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SPC- Anaesthetics > Pharmacology of Anaesthesia > Flashcards

Pharmacology of Anaesthesia Flashcards

1
Q

What is the most commonly used induction agent?

A

Propofol which is delivered via an IV canulla

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2
Q

What is the aim of induction agents?

A

To cause a rapid loss of consciousness and this is then followed with maintainance analgesia

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3
Q

Why are elederly patients more prone to overdose during IV induction?

A

Due to a poor cardiac output they are more likely to have higher doses of IV induction agents given to them as it takes longer for the induction agent to reach the brain and cause analgesia

This is called the arm brain circulation time

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4
Q

What are some advantages to induction analgesia?

A

Pleasant for patient
Can cause a rapid loss of consciousness
Relatively predictable

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5
Q

What are some disadvantages to induction agents?

A

Overdoses in people with poor cardiac output and elderly due to increased arm brain circulation time
Adverse respiratory and cardiovascular effects

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6
Q

What causes rapid falls in plasma concentration of the induction agent?

A

This is due to redistribution of the drug into the muscle, specifically the fat of muscle.

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7
Q

What causes gradual falls in the plasma concentration of a drug?

A

This is due to metabolic clearance by the liver and kidneys

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8
Q

What does propofol look like?

A

It is a cloudy white liquid

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9
Q

What is the most common IV induction agent?

A

Propofol

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10
Q

Why might etomidate be used as an induction agent?

A

It is pretty CV stable and so maybe used in cardiac patients

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11
Q

Where is thiopentone used?

A

Use in obstetrics

It is a potent myocardial depressant

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12
Q

What receptor does ketamine act on?

A

The NMDA receptor

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13
Q

What is a side effect of ketamine?

A

It causes a dissociative state and can cause vivid nightmares
Also causes memory suppression so maybe used in children

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14
Q

What are some advantages to inhalational induction agents?

A

Provides a large amount of control
Easier to control adverse CV and respiratory effects
Stopping allows for quick clearance of the agent
Good is cannulation may be difficult- children, needle phobic

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15
Q

What is a common inhalational agent?

A

Sevoflurane

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16
Q

What relationship is there for solubility of induction agents and how quick they work?

A

The less soluble a drug is the quicker it works-

This is because less agent i needed to saturate the blood and then levels of the agent in the brain increase, causing general anaesthesia

17
Q

What are some disadvantages to inhalational agents?

A

Speed of onset is dependent on rate and depth of breathing
Requires skill and attention to do it well
Must have good co-operation with patient

18
Q

When are inhalational anaesthetics commonly used?

A

Inhalational agents are commonly used for maintenance anaesthesia following induction

19
Q

What is a dangerous stage of induction for patients for inhalational agents?

A

Stage 2- The induction phase/Delerium Phase

This is because patients can vomit and choke and this can increase the risk of aspiration and death

20
Q

What are some important physical properties of inhalational anaesthetics?

A 
Non flammable
Stable in light
Liquid and vapourisable at room temperature
Non irritant to the airways
Pleasant to inhale
21
Q

What is seen with overdose of inhalational agents?

A

Medullary paralysis

Pupillary dilation
Respiratory Arrest
Cardiac arrest
Death

22
Q

Why is a lower solubility more desirable for inhalational anaesthetics?

A

Low solubility means that it takes less time for the anaesthetic to have it’s effect as the delay to saturating the blood is reduced if the anaesthetic is less soluble

23
Q

What is the minimal alveolar concentration?

A

This is the concentration of the anaesthetic in the alveoli required to produce immobility in 50% of patients when exposed to noxious stimuli

Or the concentration that prevents movement in response to skin incision is 50% of unpremeditated animals

24
Q

How can the alveolar concentration be estimated during surgery?

A

Using the expiratory concentrations of the anaesthetic agent

25
Q

What is MAC basically equivalent to?

A

The potency of the anaesthetic agent

If a higher MAC then it is less potent as more is need for analgesia in 50% of patients.

26
Q

What is the chemical formula of nitrous oxide?

A

N2O

27
Q

What are some inhalational agents?

A 
Nitrous oxide
Sevoflurane
Halothane
Isoflurane
Desflurane
28
Q

What are some risks with nitrous oxide?

A

Diffuses into air space and can expand- nitrogen air embolism

Diffusion into the stomach in babies can cause it to expand

29
Q

When in entonox commonly used?

A

Labour
Trauma
Children

30
Q

What is entonox?

A

A 50% mix of nitrous oxide and 50% oxygen

31
Q

Why is halothane not commonly used anymore?

A

Halothane hepatitis- it can cause liver injury which carries a high risk of mortality

Less common in children and is still used in children

32
Q

What is the most widely used inhalational agent?

A

Sevoflurane

It is non-irritant and doesn’t have much of an oddur. Can give rapid induction and it’s CV stable.

33
Q

What are some advantages to inhalational agents?

A

Easily reversible
Don’t require IV access- children and needle phobic
Predictable behaviour

34
Q

What are some disadvantages to inhalational agents?

A

Taken up in fat
Potential toxicity (especially hepatic toxicity)
Recovery requires ventilation so i there is any respiratory suppression this will be problematic

35
Q

What is TIVA?

A

Total Intravenous anaesthesia

36
Q

What does TIVA involve?

A

Induction dose is given to induce anaesthesia rapidly

Then a continuous infusion follows for maintenance

37
Q

What are some disadvantages to TIVA?

A

Cannula must stay in the vein- if this falls out no anaesthesia is being delivered
Can give unpredictable wake up times
Requires accurate syringe pumps
If fluids being given at the same time but be careful to use a special set to prevent anaesthetic agent entering fluids set

38
Q

Why is it difficulty to maintain anesthesia with recurrent bolus injections?

A

Very difficult to keep within the therapeutic range for this method

39
Q

What is an issue with a fixed infusion for anaesthesia?

A

Slow to induce anaesthesia or if rate of infusion is increased it can lead to toxicity and overdose

SPC- Anaesthetics (7 decks)

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