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Chronic Pain Again

Chronic Pain Again. Dr. MC Chu Anaesthesia and Intensive Care PWH. Agenda. Remember the cases last time? Bear in mind the complexity of chronic pain Let’s try to treat them. Treatment principles. Pain as a symptom Find the cause and fix it Pathology oriented Works well in acute pain

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Chronic Pain Again

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  1. Chronic Pain Again Dr. MC Chu Anaesthesia and Intensive Care PWH

  2. Agenda • Remember the cases last time? • Bear in mind the complexity of chronic pain • Let’s try to treat them

  3. Treatment principles • Pain as a symptom • Find the cause and fix it • Pathology oriented • Works well in acute pain • Well accepted by patient and doctor

  4. Treatment principles • Pain as a symptom • Find the cause and fix it • Works well here

  5. Treatment principles • Pain as a symptom • Find the cause and fix it • Does all headaches have a pathology?

  6. Treatment principles • Pain as a symptom • Control the symptom • Passive • Long term effects and side effects • Case specific • What are the options?

  7. Symptom control • Medications • Antipyretics (paracetamol) • NSAID • Opioids • Antidepressants • Anticonvulsants • Steroids, muscle relaxants, etc.

  8. Symptom control • Paracetamol • Effective in OA knees • Amadio Curr. Ther. Res. 1983 • Effectiveness ~ Ibuprofen • Bradley N. Eng. J. Med. 1991 • Safe and economical, NSAID sparing for elderly • Nikles Am. J. Ther. 2005

  9. Symptom control • Paracetamol • Evidence in OA only • Hepatic and renal toxicity do occur • Medication induced headache

  10. Symptom control • Medications • Antipyretics (paracetamol) • NSAID • Opioids • Antidepressants • Membrane stabilisers (anticonvulsants) • Steroids, muscle relaxants, etc.

  11. Symptom control • NSAID • Best evidence from rheumatoid arthritis • Also good for cancer pain • Effective in 5 out of 10 placebo-trials for LBP • Effective in 4 out of 9 Panadol-trials for LBP • Doubtful value for non-specific musculoskeletal pain • Koes Ann. Rheum. Dis. 1997 • Eisenberg J. Clin. Onco. 1994

  12. Symptom control • NSAID • Annual GI bleed risk: 0.8-18% / year • Annual death rate: 0.03-0.1% / year • MacDonald BMJ 1997

  13. Symptom control • NSAID • Risk increase with age, > 4 week use, • history of GI bleed / ulcer / CVS disease • Least damaging: Ibuprofen • Only effective prophylaxis: PPI • Yeomans N. Eng. J. Med. 1998

  14. Symptom control • COX-2 specific NSAID • You know what happened to your patients

  15. Symptom control • COX-2 specific NSAID • You know what happened to your shares?

  16. Symptom control • Medications • Antipyretics (paracetamol) • NSAID • Opioids • Antidepressants • Membrane stabilisers (anticonvulsants) • Steroids, muscle relaxants, etc.

  17. Symptom control • Opioids • Gold standard for cancer pain management • (mostly) cheap and readily available • Administered at every route

  18. Symptom control • Opioids • Controversial for non-cancer pain • Limited (but positive) evidence of efficacy • Extensive side effects • Tolerance • Dependence • Divergence

  19. Symptom control • Opioids • Controversial for non-cancer pain • “Physicians should make every effort to control indiscriminate prescribing, even under pressure from patients…” • Ballantyne N. Eng. J. Med. 2003

  20. Symptom control • Opioids • Controversial for non-cancer pain • “Opioids are our most powerful analgesics, but politics, prejudice, and our continuing ignorance still impede optimum prescribing” • McQuay Lancet 1999

  21. Symptom control • Opioids • Practical guidelines for non-cancer pain • Exhaust other methods • Aim at functional improvement • Limit prescription authority, monitor behavior • Slow release, avoid injectables • Opioid contract

  22. Symptom control • Medications • Antipyretics (paracetamol) • NSAID • Opioids • Antidepressants • Membrane stabilisers (anticonvulsants) • Steroids, muscle relaxants, etc.

  23. Symptom control • Antidepressants • Analgesic at below mood altering doses • NNT for diabetic neuropathy ~ 3.4 • Collins J. Pain & Sym. Manag. 2000

  24. Symptom control • Antidepressants • Analgesic at below mood altering doses • NNT for post-herpetic neuralgia ~ 2.1 • Collins J. Pain & Sym. Manag. 2000

  25. Symptom control • Antidepressants • How good is NNT of 2.1 to 3.4? • It is not good for this

  26. Symptom control • Antidepressants • How good is NNT of 2.1 to 3.4? • It is really good for pain

  27. Symptom control • Antidepressants • Major problem: side effects • NNH (minor) ~ 2.7 • No consensus which one is best • Classically TCA • SSRI: seemed more specific on mood

  28. Symptom control • Medications • Antipyretics (paracetamol) • NSAID • Opioids • Antidepressants • Membrane stabilisers (anticonvulsants) • Steroids, muscle relaxants, etc.

  29. Symptom control • Anticonvulsants • Carbamazepime for trigeminal neuralgia • NNT ~ 2.6 • NNH ~ 3.4

  30. Symptom control • Anticonvulsants • NNT for diabetic neuropathy (red) ~ 2.7 • NNT for post-herpetic neuralgia (white) ~ 3.2 • Collins J. Pain & Sym. Manag. 2000

  31. Symptom control • Anticonvulsants • Gabapentin • Less organ damage • No drug interaction

  32. Want to have a break?

  33. Symptom control • Intervention • Nerve / joint block • Counter-stimulation

  34. Symptom control • Nerve block • Where to cut • How to cut • What is left behind

  35. Symptom control • Nerve block • Where to cut • How to cut • What is left behind

  36. Symptom control • Nerve block • Where to cut • How to cut • What is left behind

  37. Symptom control • Nerve block • Where to cut • How to cut • What is left behind

  38. Symptom control • CNS nerve block • Physically protected, relatively immobile • Synapses are chemically vulnerable • Effects (and side effects) are wide spread

  39. Symptom control • Peripheral nerve block • Thick bundles of conducting cables • Mobile, difficulties with catheters • Impairment is profound yet localised

  40. Symptom control • Visceral nerve block • Contain visceral pain fibres k • Usually deep seated • Anatomically diffuse l • Visceral functions .

  41. Symptom control • Nerve block in chronic non-cancer pain • Preferably purely sensory block • Chemical / thermal neurolysis • Minimal dysfunction

  42. Symptom control • Nerve block in chronic cancer pain • Cover most abdominal viscera • 90% good to excellent relief • Eisenberg et al A&A 1995

  43. Symptom control • Joint block

  44. Symptom control • Joint block

  45. Symptom control • Transcutaneous Electrical Nerve Stimulation • (TENS) • Product of Gate theory • Better than placebo in short term • Minimal side effects • No long term benefit

  46. Symptom control • Spinal cord stimulation • Patient controlled • No medication • Permanent (almost)

  47. Symptom control • Spinal cord stimulation

  48. Symptom control • Spinal cord stimulation • Failed back surgery • Isolated neuropathy • Ischemic heart disease • Peripheral vascular disease • Pain relief as a therapy

  49. Symptom control • Spinal cord stimulation • de Jongste et al Br Heart J 1994

  50. Symptom control • Spinal cord stimulation • How does it compare with the “golden standard”?

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