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BAB > L22: General Anaesthetics > Flashcards

L22: General Anaesthetics Flashcards

1
Q

What is the triad of general anaesthesia

A

Need unconsciousness
Need for analgesia- pain relief
Need for muscle relaxation for loss of reflexes

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2
Q

what is the lipid theory of anaesthesia about

A

The concentration of agent required to immobilise tadpoles is inversely proportional to lipid:water partition coefficient. This means that a low concentration of GA agent is required if its lipid soluble.

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3
Q

How do general anaesthetic action work through

A

Depressing CNS activity

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4
Q

What is the anaesthetic concentration in the cell membrane for any agent to show an effect

A

0.05m

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5
Q

What has to happen to the volume of lipid for anaesthesia to occur

A

Expand by 0.4%

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6
Q

What is the protein theory for general anaesthetics about

A

Lipid solubility is required to access/target the proteins (ion channels/receptors)

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7
Q

What is the cut off phenomenon

A

As the chain length of the GA increases lipid solubility increases so potency (ability to bind to receptor) increases however after a certain length the potency stops as the size of the GA is important because it has to fit somewhere

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8
Q

What is steroselectivity of GA about

A

Potency is preserved with protein binding as GA bind to hydrophobic pockets within the cell membrane of proteins

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9
Q

What are the 2 main targets of ion channels/receptors for inhaled GA

A
  • GABAa receptors

- potassium channels

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10
Q

When GABAa receptors are activated which neurotransmitter is released

A

GABAa

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11
Q

What type of neurotransmitter is GABAa

A

Inhibitory neurotransmitters

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12
Q

What does GABAa do to the cns

A

Depression

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13
Q

What does potassium channel activation lead to

A

Hyperpolarization

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14
Q

What does hyperpolarization lead to in the cns

A

Depression

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15
Q

What channels are inhibited with GA

A

Excitatory channels of:
NMDA
5HT
ACH nicotinic

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16
Q

Why does the CNS become depressed

A

Due to decrease in neurotransmitter release and transmission

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17
Q

What structure is suppressed that leads to unconsciousness

A

Reticular formation in the midbrain

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18
Q

Which structure is suppressed that causes analgesia

A

Thalamus

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19
Q

What structure is suppressed that causes loss of reflexes

A

Spinal cord

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20
Q

What happens at a low concentration of anaesthetics

A

No one can form memory

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21
Q

What happens with a small increase in anaesthetic concentration

A

Consciousness decreases

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22
Q

What happens with a higher concentration of anaesthesia

A

Loss of motor reflexes i.e movement

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23
Q

What happens at the highest concentration of anaesthesia

A

Inhibition of the cardiovascular respiratory response which can lead to death

24
Q

What is the therapeutic window between suppressing movement and inhibiting the cardiovascular respiratory response like

A

Narrow

25
Q

What are the 4 stages of anaesthesia

A

1) analgesia
2) delirium
3) surgical anaesthesia
4) medullary paralysis

26
Q

What occurs in the analgesia stage

A

Drowsiness
Reflexes intact
Still concisous
Pain is still felt

27
Q

What happens in the delirium stage

A

Excitement
Delirium
Incoherent speech
Unresponsive only to non-painful stimuli

28
Q

What phase can occur during the delirium stage

A

Dangerous phase

29
Q

What does the dangerous phase involve

A

Cardiac arrthymias
Vomiting
Chocking

30
Q

What occurs in the surgical anaesthesia stage

A

Patient is:

  • unresponsive to painful stimulus
  • Regular breathing
  • muscle relaxation
31
Q

What occurs in the medically paralysis stage

A

Pupillary dilation
Respiration and circulation declines
EEG waves
Death

32
Q

Why can the medically paralysis stage occur

A

Due to overdose

33
Q

What are the 2 characteristic that make a good general anaesthetics

A

Potent

Fast acting

34
Q

What is potency measured by

A

MAC (minimal alveolar concentration)

35
Q

What is MAC

A

Concentration of anaesthetics in the alveoli required to produce immobility in 50% of patients when exposed to noxious stimulus

36
Q

What is MAC inversely proportionate to

A

The lipid solubility

37
Q

What does it mean if MAC is inversely proportionate to lipid solubility

A

If the GA has a high lipid solubility less concentration of MAC is required to produce anaesthesia

38
Q

What is fast acting about

A

Speed of induction

39
Q

Why do we want a fast acting ga

A

When we go through the delirium stage if a dangerous phase occurs it will allow a faster recovery

40
Q

Where does GA work in the body

A

Brain

41
Q

What are the 2 ways to increase transfer of GA to the alveoli

A
  • Increase the anaesthetic conc in gas as you are breathing in
  • increase the rate and depth of breathing as you are getting the agent into your body faster
42
Q

What are the way in which you can increase the speed of induction from transfer to blood to the brain

A
  • give a relatively blood insoluble gas so the blood saturates quickly and agent transfers to brain faster i.e a lower blood:gas partition coefficient
  • higher cardiac output means faster transfer
43
Q

What are the factors that can increase/decrease the speed of induction of GA from blood to tissue

A
  • obese patients will have higher adipose tissue which has a high capacity for GA, therefore this will slow down the speed of induction
  • lean tissue mass has a higher blood flow so this will allow a faster transfer
44
Q

What are the 2 ways in which we can eliminate GA

A
  • breathe it back out via the lungs

- metabolism of GA

45
Q

What is a balanced anaesthesia

A

Using a combination of different drugs for optimal clinical effect with lowest risk

46
Q

When is intravenous anaesthesia used

A

For short proceeds or for induction of anaesthesia so you can maintain the rest by inhalation

47
Q

What receptors does intravenous anaesthesia work on

A

GABAa receptros

NMDA receptors antagonist

48
Q

What are the 3 broad adjuvants i.e add ons to anesthesia that are used

A

1) pre medication
2) muscle relaxants
3) anti-emetics

49
Q

What types of drugs are used as pre-medications

A

Benzodiazepines
Opioids
Anti muscarinics

50
Q

What are benzodiazepines used for

A

Sedation
Reduce anxiety
Amnesia

51
Q

What are opioids used for

A

Pain relief

52
Q

What are anti muscarinics used for

A

Facilitate intubation and ventilation by relaxing smooth muscle

53
Q

Why are muscle relaxants used

A

To relax deep abdominal, tracheal, diaphragm muscles without the need for deeper anaesthesia so you can use a reduced dose of GA and prevent overdose

54
Q

What are the types of drugs used as muscle relaxants

A

Benzodiazepines

Neruomuscular blockers

55
Q

Why are anti-emetics used

A

To decrease peri-operative nausea and vomiting

56
Q

Give an example of a anti-emetic

A

Metocloprimide

BAB (21 decks)

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