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Pharmacology > Anaesthetics > Flashcards

Anaesthetics Flashcards

1
Q

What is anaesthesia

A

Loss of sensation

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2
Q

What are the effects of anaesthesia

A 
Sedation up to unconsciousness
Amnesia
Muscular relaxation
Spinal reflex suppression
Anxiolysis
Analgesia
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3
Q

Why does anaesthesia involve poly pharmacy

A

No single agent can produce all the effects of analgesia so require polypharmacy of short acting adjuvant Drugs

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4
Q

What are the types of anaesthesia

A

General: IV, Inhalational
Regional: spinal, epidural
Local
Dissociative

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5
Q

What is dissociative anaesthesia

A

Conscious sedation by inhibiting transmission between higher and lower brain centres

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6
Q

What are the steps in the procedure of anaesthesia

A 
Premedication: anxiolytic, anti emetic
Induction
Intra-operative analgesia
Muscle paralysis
Maintenance
Reversal of muscle paralysis
Post op analgesia
Anti-emetic
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7
Q

What are the anatomical targets for general anaesthesia and their effects

A 
CNS: 
Spinal cord - immobilisation 
Brainstem - Respiratory depression
Reticular formation - sedation
Hippocampus - amnesia
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8
Q

What are the molecular targets of GA

A

GABA receptors

NMDA Glutamate receptors

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9
Q

What is the mechanism of action of GA on GABA receptors

A

GABA receptor agonist
GABA receptors are LGICs on post synaptic membranes that cause Cl influx
Increase Cl influx and hyperpolarisation
Decrease neuronal excitability

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10
Q

What GA agents act on GABA receptors

A

Most except:
N2O
Ketamine
Xe

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11
Q

What is the mechanism of action of GA agents on NMDA glutamate receptors

A

NMDA glutamate receptor antagonist
NMDA receptors are LGICs in post synaptic membrane for Ca
Prevent Ca influx and depolarisation
Decrease neuronal excitability

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12
Q

How is consciousness controlled in GA

A

Balance between neuronal excitation and inhibition by balance between NMDA and GABA receptor activation

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13
Q

Give examples of inhalational GA

A 
N2O
Desflurane
Isoflurane
Sevoflurane 
Halothane 
Xenon (paediatric)
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14
Q

How is potency measured for volatile GA

A

Minimum alveolar concentration

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15
Q

What is MAC

A

% of inhaled anaesthetic in alveoli that abolishes response to surgical stimuli in 50% of patients

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16
Q

What is potency

A

Concentration of drug required to achieve 50% of its maximal response

17
Q

What is MAC of volatile GA dependent on

A

Lipid solubility: determines ability to dissolve into cell membranes and access target LGIC receptors

18
Q

What factors increase/decrease MAC

A

Age: infants (increase), elderly (decrease)
Hypothermia (decrease), Hyperthermia (increase)
Pregnancy (increase)
Opioids (decrease)
Other anaesthetics (decrease)
CNS stimulants (increase)
Alcoholism (increase)

19
Q

What effect does N2O have on MAC of other volatile agents

A

Decreases MAC

Thus acts as a MAC sparing agent, allows reduced dosing of agents when given together

20
Q

What is absorption of volatile agent from alveoli to CNS affected by

A

Alveolar concentration
Blood:gas coefficient
Distribution
Tissue:blood coefficient

21
Q

What does alveolar concentration of volatile agent indicate

A

It is proportional to CNS concentration of agent

22
Q

What is blood:gas coefficient

A

Degree of absorption of agent from alveoli into blood (solubility in blood)

23
Q

What is distribution dependent on

A

Relative blood supply of organs

24
Q

What is tissue:blood coefficient

Which tissue has highest coefficient

A

Degree of uptake of volatile agent from blood to tissues

Fat > muscle > CNS

25
Q

How is volatile GA eliminated

A

Withdrawal of anaesthesia after surgery
Decreased concentration of agent in blood
Agent moves out of cell into blood
Agent moves out of blood into alveoli
Agent breathed out unchanged
Eliminated from lungs with first order kinetics

26
Q

What is re-distribution of volatile GA agent

A

When proportion of volatile agent not removed from lungs and re-enters circulation and re-enters CNS

Pharmacology (19 decks)

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