Chronic Pain

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Chronic Pain

• Dr. MC Chu
• Anaesthesia and Intensive Care
• PWH

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Agenda

• Start at acute pain
• Un-veil the complexity of chronic pain
• In second part we will try to treat them

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Lets start with acute pain

• Tissue damage
• Site and intensity correlation
• Gets better with healing (self limiting)

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Case 1

• A man with a pain in his right leg
• Are you sure it is the right leg?

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Case 1

• A man with a pain in his right leg
• How does it feel like?

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Case 1

• A man with a pain in his right leg
• And any other abnormalities?

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Case 1

• A man with a pain in his right leg
• What causes it?

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Remarks from Case 1

• Chronic pain is not prolonged acute pain

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Remarks from Case 1

• Pathophysiology is different from acute pain
• Sensitization
• Reduced pain threshold (hyperalgesia)
• Non-painful stimulus (allodynia)

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Remarks from Case 1

• Pathophysiology is different from acute pain
• Neuropathic pain
• Site
• Character
• Timing
• More than that

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Case 2

• A man with fracture forearm, compartment syndrome
• Fracture fixed, fasciotomy healed
• Neurovascular integrity OK
• But he has pain and other things

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Case 2

• A man with fracture forearm, compartment syndrome
• What else do you noticed?

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Case 2

• A man with fracture forearm, compartment syndrome
• What are the differentials?

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Case 2

• A man with fracture forearm, compartment syndrome
• He want to chop his forearm off. Useful?

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Remarks from Case 2

• Impairment is different from acute pain
• Pain can come without obvious pathology
• Pain, motor, sudomotor or sensory changes
• Trophic changes
• Exclude differentials
• One more example

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Case 3

• A lady with difficulty in her dress
• Diagnosis?

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Case 3

• A lady with difficulty in her dress
• Does physiotherapy help?

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Case 3

• A lady with difficulty in her dress
• Does topical therapy help?

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Case 3

• A lady with difficulty in her dress
• Does NSAID help?

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Case 3

• A lady with difficulty in her dress
• Does opioids help?

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Remarks from Case 3

• Treatment are different from acute pain
• Partial response to common analgesics
• Long term side effects
• Tolerances, organ damages
• Not all chronic pains are neuropathies

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King Mongkut

• Lung cancer with pain in his chest, arm and
  abdomen

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Case 4

• Lung cancer with pain in his chest, arm and
  abdomen
• Why does he has a chest pain?

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Case 4

• Lung cancer with pain in his chest, arm and
  abdomen
• Why does he has an arm pain?

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Case 4

• Lung cancer with pain in his chest, arm and
  abdomen
• Why does he has an abdominal pain?

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Case 4

• Lung cancer with pain in his chest, arm and
  abdomen
• What bother him most?

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Remarks from Case 4

• Pain is common source of distress
• Multiple etiologies
• Iatrogenic
• Other somatic symptoms
• Other psychosocial factors
• Role of palliative medicine
• Now, the classical onion

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Ms. Unhappy
Why cant you fix my neck and fxxk off
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Ms. Unhappy

• 33 year old woman, traffic accident
• whiplash injury
• MRI unremarkable

Nociception
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Ms. Unhappy

• She felt so bad that he cannot sleep, cannot eat,
  and became irritable

Affect
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Ms. Unhappy

• She cannot work, cannot go out, cannot do
  housework, cannot.

Social
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Ms. Unhappy

• She insisted to use a neck collar, visited 4
  doctors for the right diagnosis, alcohol to
  knock me off the pain

Behavior
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Remarks from Case 5

• Multi-facet problems of chronic pain
• Nociception is different
• Mood is altered
• Behavior and thoughts are changed
• Function is impaired
• They are a different person altogether
• Chronic pain is a disease of its own
• Pain Management is a specialty of its own

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• Want to have a break?

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Chronic pain as a disease

• Definitions
• Pain extending for a long period of time,
  represents low levels of underlying pathology
  that does not explain the presence and extent of
  pain, or both
• Turk in Bonicas Management of Pain 3rd Ed.
• Pain without apparent biological value that
  persists beyond normal tissue healing (usually
  taken to be 3 months)
• IASP 1986

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Chronic pain as a disease

• Impact of chronic pain
• Elliott et al Lancet 1999

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Chronic pain as a disease

• Impact of chronic pain
• 10.8 of local adult Chinese
• 38 work affected
• 34 daily activities affected
• 30 on long term analgesics
• Ng et al Clin. J. Pain 2002

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Chronic pain as a disease

• Impact of chronic pain
• 38 Billion Euro per year in Germany
• 62 Billion US per year in US
• Zimmermann Orthopade 2004
• Steward et al JAMA 2003
• How much is this?

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Chronic pain as a disease

• How much is this?
• Cost 7 billion US

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Chronic pain as a disease

• How much is this?
• Cost 4 million US per year

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Chronic pain as a disease

• Impact of chronic pain

White et al J. Occu. Environ. Med. 2005
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• Clinical aspect

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Scope of pain medicine

• Etiology
• Trauma (including iatrogenic)
• Cancer (and its treatment)
• Infections / inflammations
• Mechanical / functional
• Idiopathic

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Scope of pain medicine

• Etiology
• Trauma (including iatrogenic)
• Cancer (and its treatment)
• Infections / inflammations
• Mechanical / functional
• Idiopathic

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Scope of pain medicine

• Complex Regional Pain Syndrome (CRPS)
• Type I and II (with obvious nerve injury)
• Which type is this one?

