV, to effect
  • alfaxalone IV, to effect
31
Q

What drug combinations are used in equine practice for injectable anaesthesia?

A
  • A-2 agonist & ketamine +/- butorphanol IV
  • Triple Drip (GGE, Xylazine, Ketamine)
32
Q

What are the advantages of IM/IV anaesthetic techniques?

A
  1. useful for quick procedures
  2. useful for wild animals
  3. no expensive equipment required
  4. no operating room pollution
  5. can reverse some agents
33
Q

What are the disadvantages of using IM/IV anaesthetic techniques only?

A
  • no return of anaesthetic agents
  • easy to overdose
  • variable onset of action w/ IM inj
  • may be dfficult to control depth
  • resp depression common
  • may be difficult to prolong anaesthesia safely
  • IV injection may result in perivascular leakage
  • no ETT/airway protection
  • no anaesthetic machine or O2
  • inadeq monitoring of P
  • not suitable for high-risk P w/o fluids & O2
  • cannot resuscitate P if no airway protection/O2 support available
34
Q

What considerations should be taken into account before using IM/IV techniques of anaesthesia?

A
  • use combo of drugs if possible
  • use drugs w/ reversal agents
  • monitor P throughout procedure, incl post-op
  • provide analgesia, O2, fluid therapy
35
Q

TIVA is used to

A

reduce inhalant anaesthetics when possible

36
Q

TIVA can be

A

a single agent or combo of IV agents

37
Q

what drugs are used for dogs in TIVA admin?

A
  • Propofol & opioid (fentanyl, remifentanil) +/- NMB
  • Alfaxalone & opioid
38
Q

What drugs are used for horses in TIVA admin?

A
  • Ketamine, alpha-2, guaifenesin (‘triple drip’)