Anaesthetics - Analgesia

Question 1

What is pain?

Answer 1

An unpleasant sensory/emotional experience associated w/ actual/potential tissue damage OR described in terms of such damage

Question 2

How is pain transmitted?

Answer 2

A-delta fibres = sharp, immediate pain
C-fibres = slower onset, prolonged pain
Sensory impulses enter cord via dorsal root, ascend in dorsal post column/spinothalamic tract

Question 3

What are the adverse effects of pain?

Answer 3

Multiple psychological effects
Catecholamine release
-vasoconstriction –> inc cardiac work/delayed healing

Question 4

What is the WHO pain ladder?

Answer 4

Non opioid +/- adjuvant
Weak opioid +/- non-opioid +/- adjuvant
Strong opioid +/- non opioid +/- adjuvant

Question 5

What is the MoA of Paracetamol?

Answer 5

Unknown

• acts similar to NSAIDs
• inhibits CNS prostaglandin synthesis

Question 6

When is Paracetamol indicated?

Answer 6

Mild-mod pain

Pyrexia

Question 7

What are the benefits of Paracetamol?

Answer 7

Good analgesic/antipyretic properties
Weak anti-inflame activity
Oral doses achieve PPC w/i 1hr
Side effects uncommon

Question 8

What is the dose of Paracetamol?

Answer 8

1g PO/IV QDS

• max of 4g/day
• dose reduced in pts <50kg
• max of 3g/day if risk factors for hepatotoxicity

Question 9

What is the MoA of NSAIDs?

Answer 9

Inhibition of COX enzymes (produce PGs/TXA2)

• COX-1 = expressed in most tissues, platelet aggregation, renal blood flow autoregulation, GI production
• COX-2 = induced in active inflame cells, sensitises nociceptors/afferent pain fibres

Question 10

What are the benefits of NSAIDs?

Answer 10

Anti-inflammatory/analgesic effects

Weak antipyretic effect

Question 11

When are NSAIDs indicated?

Answer 11

Inflammatory pain

Question 12

What are the side effects of NSAIDs?

Answer 12

Inhibition of COX-2

• dyspepsia & gastric ulceration
• bronchospasm
• renal insufficiency
• cardiotoxicity
• dec platelet count
• skin reactions

Question 13

What are the absolute contraindications to NSAIDs?

Answer 13

Severe heart failure

History of GI bleeds/ulceration

Question 14

What are the cautions to NSAIDs?

Answer 14

Asthma
Elderly
Coagulopathies
Renal/hepatic/cardiac impairment

Question 15

What are the doses of NSAIDs?

Answer 15

Ibuprofen 400mg QDS

• co-prescribe PPI w/ NSAIDs
• can be oral/topical

Question 16

What are coxibs?

Answer 16

COX-2 selective inhibitors

• licensed for use in RA/OA
• 1st line for thrombocytopenia/high risk of GI comp
• still co-prescribe PPIs

Question 17

What is the MoA of opioids?

Answer 17

Act on u-opioid receptors in CNS/throughout body, decreasing neuro-excitability
-not effective in neuropathic pain

Question 18

What are the side effects of opioids?

Answer 18

Resp depression
N/V (40%)
Constipation
Sedation/depression of cough reflex
Gall bladder concentration

Question 19

What are the absolute contraindications to opioids?

Answer 19

Acute resp depression
Acute alcoholism
Risk of paralytic ileus
Raised ICP

Question 20

How should morphine be prescribed in the acute setting?

Answer 20

Healthy adults = 5mg IV, titrate up

Elderly = 2mg IV, titrate up

Question 21

What drugs should be co-prescribed w/ morphine?

Answer 21

Metoclopramide 10mg IV TDS
Senna
Lactulose

Question 22

How are opioid doses converted?

Answer 22

Convert all opiate doses into oral morphine equivalence
Total 24hr dose
Divide into 2h modified release doses of Zomorph
Prescribe 1/6th total daily dose prn Oramorph

Question 23

How should opioid overdose be managed?

Answer 23

400 mcg Naloxone IV
-if no response after 1min give 800mcg
-if no response after 2min give 800mcg
2mg/4mg doses given in severely poisoned pts

Question 24

What are the indications for PCA?

Answer 24

Post-op

Palliation in oncology

Question 25

What is PCA?

Answer 25

Syringe driver allowing boluses of painkiller to be delivered on patient demand

• locks out for a set time
• can be set to provide continuous background dose

Question 26

What are the options for non-drug analgesia?

Answer 26

Splinting
Cold therapy
TENS
Acupuncture
CBT