Drugs in Surgery

Question 1

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

Answer 1

Inhalational

Intravenous

Question 2

What are premedications?

Answer 2

Muscarinic antagonist
Analgesic
Local anaesthetic
Muscle relaxant

Question 3

What do GAs do?

Answer 3

Abolish awareness and response to pain

Question 4

Why are GAs used in surgery?

Answer 4

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

Question 5

What are the toxic effect of GAs?

Answer 5

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

Liver/kidney damage (rarely)

Question 6

What are the characteristics of the ideal anaesthetic?

Answer 6

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

Question 7

What is quick inductio?

Answer 7

Low solubility in blood, giving rapid saturation of bloos

Question 8

What is high potency?

Answer 8

High lipid solubility

Question 9

What is reversibility?

Answer 9

Gases give good control, injection less so

Question 10

What is low toxicity?

Answer 10

Respiratory depression
Cardiovascular depression
Liver damage

Question 11

What are volatile/ gaseous anaesthetics?

Answer 11

Many, simple, unreactive compounds

Halothane and nitrous oxide are commonly used

Question 12

What is the compositiong of volatile/gaseous anaesthetics?

Answer 12

Numerous simple, small molecules

Mostly very unreactive compounds

Question 13

What happens with intravenous agents after injection

Answer 13

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

Question 14

What is an example of an intravenous agent used?

Answer 14

Thiopentone (barbiturate)

Question 15

What are the characteristics of thiopentone?

Answer 15

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

Question 16

What are intravenous agents?

Answer 16

Induction agents

Short procedures

Question 17

What are the mechanism of intravenous mechanisms?

Answer 17

Synaptic transmission, not axonal conduction

Question 18

Where is analgesia caused in intravenous mechanisms?

Answer 18

Reticular formation and thalamus

Question 19

Where is unconsciousness caused in intravenous mechanisms?

Answer 19

Rf and hippocampus

Question 20

Where is amnesia caused in intravenous mechanisms?

Answer 20

hippocampus

Question 21

What mechanism was recognised by is now discredited?

Answer 21

Non-receptor

Question 22

What is the lipid-solubility mechanism?

Answer 22

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

Question 23

What do receptors encourage?

Answer 23

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

Question 24

What does Cl- entry into a neurone cause?

Answer 24

Hyperpolarisation and inhibition

Question 25

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

Answer 25

Enhance the response

Question 26

What drugs are used as a premedication?

Answer 26

Hyoscine Morphine Lignocaine

Question 27

What is hyoscine?

Answer 27

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

Question 28

What is morphine?

Answer 28

Opiate analgesic | Prevents post-operative pain

Question 29

What lignocaine?

Answer 29

Local anaesthetic- blocks conduction in sensory nerves

Question 30

What do muscle relaxant drugs do?

Answer 30

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

Question 31

What are some examples of muscle relaxant drugs?

Answer 31

Tubocurarine | Suxamethonium

Question 32

What does tubocurarine do?

Answer 32

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

Question 33

What does suxamethonium do?

Answer 33

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