Analgesia Flashcards
1
Q
What is the definition of pain?
A
An unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage.
2
Q
Describe (P)RAT.
A
- Prevent - it is important to prepare a patient for any pain you will inflict as their doctor.
- Recognise
- Assess
- Treat
3
Q
Which questions must you ask yourself before you inflict pain on a patient?
A
- Do I need to do this?
- Can I do it skillfully and quickly?
- Can I minimise the pain?
- Pre-emptive analgesia (anticipate pain).
4
Q
List non-pharmacological techniques of pain management.
A
- Treat the underlying cause (eg. reduce / immobilise the fracture).
- RICE (cold pack for first 72 hours post minor MSK injury).
- Explanation / education / reassurance.
- Change of focus away from pain (distraction).
- TENS
- Hypnosis
- Acupuncture
5
Q
What is step 1 on the reverse WHO ladder?
A
- Mild pain
- Continue simple analgesics
6
Q
What is step 2 on the reverse WHO ladder?
A
- Moderate pain
- Use mild opioid eg. codeine, tramadol.
- Continue simple analgesics.
7
Q
What is step 3 on the reverse WHO ladder?
A
- Severe pain
- Use strong opioid eg. morphine.
- Also continue to use simple analgesics.
- Start at this level for acute nociceptive pain. Go down the ladder as the patient gets better and the pain decreases.
8
Q
Which questions must you ask yourself before pescribing?
A
- Which drug am I going to give this patient for this problem?
- Which route am I going to give it by?
- What dose? (What weight is the patient, is there a reason to reduce the dose?)
- How often? (Are the kidneys working? Increase length of dose if you are worried about renal function) Regularly or as required?
- Any adjuvant prescribing required?
- When prescribing opioids, remember a laxative and possibly an antiemetic.
9
Q
What are the possible routes of administration for pain medication?
A
- Topical
- Oral
- IM injection
- IV infusion
- Lolipops
- Directly into the CNS (dose is much smaller)
- Transcutaneous
- Per rectum
10
Q
What are the properties of paracetamol?
A
- Reduces pain (analgesic agent) and has anti-pyretic ability.
- Can be administered orally or per rectum.
- Effective within 40-60 minutes.
- Variable bioavailability.
11
Q
What are the properties of Falgan?
A
- IV paracetamol
- Onset within 5 minutes, peak effect at 40-60 minutes.
- Lasts 4-6 hours.
12
Q
Describe how paracetamol works.
A
- Paracetamol acts centrally in the brain, as opposed to the actual site of tissue damage.
- It acts on the peroxidase site, then have an effect on the cox enzymes.
- The end result is that is diminishes the amount of prostaglandins produced.
- It stimulates serotinergic pathway involved in descending inhibition.
- Pain is modulated in the dorsal horn. There is a descending inhibitory pathway which comes from the periaqueductal gray matter through the medulla and acts on the dorsal horn.
- It stimulates this inhibitory descending pathway.
- Third mechanism of action is the anti-pyretic effect.
13
Q
What are the positives of using paracetamol?
A
- SAFE AND EFFECTIVE
- Cheap
- Number needed to treat (compared to placebo) ~4 to achieve a >50% reduction in moderate pain over 4-6 hours.
- Safe in theraputic dosage.
- Synergistic effect with NSAIDs and opioids (allows less use of these).
- Antipyretic action but poor anti-inflamatory action.
14
Q
Describe the pharmacokinetics of paracetamol.
A
- Absorbed from the small bowel.
- High, but variable bioavailablilty.
- Metabolised in the liver.
15
Q
Describe the effects of paracetamol toxicity.
A
- Foremost cause of acute hepatic failure in the UK.
- Symptoms:
- <8 hours of nausea / vomiting
- 12-36 hours - usually no symptoms
- 24-72 hours - hepatic failure
16
Q
What is the treatment for acute hepatic failure secondary to paracetamol toxicity?
A
N-acetyl cysteine
17
Q
Describe the properties of NSAIDs.
A
- Anti-inflammatory
- Analgesic
- Anti-pyretic
- All of these actions are related to the primary action of these drugs:
- Inhibit prostaglandin biosynthesis by direct action on cyclo-oxygenase enzymes.
- Paracetamol has an indirect mechanism of action, NSAIDs are DIRECT.
18
Q
What is the mechanism of action of NSAIDs?
A
- All inhibit cyclo-oxygenase (COX) but do so by two main mechanisms:
- (1) - an irreversible, time-dependent inhibition of the enzyme (aspirin).
- (2) - A rapid, reversible competitive inhibition of the enzyme (the rest).
- Eg. ibuprofen, naproxen.
- Binds reversibly to the enzyme.
- Competes with natural substrate, arachidonic acid.
- Clinically, aspirin is most commonly used as an anti-platelet drug.
19
Q
What is Reye’s syndrome?
A
- A rare, but life-threatening disorder of children or young adults.
- Children under 16 should not take products containing aspirin.
- Usually occurs following a viral illness (+ingestion of aspirin).
- Persistent uncontrolled vomiting and altered consciousness.
- Still GCS15 but working really hard to orientate themselves.
- Derangement of liver enzymes.
20
Q
Describe prostaglandins.
A
- Inflammation is always accompanied by the release of prostaglandins.
- Predominantly PGE2 but also PG12.
- PGD2 from mast cells.
- PGE2, PG12 and PGD2 act as potent vasodilators.
- Also synergise with other inflammatory mediators (eg. histamine and bradykinin).
- Potentiate histamine and bradykinin actions on postcapillary venule permeability and pain sensory nerves.
