Mechanisms of Anaesthesia Flashcards

1
Q

Which type of analgesia blocks nerve conduction?

A

Local anaesthetics

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2
Q

Where do delta receptors act as analgesics?

A

Spinal

Peripheral

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3
Q

Which type of opioid receptors are associated with sedation dysphoria and hallucinations?

A

Kappa

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4
Q

What are the respiratory effects of opioids?

A

Apnoea

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5
Q

What are the cardiovascular effects of opioids?

A

Orthostatic hypotension

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6
Q

How can morphine cause asthma attacks?

A

Causes mast cell degranulation which triggers bronchospasms

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7
Q

How do opioids cause nausea?

A

Act on CTZ outside the BBB

Decrease motility via enteric neurons via mu and delta receptors

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8
Q

What are the GI side effects of opioids?

A

Nausea
Vomiting
Constipation
Increased intrabilliary

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9
Q

What are the CNS effects of opioids?

A

Confusion, euphoria, dysphoria, hallucinations, dizziness, myoclonus

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10
Q

How is morphine metabolised?

A

Glucorinidation at 3 and 6 position to M3G and M6G

M6G excreted by the kidney

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11
Q

Which is the active metabolite of morphine?

A

M6G

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12
Q

Is oxycodone more/less potent than morphine?

A

3x more

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13
Q

What is diamorphine mostly used for?

A

Severe post op pain

Labour

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14
Q

Which is more lipophilic morphine or diamorphine?

A

Diamorphine

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15
Q

What is codeine metabolised to and how?

A

Via p450s in hepatic metabolism

To morphine

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16
Q

How is fentanyl given?

A

IV

Transdermal or buccal in chronic pain

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17
Q

How do opioids works as analgesics?

A

Act to open inhibit VGCCs and open K+ channels on projection neurons of nociceptors

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18
Q

Which receptor is responsible for most of the analgesic action of opioids?

A

Mu

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19
Q

Describe the onset of action of pethidine

A

Rapid (when given IV, IM, s/c)

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20
Q

Which metabolite of pethidine causes seizures?

A

Norpethidine

21
Q

What is the problem with use of pethidine in labour?

A

Very potent so causes resp depression in babies

22
Q

What is buprenorphine?

A

Long acting partial agonist of opioids

23
Q

How is buprenorphine administered?

A

Injection

Sublingual

24
Q

What is tramadol

A

Weak mu opioid receptor agonist

25
Q

What is though to be the main mechanism of action of tramadol?

A

Potentiates the descending serotonin system

And adrenergic system from the LC

26
Q

Other than opioid receptors where does methadone act?

A

K channels
NMDAR
5HT recs

27
Q

How is methadone administered?

A

Oral

28
Q

What is methadone used for?

A

Addiction

Cancer

29
Q

What is naloxone?

A

Competitive antagonist of mu receptors (kappa and delta a lil)

30
Q

What is naloxone mainly used for?

A

Reversal of opioid toxicity

31
Q

Why does the use of naloxone in opioid overdose need to be monitored?

A

Has a short half life

Some opioids still acting

32
Q

What are alvimopan and methylnaltrexone used for?

A

Reduce the GI effects of chronic opioid use

33
Q

Outline the mechanism of action of NSAIDs

A

Inhibits COX-1 and COX-2 to reduce the synthesis and accumulation of prostaglandins

34
Q

Outline the production pathway of prostaglandins

A

Phospholipids converted to arachidonic acid by phospholipase A
Arachidonic acid converted to endoperoxides which COX1 and 2
Endoperoxdies to prostaglandins isomerase
Prostaglandin isomerase to prostaglandins

35
Q

Which group of drugs selectively inhibids COX-2?

A

coxibs

36
Q

Why is COX2 sometimes selectively inactivated?

A

Bc COX2 is induced locally at sites of inflammation by various cytokines

Most of the therapeutic benefit comes from this

37
Q

What do NSAIDs decreased recruitment of?

A

Leukocytes

38
Q

What occurs if NSAIDs cross the BBB?

A

suppress the production of pain producing prostaglandins in the dorsal horn

39
Q

Why do NSAIDs have limited analgesic activity?

A

Multiple signalling pathways do not involve arachidonic acid metabolism

40
Q

What might long term administration of non-selective NSAIDs cause?

A

GI damage

Nephrotoxicity

41
Q

Why do kidneys get damaged with NSAIDs?

A

COX-2 constitutively expressed by kidney

42
Q

Why is the use of coxibs limited?

A

They are prothrombotic

43
Q

What is the proposed pathology behind neuropathic pain?

A

Down regulation of mu opioid receptors following injury

44
Q

How does gabapentin act?

A

Reduces cell surface expression of an alpha2delta-1 group in the VGCC of sensory neurons
To decrease the weirdly high amount of neurotransmitters released

45
Q

What is the first line treatment of neuropathic pain?

A

Tricyclic antidepressants

46
Q

Give examples of tricyclic antidepressants

A

Amitriptyline
Nortryptyline
Desipramine

47
Q

How do tricylic antidepressants work?

A

Act centrally by decreasing the reuptake of noradrenaline (and 5HTfor venlafaxine)

48
Q

How does carbamazepine work?

A

Blocks VGNCs which are upregulated in damaged nerve