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Yr 2 - Control > General Anaesthesia > Flashcards

General Anaesthesia Flashcards

1
Q

Requirements for general anaesthetics?

A
  • Intravenous access: to give anaesthetic agents
  • Start process
    • Induction of anaesthesia with induction agents
    • Analgesia and muscle relaxation – and anti-sickness drugs
  • Maintain process
    • Agents for amnesia, analgesia, muscle relaxation
    • Replace fluid/blood loss
  • Reverse process
    • Reverse muscle relation
    • Maintain post-operative analgesia
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2
Q

The first step in GA is amnesia induction. How quickly do amnesia induction agents induce loss of consciousness?

A

Induce loss of consciousness in one-two arm-brain circulation times (10-20 seconds).

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3
Q

What is an ‘arm-brain circulation time’?

A

the time it takes for the drug to travel from the injection site to the brain

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4
Q

Describe the properties of IV agents used for GA

A
  • Quick onset
  • Short duration (redistribution to fat and muscle)
  • Commonly used as a bolus for induction, but increasingly as an infusion for maintenance
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5
Q

You must be aware of potency in IV agents in GA. What is Cp50?

A

The concentration of the agent in the blood that will prevent movement after a skin incision in 50% of the patients to whom the agent is given.

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6
Q

Mechanism of action for GAs?

A
  • GA’s stimulate inhibitory receptors (such as GABA receptor) and inhibit excitatory receptors
    • Produces overall inhibition
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7
Q

Ideal properties of IV induction agents:

A
  • Simple preparation
  • Compatible with other agents
  • Painless on administration
  • High potency and efficacy
  • Predictable action within one circulation time
  • Minimal cardiovascular effects or other toxicity
  • Depression of airway reflexes for intubation
  • Rapid and predictable offset of effect
  • Rapid metabolism for minimal hangover
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8
Q

What are the 4 standard drugs used in IV induction?

A
  1. Propofol
  2. Thiopentone
  3. Ketamine
  4. Etomidate
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9
Q

what is the most common drug for IV induction?

A

Propofol

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10
Q

What are the advs/disadvs of propofol?

A

Advs:

  • Excellent suppression of airway reflexes; patient falls asleep and stop breathing –> need to put in an airway!
  • Decreases incidence of PONV (postoperative nausea and vomiting)

Disadvs:

  • Marked drop in HR+BP
  • Pain on injection (as lipid based)
  • Involuntary movements
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11
Q

what are the advs/disadvs of Thiopentone?

A

Advs:

  • Faster than propofol, used for rapid sequence induction
  • Antiepileptic properties and protects brain

Disadvs:

  • Drops BP, rise in HR
  • Rash/bronchospasm
  • Accidental intra-arterial infection: thrombosis and gangrene
  • Contraindicated in porphyria
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12
Q

How does ketamine differ from the other drugs for IV induction?

A
  • Anterograde amnesia and profound analgesia (different to others)
  • Sole anaesthesia for short procedures
  • Slow onset (90 seconds)
  • Only used in a small number of cases
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13
Q

Disadvs of ketamine?

A
  • Nausea, vomiting
  • Emergence phenomenon (depressed or hyperexcitable, vivid dreams)
    • Anxiety or distress on awakening from ketamine sedation, which settles spontaneously
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14
Q

What are the advs/disadvs of Etomidate?

A

Advs;

  • Rapid onset (0.3mg/kg)
  • Haemodynamic stability, lowest incidence of hypersensitivity reaction

Disadvs;

  • Pain on injection
  • spontaeneous movements
  • adreno-cortical suppression
  • highest incidence PONV (Postoperative nausea and vomiting)
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15
Q

How long do induction agents last?

A

Induction agents all only last 4-10 mins BUT want patient to be asleep for duration of operation

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16
Q

What are the 2 ways in which anaesthesia can be maintained after induction?

A
  1. Propofol infusion
  2. Inhalational agents
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17
Q

How is anaesthesia maintained using propofol infusion?

A
  • Continuing infusion of induction agents; propofol infusion (total intravenous anaesthesia)
  • TIVA is a technique of GA which uses a combination of agents given exclusively by the IV route without the use of inhalation agents
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18
Q

What is inhalational anaesthesia?

A

Can also give the patient volatile gases which are absorbed into the blood and keep the patient asleep for the duration of the operation

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19
Q

What are the 2 routes of administration of inhalational anaesthesia?

A
  1. Vaporisers
  2. Breathing circuits
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20
Q

What are the requirements for inhalational anaesthetics?

A
  • Non-flammable
  • Stable with material (plastics, metal), long shelf life
  • Environmentally friendly
  • Cheap and easy to manufacture
  • Pleasant to inhale, non-irritant
  • Fast onset
  • High potency
  • Minimal effects to other systems
  • No biotransformation
  • Non-toxic to theatre personnel
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21
Q

Which receptor does propofol and etomidate target?

A

GABAA receptors

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22
Q

When are inhalational agents started?

A

Immediately after induction

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23
Q

What are the 3 inhalational agents used for amnesia?

A
  1. Isoflurane
  2. Sevoflurane
    3.
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24
Q

How des the solubility of the inhalational agent affect the onset and recovery?

A
  • Low solubility = fast equilibration
  • Agents with low solubility= fast onset and quick recovery
  • Highly fat-soluble agents: GA given for a long time accumulates in fat, which can result in a hangover effect for hours
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25
Q

Inhalational agents are most commonly used for maintenance, but can be used for induction. When would this be the case?

A

if no IV access can be established

26
Q

What are the 3 neurological effects of anaesthetics?

A

1.

27
Q

Anaesthetics and the receptors they target

A
28
Q

Which inhalational agent would be used if no IV access can be established?

