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Anaesthetics > Purpose of anaesthesia > Flashcards

Purpose of anaesthesia Flashcards

1
Q

What are ‘triad’ aims of anaesthetics

A
  • Unconsciousness
  • Muscle relaxation
  • The inhibition of pain
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2
Q

What is meant by analgesia in the unconscious patient?

A
  • conscious perception of pain is normally associated with the awake state

HOWEVER

  • noxious stimuli can still evoke physiological responses in the anaesthetized patient → drugs that decrease these responses are considered to be providing analgesia
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3
Q

Do volatile agents have analgesic properties?

A
  • contribute to analgesia while a patient is anaesthetised
  • do not provide any pain relief post-op

*large doses of volatile agents are needed to inhibit sympathetic response

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4
Q

How to quantify a potency of a volatile agent?

A

By Minimum Alveolar Concentration (MAC) value

MAC = concentration of the vapour in the lungs that is needed to prevent 50% of patients moving when subjected to a standard surgical incision

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5
Q

What do volatile agents do?

A
  • produce unconsciousness

in adequate doses:

  • partial muscle relaxants → by suppression of spinal reflexes
  • inhibition of movement to pain
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6
Q

What are the effects of IV anaesthetics? (2)

A
  • unconsciousness
  • amnesia
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7
Q

Do IV anaesthetics provide pain relief?

A

They are purely hypnotic agents → no analgesic properties

* with exception to Ketamine

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8
Q

Can IV anaesthetics inhibit movements in response to the surgery?

A

No, as they lack the ability to suppress spinal reflexes

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9
Q

Do benzodiazepines used in the theatre produce unconsciousness and amnesia, on their own?

A

Not on their own, in the doses used in the theatre

They are amnesic when combined with opiates and volatile/IV anaesthetics (synergistic effect)

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10
Q

Can benzodiazepines inhibit movements?

A

They contribute to muscle relaxation but do not completely inhibit movements (in standard doses)

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11
Q

Are benzodiazepines analgesics?

A

No

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12
Q

Mode of action of muscle relaxants

A

Muscle relaxants

(aka neuromuscular blockers)

MoA: they block transmission at the neuromuscular junction

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13
Q

Do muscle relaxants have anaesthetic or analgesic action?

A

No

*use of muscle relaxants without adequate anaesthesia → awareness while being paralysed

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14
Q

Can opioids produce unconsciousness and amnesia?

A

No

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15
Q

The aim of opioids use (in terms of surgery)

A

Analgesia during and after surgery

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16
Q

Can opioids produce a muscle relaxant effect?

A
  • do not produce muscle relaxation

BUT

  • they blunt perception of painful stimuli → inhibition of movements to pain during the surgery

*some opioids in very high doses may produce rigidity

17
Q

What does regional anaesthesia do?

A

Produces immobility, muscle relaxation and analgesia within a distribution of the block

18
Q

What’s multimodal analgesia?

A

Balanced analgesia requires the use of combinations of analgesic agents and techniques

This is also termed multimodal analgesia

19
Q

Advantages of balanced analgesia

A
  • reduce the amounts of each drug required while still being clinically effective
  • this may reduce some of the unwanted side-effects of the individual drugs
20
Q

Example of multimodial / balanced anaelgesia

A
21
Q

What are the responsibilities of anaesthetist?

A
  • providing balanced anaesthesia (during surgery)

Peri-operative period:

  • Reduction of the surgical stress response
  • Effective postoperative analgesia
  • Prevention of postoperative nausea and vomiting
  • Fluid homeostasis and management of bleeding
  • Temperature maintenance with prevention of hypothermia
  • Care of patient positioning and protection of pressure areas and eyes
22
Q

What are physiological responses for the painful stimuli and tissue injury during the peri-operative period?

A
  • Sympathetic nervous system mediated physiological changes
  • Neuro-humoral changes
  • Other hormonal and metabolic changes
23
Q

What do physiological responses to a painful stimuli/tissue injury (in a peri-operative period) may lead to?

A
  • Unwanted cardiovascular changes
  • Fluid retention
  • Electrolyte disturbances
  • Metabolic changes with a period of catabolism and hyperglycaemia
  • A systemic inflammatory response
  • Hypercoagulability
24
Q

The physiological responses in a patient to surgical insult cause raised or increased (8)

A
  • Adrenocorticotrophic hormone
  • Growth hormone
  • Vasopressin
  • Prolactin
  • Insulin resistance
  • Carbon dioxide (CO2) production
  • Oxygen consumption
  • Circulating catecholamine levels
25
Q

Aim of regional anaesthesia

A
  • prevents the transmission of nociceptive (painful) signals to the central nervous system, thus reducing the neuroendocrine stress response
  • this occurs for the duration of the block
26
Q

Does general anaesthesia stop physiological responses to pain/tissue injury (e.g. surgery)?

A
  • General anaesthesia does not abolish these responses completely
  • Patients still demonstrate a tachycardia under anaesthesia in response to stimulating procedures if inadequate analgesia has been given
27
Q

What physiological responses to pain can high-dose opioids block?

A

The opioid, e.g. remifentanil or large doses of fentanyl ⇒ prevents the hypertension and tachycardia and helps to maintain cardiovascular stability

28
Q

What do opioid drugs act on?

A

Receptors in CNS, both:

  • dorsal horn of the spinal cord
  • brain
29
Q

How does Paracetamol work?

A
  • act via inhibition of COX 3 ⇒ reduce prostaglandin synthesis
  • a weak anti-inflammatory
30
Q

How does Clonidine work?

A
  • alpha-adrenoreceptor agonist
  • analgesic, sedative and anti-hypertensive actions
31
Q

How does Ketamine work?

A
  • acts in the brain and spinal cord (central action)
  • local anaesthetic properties
  • used as adjunct to some regional blocks
32
Q

What does Tramadol act on?

A
  • opiate effects
  • also acts on descending inhibitory pathways → to reduce upward pain transmission
33
Q

What do intrathecal local anaesthetics do?

A

block conduction in spinal nerves

34
Q

How do local anaesthetics work?

A

Block sodium channels in a nerve cell membranes → signal conduction is reduced or prevented

35
Q

The pain ladder

A

Anaesthetics (9 decks)

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