Pain assessment and management Flashcards
Different types of pain
- Nociceptive: arises from direct activation of nociceptors located in the peripheral somatosensory nervous system. Can be visceral where received from internal structures such as GI tract causing crampy/dull non localised pain. Can be somatic where received from skin/bone/muscle causing sharp/aching/throbbing well localised pain
- Neuropathic: occurring with a abnormally functioning somatosensory nervous sytem due to compression/ischaemia/transection of a nerve or abnormal signalling which magnifies the response to a stimulus - resulting in burning, tingling, shooting, stabbing, electric like pain
40% are mixed
Incident: also known as breakthrough pain when related to movement such as walking/sitting/intestinal. A transient exacerbation of pain with a background of persistent usually adequately controlled pain. Is a quick onset <3mins of severe intensity but brief duration <30mins
Prescribing analgesia:
- Factors that determine opioid selection
- Preparations
- SE
- Safe prescribing
- Anxieties of patient commencing morphine
- Meds for bone mets, liver pain
Prescribing analgesia:
- Factors which determine opioid selection: adverse effects, available route of administration, combination formulation opioid, remember fentanyl patch takes 12-24 hours to achieve steady state
- Preparations: immediate release if contin pain and can achieve steady state within a day. Can use extended release meds over 8, 12, 24 hours and due to longer half life takes 2-4 days to work. For breakthrough dosing can give extra dose analgesia so consider intermediate release preparation opioid of which they use for routine dosing - but if they need this lots then consider increasing routine dose.
- SE:
nsaids: gi upset, renal failure, inhibits platelet aggregation
opioids: common ongoing - constipation, dry mouth. Common initial: sedation/cognitive impairment, N+V
- Safe prescribing: physical withdrawal symptoms so taper doses, administer at regular intervals, oral route when feasible, back up with doses for break through pain, monitor benefit, treat SE (laxative laxido 1 sachet prn + antiemetic (metoclopramide 10mg PRN)
- Anxieties of pt commencing morphine: addiction, tolerance, last resort, side effects
- Meds bone mets respond to, liver pain responds to: for bone mets nsaids, radiotherapy, bisphosphonates. If liver pain steroids/nsaids.
- Ceiling effect: drug reaches a max effect where increasing the dose no longer increases effectiveness
- Titrating opioids:
Codeine phosphate 30mg tablets (codeine: morphine 10:1) therefore 240mg codeine = 24mg morphine in 24 hours TDD. When prescribing starting dose of morphine needs to give greater analgesia effect than med currently in use
Morphine forms:
1. oromorph - liquid 10mg/5ml (immediate release)
2. zomorph capsules BD 10, 30, 60, 100, 200mg (slow release)
3. SC
Add up 24 hour use of morphine sulfate = TDD total daily dose
TDD/2 = slow release regular dose
TDD/6 = immediate release breakthrough dose
Oral: SC 2:1
Oral: IV 3:1
What causes pain in cancer
- Tumour invasion of bone, nerve, meninges and spinal cord
- Pain associated with cancer therapy - post surgical, post chemo (peripheral neuropathy e.g.), post radiation
- Unrelated to neither above - something else
Assessment
- History - including verbal/visual analogue pain scales
- Examination
- Investigations
- Psychosocial assessment
- Addiction screening
Adjuvant analgesics:
- When to introduce
These are drugs whose primary indications is not for pain. But neuropathic pain as they are less responsive to standard analgesics alone
This includes:
- Steroids: dexmethasone, if compression of nerves or intracranial pressure
- Antidepressants: amitriptyline (start 10-25mg, confusion, hypotension, careful if cvs disease), duloxetine SNRI
- Benzodiazepines: diazepam
- Anticonvulsants: gabapentin (300mg tds over 3 days), pregabalin (75mg BD, sedation, tremor, confusion, dizzy, careful if renal impairment)
- Bisphosphonates: pamidronate
Non pharmacological management
- Physical therapy - massage, trigger point manipulation
- Radiation therapy
- Surgery
- Psychological, sociocultural and spiritual management
- Anaesthetic and neurosurgical approaches - local anesth blocks
WHO performance status
- Definition
- Classification
- Definition: categories pts into different groups depending on their physical fitness and is used to categorise their suitability for chemo (otherwise signif SE if <3
- Classification:
- 0 - able to carry out normal without restriction
- 1 - restricted in strenuous activity
- 2 - unable to carry out work activities
- 3 - symptomatic, in chair/bed over >50% day
- 4 - bedbound, no self care
Why is pain bad
impairs function
threaten independance
invokes fear of further suffering / dying
3 step WHO ladder
Titrate up!!!
1. Non opioid analgesics 1-3/10 - paracetamol (can give 1g but not if <50kg), nsaids (usually used in full dose)
2. Weak opioids 4-6: consider that dehydration/renal failure impairs renal clearance so lower dose, if hepatic function impaired also need to decrease dose. Tramadol, codeine, hydrocodone, dihydrocodeine. Can argue there’s no need for weak opioids in cancer as morphine provides quick/better relief
3. Strong opioids 7-10: morphine, fentanyl, methadone, hydromorphone, oxycodone however bigger SE risk
