15. Anaesthetics Flashcards

1
Q

What are the two broad categories of anaesthesia?

A

General and local.

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2
Q

Outline the process of anaesthesia throughout surgery.

A

Premedication (feel calm), induction (knocked out), intraoperative analgesia (pain relief), muscle paralysis (intubation), maintenance (keep asleep), reverse muscle paralysis (restore respiratory function), provision for post operative nausea and vomiting.

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3
Q

What are some IV gas volatile general anaesthetics?

A

Propogol, barbiturates, etomidate, ketamine.

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4
Q

What are the four stages of Guedel’s signs?

A

1 - analgesia + consciousness; 2 - unconscious, erratic breathing; 3 - surgical anaesthesia with increasing depth until weak breathing; 4 - respiratory paralysis and death.

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5
Q

What is anaesthesia a combination of?

A

Analgesia, hypnosis, depression of spinal reflexes, muscle relaxation.

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6
Q

What is potency?

A

Dose/concentration for a drug to have an effect.

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7
Q

What does MAC stand for?

A

Minimum alveolar concentration - volatile anaesthetic potency.

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8
Q

What is the value of MAC?

A

[Alveolar] at 1atm at which 50% of subjects fail to move to surgical stimulus.

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9
Q

What is the anatomical substrate for MAC and why?

A

Spinal cord as concentration is the same as in alveolar at equilibrium.

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10
Q

What is the neural substrate for loss of consciousness?

A

Brain.

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11
Q

What factors affect induction and recovery in anaesthetics?

A

Partition coefficients (solubility). Blood:gas partition in blood, oil:gas partition in fat.

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12
Q

What does a low blood:gas partition mean for induction and recovery in anaesthetics?

A

Low value means fast induction and recovery.

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13
Q

What affects MAC?

A

Age (high in infants, low in elderly), hyperthermia (increases), hypothermia (decreases), pregnancy (increased), alcoholism (increased), other anaesthetics (decreased), opioids (decreased.

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14
Q

Why is nitrous oxide often added to other volatile agents in anaesthetics?

A

It reduces the dosing required.

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15
Q

What is a key receptor target in anaesthetics?

A

GABAa receptors.

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16
Q

What is the effect of anaesthetics in GABA activity?

A

Potentiates it - anxiolysis, sedation, anaesthesia. Increase Cl- conductance and depresses CNS activity.

17
Q

What is the molecular-cellular target in anaesthetics?

A

Brain consciousness (balance between glutamate excitation and GABA inhibition).

18
Q

What are the effects of anaesthetics on the brain circuitry?

A

Reticular formation depressed, hippocampus depressed, brainstem depressed, spinal cord dorsal horn and motor neuronal activity depressed.

19
Q

What are the main IV anaesthetics?

A

Propofol, barbiturates, ketamine.

20
Q

What is TIVA?

A

Total intravenous anaesthesia - only IV anaesthetics used.

21
Q

What are the mechanisms of action of IV anaesthetics?

A

Most potentiate GABAa, ketamine works on NMDA.

22
Q

What is IV anaesthetic potency?

A

Plasma concentration needed to achieve a specific end point.

23
Q

When are local and regional anaesthetics used?

A

In dentistry, obstretrics, regional surgery, post-op, chronic pain management.

24
Q

What are some main local anaesthetics?

A

Lidocaine, bupivacaine, ropivacaine, procaine.

25
Q

What is the mechanism of action of bupivacaine infiltration for wound analgesia?

A

Blocks Na+ channel so no action potential.

26
Q

What is the role of regional anaesthetics?

A

Selective anaesthetising of a part of the body, a ‘nerve block’.

27
Q

What are the main general anaesthetic ADRs?

A

PONV (post-op nausea + vomiting), CVS hypotension, POCD (post-op cognitive dysfunction,worse with age), chest infection.

28
Q

What is the main regional anaesthetics ADR concern?

A

Na+ channel blocker so risk of cardiovascular toxicity.