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Scope of pain medicine

• Complex Regional Pain Syndrome (CRPS)
• Pathophysiology is unknown
• Diagnosis is clinical
• Investigations are not diagnostic
• Treatment is empirical
• Prognosis 30 loss of work at 1 year
• early intervention to prevent disability
• Atkins J. Bone Joint Surg 2003

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Scope of pain medicine

• Persistent post-operative pain
• Bay-Nielson Annals of Surgery 2001

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Scope of pain medicine

• Persistent post-operative pain
• Predictive factor intensity of early post-op.
  pain
• Most will resolve slowly
• Is it preventable?
• Role of pre-emptive analgesia still uncertain
• Should be part of the surgical consent

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Scope of pain medicine

• Etiology
• Trauma (including iatrogenic)
• Cancer (and its treatment)
• Infections / inflammations
• Mechanical / functional
• Idiopathic

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Scope of pain medicine

• Cancer pain
• Over 50 cancer patients have severe pain at
  their end
• What contribute to this un-desirable outcome?

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Scope of pain medicine

• Cancer pain
• Difficulties with treatment
• Side effects may be intolerable
• Oral intolerance
• Fatigue or impaired consciousness

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Scope of pain medicine

• Cancer pain
• Difficulties with treatment
• Patients and doctors refuse treatment
• Denial of disease progression
• Hope of curing the incurable
• Myths of analgesics, including addiction
• Opio-phobia

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Scope of pain medicine

• Etiology
• Trauma (including iatrogenic)
• Cancer (and its treatment)
• Infections / inflammations
• Mechanical / functional
• Idiopathic

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Scope of pain medicine

• Acute low back pain
• Leading cause for GP consultations
• Most (gt90) gets better in 2 weeks
• Blind investigation yield is very low (lt 5)
• How many of you have this?

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Scope of pain medicine

• Acute low back pain
• Most important to exclude organic pathology
• Red flags
• Fever
• History of trauma
• Constitutional (weight / appetide loss)
• Neurological (cauda equina /radiculopathy)
• Non-spine pathology eg pulsatile abdominal mass

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Scope of pain medicine

• Acute low back pain
• Most important to exclude organic pathology
• Red flags

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Scope of pain medicine

• Acute low back pain
• NSAID, paracetamol
• Avoid opioids / muscle relaxants
• Avoid aggressive physio
• Avoid bed rest
• Live a normal life

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Scope of pain medicine

• Acute low back pain
• Predictive of chronicity and disability
• Yellow flag
• Fear avoidance behavior
• Negative belief that pain is harmful or disabling
• Excessive focusing on pain
• Expectation on passive pain management
• Linton Spine 2000

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Scope of pain medicine

• Acute low back pain
• Predictive of chronicity and disability
• Yellow flag
• Depressed mood, social withdrawal
• Co-existing financial and social problems
• Poor job satisfaction
• Linton Spine 2000

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Scope of pain medicine

• Chronic low back pain
• We all pay if pain allowed to progress

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Scope of pain medicine

• Chronic low back pain
• Structures potentially involved
• Bone, disc, facet joints, ligaments, muscle,
  nerves
• How can we tell?

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Scope of pain medicine

• Chronic low back pain
• Musculoskeletal Examination k value
• Tenderness 0.24
• Muscle spasm lt 0.2
• Deyo JAMA 1992

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Scope of pain medicine

• Chronic low back pain
• Neurological Examination k value
• Weak ankle dorsiflexion 1.0
• Normal ankle reflexes 0.39
• Straight leg raising 0.6
• Deyo JAMA 1992

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Scope of pain medicine

• Chronic low back pain
• Non-organic signs
• find ways of predicting surgical failure to
  treat back pain
• 8 physical signs associated with higher
  personality score abnormalities, multiple
  surgeries and surgeons suspicion.
• Waddell 1980

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Scope of pain medicine

• Chronic low back pain
• Non-organic signs
• Non-anatomical motor / sensory loss
• Superficial / non-anatomical tenderness
• Simulation (pelvic rotate, axial load,
  distraction SLR)
• Over-reaction
• 3 out of 8

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Scope of pain medicine

• Chronic low back pain
• Mis-interpretation of non-organic signs
• Malingering
• Secondary gain
• Exclude pathology
• False positives

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Scope of pain medicine

• Chronic low back pain
• Investigations
• Poor correlation with imaging findings
• This is obvious

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Scope of pain medicine

• Chronic low back pain
• Investigations
• Poor correlation with imaging findings
• This is less obvious

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Scope of pain medicine

• Chronic low back pain
• Investigations
• Diagnostic nerve / joint blocks
• Under-utilized

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Scope of pain medicine

• Chronic low back pain
• Surgery is indicated if
• Failed conservative treatment
• Demonstrable pathology
• Correlation with clinical findings
• Minimal psychosocial complications
• Why are we so cautious?

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Scope of pain medicine

• Chronic low back pain
• Failed back surgery syndrome (FBSS)
• More MRI, more surgery
• Therefore

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Scope of pain medicine

• Chronic low back pain
• Failed back surgery syndrome (FBSS)
• Fritsch Spine 1996

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Try this one

• 37 year old kindergarten teacher
• Sprained her back while lifting a child 2 years
  ago
• Seen GP and several Orthopediac surgeons
• Had a few spine X-rays and an MRI
• Bone spurs everywhere
• Scheduled for spinal fusion
• Patient next bed I have that 3 times, and Im
  still here
• You are consulted for better analgesics

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Try this one

• 37 year old kindergarten teacher
• How would you assess her?
• Any better analgesic to offer?

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• We will split the onion next time