A

Sevoflurane

29
Q

Desflurane has a low lipid solubility. What does this mean?

A
  • Rapid onset and offset
30
Q

Which inhalational agent is used for organ transplant? Why?

A

Isoflurane –> has the least effect on organ blood flow

31
Q

Which inhalational agent is sweet smelling?

A

Sevoflurane

32
Q

What are the potential adverse effects of inhalational agents?

A
  • Vasodilation
  • Decrease cardiac contractibility
  • Potentially affect organ perfusion
  • Malignant hyperthermia
  • Hepatotoxicity (Halothane, mostly withdrawn)
33
Q

What would be the best inhalational agent for a long, 8-hour finger re-implantation?

A

Desflurane –> low lipid solubility therefore rapid onset and offset

34
Q

What is the preferred inhalational agent for a chubby child with no IV access?

A

Sevoflurane –> sweet smelling

35
Q
A
36
Q

What is minimum alveolar concentration (MAC)?

A

The minimum alveolar concentration (MAC) is the minimum concentration of an inhaled anesthetic at 1 atm of pressure that prevents skeletal muscle movement in response to a surgical incision in 50% of patients. (stimulus is a set depth and width of skin incision)

37
Q

What is one MAC of:

a) nitrous oxide
b) sevoflurane
c) isoflurane
d) desflurane

A

a) 104%
b) 2%
c) 1.15%
d) 6%

38
Q

if 2% MAC for Sevoflurane is achieved, what does this mean?

A

if 2% MAC for Sevoflurane is achieved, 100% of patients are asleep but 50% of patients will not react to a surgical stimulus

39
Q

What is the 2nd step in GA?

A

Analgesia

40
Q

What are analgesic drugs in GA required for?

A
  • Insertion of airway
  • Laryngeal mask airway
  • Intubation
  • Intraoperative pain relief
  • Postoperative pain relief
41
Q

Examples of analgesic drugs used in GA:

A
  • Short acting: Remifentanil > Alfentanil > Fentayl
  • Long acting: Intra-op and post-op analgesia e.g. Morphine and Oxycodone
  • Weaker: Tramadol, Dihydrocodeine
  • Post op: Paracetamol (most common) and NSAIDS (if not contraindicated)
42
Q

What is the 3rd step in GA?

A

Muscle relaxation

43
Q

What is muscle relaxation required for in GA?

A
44
Q

What are the 2 types of muscle relaxants used in GA?

A
  1. Depolarising
  2. Non-depolarising
45
Q

What is the depolarising muscle relaxant?

A

Suxamethonium

46
Q

Examples of non-depolarising muscle relaxants:

A
  • Short acting: Atracurium, mivacurium
  • Intermediate acting: Vecuronium, rocuronium
  • Long acting: Pancuronium
47
Q

How are muscle relaxants reversed at the end of surgery?

A

Reversal at end of procedure to allow breathing: Neostigmine and Glycopyrrolate

48
Q

How can a patient’s consciousness be monitored during surgery?

A
  • Clinical signs
  • Measure level MAC
  • BIS monitor
  • Isolated forearm
  • Evoked potentials
49
Q

Which of the following ion-channels are not affected by general anaesthetic agents:

  1. GABA channels
  2. Na K ATPase
  3. 5HT3 channels
  4. NMDA receptors
A

Na K ATPase; General anaesthetics block GABA dependent chloride, Glycine sensitive, 5 HT3 sensitive and Acetylcholine sensitive and Glutamate sensitive channels.

50
Q

What is the best induction agent for a patient requiring a burn dressing change?

  • Propofol
  • Thiopentone
  • Etomidate
  • Ketamine
A

Ketamine; Ketamine causes dissociative anaesthesia and profound analgesia and can be useful to perform small procedures on ward in low doses.

51
Q

What is the best induction agent for a patient with a history of heart failure requires a general anaesthetic?

  • Propofol
  • Thiopentone
  • Etomidate
  • Ketamine
A

Etomidate; Etomidate causes least haemodynamic changes of all four commonly used induction agents.

52
Q

Best Induction agent for a patient undergoing arm operation under GA with an laryngeal mask airway (LMA)?

  1. Propofol
  2. Thiopentone
  3. Etomidate
  4. Ketamine
A

Propofol; Propofol the most common induction agent used for general anaesthesia as it cases suppression of airway reflexes.

53
Q

MAC for an inhalational agent stands for…?

A

Minimum alveolar concentration

54
Q

What is the MAC of Sevoflurane?

A

2%

55
Q

Best inhalational agent for induction is a chubby child who has no intravenous access ?

  1. Desflurane
  2. Isoflurane
  3. Sevoflurane
  4. Nitrous oxide
A

Sevoflurane; Sevoflurane is sweet smelling and is used for inhalational induction.

56
Q

Most commonly used non-opiod analgesic agent in anaesthesia?

A

Paracetamol; due to its safety profile is the most common oral/iv analgesic used for pain.

57
Q

Which of the following is a depolarising muscle relaxant?

  1. Suxamethonium
  2. Mivacurium
  3. Vecuronium
  4. Atracurium
A

Suxamethonium

58
Q

Which of the following is used for reversal agent for muscle relaxation?

  1. Neostigmine and glycopyrrolate
  2. Phenylephrine
  3. Metaraminol
  4. Rocuronium
A

Neostigime and glycopyrrolate

59
Q

Which of the following is not used to assess awareness under anaesthesia?

  1. Clinical signs
  2. MAC
  3. BIS
  4. EMG (Electromyography)
A

EMG

60
Q

What does BIS stand for?

  1. Bilateral index of Sleep
  2. Bilateral index of Somnolence
  3. Bispectral Index
  4. Biomedical Index of Sleep
A

Bispectral index

Yr 2 - Control (71 decks)

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