Anaesthetics Flashcards

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1
Q

Describe the hierarchy of anaesthesia types

A

Anaesthesia;

  • General: IV or Inhalation/ Volatile
  • Local: Can be used as Regional
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2
Q

What is conscious sedation

A

Use of small amounts of anaesthetic/ benzodiazepine to induce a ‘sleepy state’

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3
Q

IV anaesthetic agents can be used for ‘Induction’ or as the sole anaesthetic in TIVA (Total IV Anaesthesia)

List 4 IV Anaesthetic agents

A
  • Propofol (rapid)
  • Barbiturates (rapid)
  • Etomidate
  • Ketamine (slower)
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4
Q

Describe the 4 stages of Guedel’s Signs

A

Stage 1, Analagesia;

  • Conscious
  • Slight eye movement, normal muscle tone

Stage 2, Unconscious;

  • Erratic breathing
  • Excitement phase
  • Moderate eye movement
  • Normal to increased muscle tone

Stage 3, Surgical Anaesthesia;

  • Slight eye movement-> No eye movement
  • Slightly relaxed-> Markedly relaxed muscle tone

Stage 4, Respiratory Paralysis;

  • No eye movement
  • Flaccid muscle tone
  • No breathing-> Death
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5
Q

How is the potency of Volatile Anaesthetics described/ measured?

A

Minimum Alveolar Concentration, MAC;
- [Alveolar] at which 50% of subjects fail to move to surgical stimulus

  • At EQM, [Alveolar]=[Spinal cord]
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6
Q

List 8 things that affect the MAC

A
  • Age (Higher in infants)
  • Hyperthermia/ Hypothermia (higher/ lower)
  • Pregnancy (increased)
  • Alcoholism (increased)
  • Central stimulants (increased)
  • Other anaesthetics + sedatives (decreased)
  • Opioids (decreased)
  • Partition Coefficients
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7
Q

List and describe how 2 Partition Coefficients affect the MAC

A

Blood: Gas Partition;

  • Blood solubility
  • Low value/ solubility= Fast induction and recovery

Oil: Gas Partition;

  • Fat solubility
  • Determines Potency and rate of accumulation into fat
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8
Q

Suggest a chemical that is often added to volatile anaesthetic agents to lower the MAC

A

Nitrous Oxide, N2O

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9
Q

How do we describe potency of IV Anaesthetic agents?

A
  • [Plasma] needed to achieve a specific end point (e.g loss of eyelash reflex)
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10
Q

Describe the role of inhibitory GABAa receptors in Anaesthesia

(Main targets of anaesthetic agents)

A
  • GABAa receptors exist in membrane bilipid layer
  • Anaesthetic agent’s potency correlates with ability to bind to and activate GABAa receptor
  • GABAa receptor activation-> Cl- influx-> Hyperpolarisation of cells
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11
Q

All anaesthetics except for which THREE potential GABAa mediated Cl- conductance to depress CNS activity?

A
  • N2O
  • Xenon
  • Ketamine

(These probably inhibit excitatory NMDA receptors)

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12
Q

List 5 systems of the Brain/ CNS circuitry targeted by Anaesthesia

A
  • Reticular formation
  • Thalamus
  • Hippocampus (Memory affected)
  • Brainstem (Respiratory and CVS effects)
  • Spinal Cord (Dorsal horn and motor activity)
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13
Q

List 5 indications for Local Anaesthesia (thus Regional too)

A
  • Dentistry
  • Obstetrics
  • Regional surgery (patient awake)
  • Post-op (wound pain)
  • Chronic Pain management
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14
Q

List 3 Local Anaesthetics

A
  • Bupivacaine
  • Ropivacaine
  • Procaine
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15
Q

List 3 characteristics of Local Anaesthetics

A
  • High lipid solubility + potency
  • Dissociation constant, pKa gives some clue about time of onset (Low pKa= Faster onset)
  • Protein binding determines duration of action (Higher binding= Longer duration)
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16
Q

Describe the mechanism of action of a Local Anaesthetic

A
  • Uncharged form crosses membrane, then becomes charged
  • Charged form blocks Voltage-Gated Sodium Channel, so no Na+ Influx

(Block is use-dependent, meaning anaesthetic effect is greater when more APs are firing)

17
Q

How can you increase the duration of action of a Local Anaesthetic

A

Give Adrenaline

18
Q

Describe Regional Anaesthesia

A
  • Selectively anaesthetising part of the body
  • Patient remains awake
  • Uses Local Anaesthetic and/ or an Opioid

(Often described as a ‘Block’ of a nerve)

19
Q

List 4 ADRs of General Anaesthesia

Local/ Regional: Depends on agent, usually due to systemic spread

A
  • PONV (Especially with opioids)
  • CVS (Hypotension)
  • Post-op Cognitive Dysfunction (more common if older)
  • Chest infection

(Allergies/ Anaphylaxis?)