Chronic Pain & management

Question 1

Definition of chronic pain

Answer 1

Pain which persists beyond the healing phase, which may be due to progressive or sustained tissue damage but may also be due to a mechanism within the nervous system itself –> can also arise from purely psychological causes

Question 2

Classification of analgesics

Answer 2

Non-narcotic –> act peripherally – COX inhibitors
Narcotic –> CNS – opiates
Adjuvant –> modify underlying cause, or modify perception of pain

Question 3

Adjuvant analgesics include

Answer 3

amitriptylines, carbamazepine, gabapentin

Question 4

Opioids used in chronic pain (6)

Answer 4

Morphine, oxycontin, fentanyl, buprinorphine, meptazinol, methadone

Question 5

Concerns about long term opioid use (5,5)

Answer 5

Common – sedation, nausea, vomiting, constipation, urinary retention
Emerging –Immune dysfunction, endocrine deficiency, sleep disorders, hyperalgesia, race/sex/age variability

Question 6

Indications for using opiates in chronic pain (5)

Answer 6

The pain is a major impediment to recovery and psychological issues are not a major concern
Other drugs have failed
No history of substance abuse
Will always require monitoring

Question 7

Tricyclic antidepressants as adjuvant analgesics

Answer 7

Block 5HT & NA reuptake
Rapidly absorbed and bound to albumin, metabolised in liver and have a long half life
SEs–> anticholinergic, CNS depression/agitation, CVS effects (cardiotoxicity, hypotension)

Question 8

How do antidepressants work as adjuvant analgesics?

Answer 8

Stimulate the descending inhibitory pain pathway
Work in non-depressed patients
Amitripyline is best

Question 9

Anticonvulsants which are used as adjuvant analgesics

Answer 9

Carbamazepine, sodium valproate, lamotrigine, gabapentin, clonazepam, topiramide, pregabalin

Question 10

Injections for chronic pain

Answer 10

Diagnostic – LA to clarify mechanism or simulate effect
Therapeutic – temporary (LA) or permanent (lytic agent) injections to disable a pathway or reduce inflammation (corticosteroids)
Both – sympathetic block or trigger-point injection

Question 11

Trigger point injections

Answer 11

A taut band of muscle with a tender point – pain is reproduced by stretch and pressure –> pain by a referred to another point
Can use just a needle, LA, LA+glucocorticoid, or botox

Question 12

Peripheral nerve injections

Answer 12

For spontaneous entrapment syndromes (ilioinguinal, lateral femoral, greater occipital) or post-traumatic neuroma –> inject LA+glucocorticoids

Question 13

Paravertebral nerve root injection

Answer 13

Used in cases of disc disease or foraminal stenosis

Deposit LA+glucocorticoid and use CT/fluoroscopy to validate

Question 14

Selective lumbar nerve root block

Answer 14

Inject around a lumbar nerve root to block transmission of pain

Question 15

Epidural injection

Answer 15

Allows for symptomatic relief in disc protursion with radiculopathy, spinal stenosis, pain from vertebral #,
Can help rehabilitation or to avoid surgery

Question 16

Intra-articular injection

Answer 16

Used in large facet joints, most commonly sacroiliac

Use LA+Glucocorticoid injection to reduce pain/inflammation but results contraversal

Question 17

Radiofrequency ablation

Answer 17

Can be very effective in treating facet joint degeneration permanently – should only be used after successful blocks prove the cause of the pain

Question 18

Sympathetic block

Answer 18

Can use LA or neurolytics to treat Facial neuralgias or CRPS

Question 19

Plexus blocks

Answer 19

Both sympathetic (coeliac) and parasympathetic (hypogastric) afferent visceral nociceptive pathways
Limited evidence of efficacy (abdo cancers)
Can use LA or neurolytic

Question 20

Spinal cord stimulator

Answer 20

Uses ‘gate theory’ to reduce pain by increasing peripheral electrical stimulation. Used for neuropathic limb pain, CRPS

Question 21

Implanted analgesic pumps

Answer 21

A large variety of agents to treat both pain and spasticity

opiods, LAs, NSAIDs, CCBs, NMDA blockers, and more

Question 22

Arntz & Claasens 2004

Answer 22

showed that pts views of how painful something was depended on their beliefs about how damaging it was.
Links into a bio-psychosocial model of pain

Question 23

Neuropathic pain

Answer 23

Pain which arises from damage or disruption of the nervous system. Often responds poorly to standard analgesia and is difficult to treat

Question 24

Examples of neuropathic pain syndromes

Answer 24

Diabetic neuropathy
Post-herpetic neuralgia
Trigeminal Neuralgia
Prolapsed intervertebral discs

Question 25

Management of Neuropathic pain

Answer 25

1st - Amitriptyline, duloxetine, gabapentin or pregabalin
–> if unresponsive try another
2nd - Tramadol can be used as a ‘rescue therapy’ in acute exacerbations or Topical capsaicin if localised (post-herpetic)
If resistent refer to pain clinics

Question 26

Trigeminal Neuralgia

Answer 26

Severe, unilateral (electric-like) pain invoked by light touch which is usually idiopathic but can be due to vascular problems or tumours. May have trigger areas. abrupt onset and offset. remitting and relapsing course

Question 27

Post herpetic Neuralgia

Answer 27

Most common complication (20%) of shingles. Chronic pain along cutaneous nerves. Can persist after shingles or recur later in an area previously affected by shingles. More common in older women or if shingles was severe. Risk if greatest in trigeminal area (ophthalmic) and brachial plexus. lasts 1-4months. Will be hypersensitive and can last for years.

Question 28

Treatment of trigeminal neuralgia

Answer 28

First line is carbamezapine. If this is not effective or there are atypical features (<50yrs) should be referred to neurology.

Question 29

Treatment of Post herpetic Neuralgia

Answer 29

First line is with cocodalmol low dose amitriptyline (10-25mg) or gabapentin (300mg) can also be used. topical capsaicin or LA patchs may also help. booster VZV vaccines can also help prevent shingles