Pain Management

Question 1

8 months post amputation a patient presents with intermittent pain in limb. Impacting on his daily living. What is your management?

Answer 1

Step by Step approach to pain: 1) Non-pharm: - PT - CAM acupuncture/chiro/massage - psychoeducation (neuropsych) 2) Medications: - WHO Pain Ladder - non-opioid (NSAID) - opioid (codeine/oxycodone) - morphine/hydromorphone - Adjuvants: - antidepressants - anticonvulsants 3) Surgical - peripheral ablation (nerve block) - direct delivery (implantable morphine) - central ablation - DBS (dorsal column stimulation)

Question 2

Briefly Describe the Pathophysiology of Pain.

Answer 2

nociceptors sense pain (2 types - alpha delta (fast sharp), c fibres - slow poorly localised) through dorsal to the spinothalmic tract (crosses over) goes to the thalamus - 3rd order (right side processes in left side of the brain).

Question 3

Discuss how pain can be classified?

Answer 3

Chronicity - acute (usually <6days) - subacute (3-12weeks) - chronic >3 months Aetiology - nociceptive (visceral, somatic) - neuropathic - psychogenic -mixed Function - adaptive - maladaptive Other - cancer pain - breakthrough pain - incident pain - abnormal pain

Question 4

Explain the WHO Pain Ladder

Answer 4

0) Rx underlying cause 1) Non-opioids ± adjuvants a. Paracetamol b. NSAIDs 2) Opioids for mild-moderate pain (formerly “weak opioids”) 3) Opioids for moderate-severe pain (formerly “strong opioids”) – discontinue regular dose weak opioid 4) Adjuvants a. Steroids b. Antidepressants = TCAs, SSNRIs c. Anticonvulsants = carbamazepine, valproate, pregabalin d. Ketamine = (NMDA antagonist)

Question 5

What are some prescribing rules for Opioids?

Answer 5

Prescribing Rules Prescribe opioids → must rx SE □ Constipation → laxitives □ Nausea → metoclopramide, ondansetron □ Delirium Remember the ABCs A) Anti-emetics B) Breakthrough pain C) Constipation - renal impairment use fentanyl (metabolites inactive) - liver impairment oxycodone/hydromorphone and avoid targin (as naloxone more likely systemic) 1) Start with Short Acting (4 hourly and base dose) (can be long) and 1/2 dose in renal or hepatic impairment 2) Use breakthrough analgesia (>30mins ago for last dose) 3) Next day regular dose (count up all throughout day and divide by 6) - no ceiling dose in palliative care. 4) Once stabilises use 12 hourly long acting in equivalent dose 5) rotate opioid is necessary (calculate morphine dose and convert with allowing for safety margins)

Question 6

Side effects of opioids?

Answer 6

Nausea can sometimes spark vomiting - treat with drugs N - nausea C - constipation (+ urinary retention) S - sweating S - sedation V - vomiting T - tolerance W - withdrawal D - dependence/delirium others - itch, myoclonus, anaphylaxis

Question 7

List the long acting and short acting Opioids.

Answer 7

Long Acting: - MS contin - oxycontin - codeine contin - fentanyl patch - hydromorphone jurnista Short Acting: - morphine - oxycodone/endone - codeine - fentanyl lozenge - dilaudid

Question 8

List some adjuvant analgesics and when you’d think to use them?

Answer 8

• Steroids (dexamethasone) - stops swelling - Antidepressants - amitriptyline and venlafaxine - anticonvulsants (pregabalin (sciatica), carbamazepine (trigeminal neuralgia), sodium valproate (in elderly) - ketamine - NMDA receptor, but toxicity.

Question 9

What are some non-pharmalogical ways to manage chronic pain?

Answer 9

Comfort Measures: Mind-based therapy: - music - distraction - social activities - pet therapy Physical - hot/cold packs - Transcutaneous electrical nerve stimulation - acupuncture - physio - massage Psychological - Education - Relaxation - CBT

Question 10

Overview the Opioids?

Answer 10

1st line is generally morphine

hydromorphone:

• stronger

oxycodone

• slightly stronger
• targin is used often (naloxone + oxycodone)

fentanyl

• used 1st line in kidney - less constipating

buprenorphone

• used in palliative care

Dosing:

> 3 breakthrough doses in 24 hours increase the dose by 10%

MCQ on converting opioid dosing

• IV to oral is 1-3
• oral oxycodone to IV morphine (1:2)
• oral morphine to IV morphine 1:3
• oral to oxycodone 1:1.5
• hydromorphone is 1:5

Side Effects of Opioids: common - true sign of allergy

• constipation - laxatives required too
• N+V (PRN anti-emetic)
• sedation
• respiratory depression
• cognitive impairment/neurotoxicity
• rigidity
• itch
• dry mouth