Drugs in Surgery Flashcards

1
Q

What are the ways to take general anaesthetics (GAs)?

A

Inhalational

Intravenous

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2
Q

What are premedications?

A

Muscarinic antagonist
Analgesic
Local anaesthetic
Muscle relaxant

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3
Q

What do GAs do?

A

Abolish awareness and response to pain

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4
Q

Why are GAs used in surgery?

A

Loss of consciousness, including memory
Suppression of pain
Suppression of skeletal muscle reflexes and tone

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5
Q

What are the toxic effect of GAs?

A

Depresses b.p. and resiration (low therapeutic index)

Liver/kidney damage (rarely)

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6
Q

What are the characteristics of the ideal anaesthetic?

A
Quick induction 
High potency
Reversibility
Good analgesia
Amnesia
No hangover
Low or harmless metabolism
Non-flammability 
Muscle relaxation 
Low toxicity
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7
Q

What is quick inductio?

A

Low solubility in blood, giving rapid saturation of bloos

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8
Q

What is high potency?

A

High lipid solubility

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9
Q

What is reversibility?

A

Gases give good control, injection less so

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10
Q

What is low toxicity?

A

Respiratory depression
Cardiovascular depression
Liver damage

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11
Q

What are volatile/ gaseous anaesthetics?

A

Many, simple, unreactive compounds

Halothane and nitrous oxide are commonly used

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12
Q

What is the compositiong of volatile/gaseous anaesthetics?

A

Numerous simple, small molecules

Mostly very unreactive compounds

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13
Q

What happens with intravenous agents after injection

A
Very rapid (high cerebral blood flow)
Very short duration (redistribution to other organs)
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14
Q

What is an example of an intravenous agent used?

A

Thiopentone (barbiturate)

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15
Q

What are the characteristics of thiopentone?

A

Low therapeutic index
Depresses heart and respiration
Repeat dose-> longer anaesthesia (slow metabolism)

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16
Q

What are intravenous agents?

A

Induction agents

Short procedures

17
Q

What are the mechanism of intravenous mechanisms?

A

Synaptic transmission, not axonal conduction

18
Q

Where is analgesia caused in intravenous mechanisms?

A

Reticular formation and thalamus

19
Q

Where is unconsciousness caused in intravenous mechanisms?

A

Rf and hippocampus

20
Q

Where is amnesia caused in intravenous mechanisms?

A

hippocampus

21
Q

What mechanism was recognised by is now discredited?

A

Non-receptor

22
Q

What is the lipid-solubility mechanism?

A
Interact with hydrophobic structure
Membranes- volume expansion (pressure reversal)
Protein binding (hydrophobic sites)
23
Q

What do receptors encourage?

A

Opening of chloride channels (e.g. GABA receptors)

24
Q

What does Cl- entry into a neurone cause?

A

Hyperpolarisation and inhibition

25
Q

What do general anaesthetics do in terms of the Cl- entering the neurone?

A

Enhance the response

26
Q

What drugs are used as a premedication?

A

Hyoscine
Morphine
Lignocaine

27
Q

What is hyoscine?

A

Muscarinic receptor antagonist- dries up secretions of saliva and bronchial mucus

28
Q

What is morphine?

A

Opiate analgesic

Prevents post-operative pain

29
Q

What lignocaine?

A

Local anaesthetic- blocks conduction in sensory nerves

30
Q

What do muscle relaxant drugs do?

A

Voluntary muscles can be relaxed by drugs which interfere with nicotinic receptors

31
Q

What are some examples of muscle relaxant drugs?

A

Tubocurarine

Suxamethonium

32
Q

What does tubocurarine do?

A

Non-depolarising
Competes with ACh
Long acting
Reversible with ChE inhibitor

33
Q

What does suxamethonium do?

A

Depolarising
Cation channels stay open
Short acting
Not reversible with ChE inhibitor