Chronic Pain

							   Chronic Pain

        Dr. MC Chu
Anaesthesia and Intensive Care
            PWH
            Agenda
          Start at acute pain
Un-veil the complexity of chronic pain




In second part we will try to treat them
Let’s start with acute pain
             Tissue damage
      Site and intensity correlation
  Gets better with healing (self limiting)
          Case 1
A man with a pain in his right leg




“Are you sure it is the right leg?”
          Case 1
A man with a pain in his right leg




     How does it feel like?
          Case 1
A man with a pain in his right leg




 And any other abnormalities?
          Case 1
A man with a pain in his right leg




        What causes it?
Remarks from Case 1
Chronic pain is not prolonged acute pain
  Remarks from Case 1
Pathophysiology is different from acute pain

               Sensitization

   Reduced pain threshold (hyperalgesia)
      Non-painful stimulus (allodynia)
  Remarks from Case 1
Pathophysiology is different from acute pain

             Neuropathic pain

                   Site
                 Character
                  Timing

             More than that…
                  Case 2
A man with fracture forearm, compartment syndrome
         Fracture fixed, fasciotomy healed
             Neurovascular integrity OK
         But he has pain and other things
                  Case 2
A man with fracture forearm, compartment syndrome




            What else do you noticed?
                  Case 2
A man with fracture forearm, compartment syndrome




            What are the differentials?
                  Case 2
A man with fracture forearm, compartment syndrome




     He want to chop his forearm off. Useful?
 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…
          Case 3
A lady with difficulty in her dress




           Diagnosis?
          Case 3
A lady with difficulty in her dress




   Does physiotherapy help?
          Case 3
A lady with difficulty in her dress




  Does topical therapy help?
          Case 3
A lady with difficulty in her dress




       Does NSAID help?
          Case 3
A lady with difficulty in her dress




       Does opioids help?
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…
             King Mongkut
Lung cancer with pain in his chest, arm and abdomen
                   Case 4
Lung cancer with pain in his chest, arm and abdomen




          Why does he has a chest pain?
                   Case 4
Lung cancer with pain in his chest, arm and abdomen




          Why does he has an arm pain?
                   Case 4
Lung cancer with pain in his chest, arm and abdomen




       Why does he has an abdominal pain?
                   Case 4
Lung cancer with pain in his chest, arm and abdomen




              What bother him most?
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…
        Ms. Unhappy


Why can’t you fix my
neck and fxxk off
              Ms. Unhappy
        33 year old woman, traffic accident
                 “whiplash injury”
                MRI: unremarkable




Nociception
               Ms. Unhappy
 She felt so bad that he cannot sleep, cannot eat, and
                     became irritable




Affect
              Ms. Unhappy
She cannot work, cannot go out, cannot do housework,
                      cannot….




Social
                 Ms. Unhappy
She insisted to use a neck collar, visited 4 doctors for the
    “right diagnosis”, alcohol to “knock me off the pain”



Behavior
 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
Want to have a break?
     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: Bonica’s Management of Pain 3rd Ed.

“Pain without apparent biological value that persists beyond
    normal tissue healing (usually taken to be 3 months)”

                                        IASP 1986
Chronic pain as a disease
      Impact of chronic pain




                     Elliott et al Lancet 1999
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
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?
Chronic pain as a disease
       How much is this?




       Cost: 7 billion US$
Chronic pain as a disease
         How much is this?




     Cost: 4 million US$ per year
Chronic pain as a disease
      Impact of chronic pain




        White et al J. Occu. & Environ. Med. 2005
Clinical aspect
Scope of pain medicine
             Etiology

   Trauma (including iatrogenic)
    Cancer (and its treatment)
     Infections / inflammations
       Mechanical / functional
             Idiopathic
Scope of pain medicine
             Etiology

   Trauma (including iatrogenic)
    Cancer (and its treatment)
     Infections / inflammations
       Mechanical / functional
             Idiopathic
Scope of pain medicine
Complex Regional Pain Syndrome (CRPS)
 Type I and II (with obvious nerve injury)




         Which type is this one?
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
Scope of pain medicine
   Persistent post-operative pain




        Bay-Nielson Annals of Surgery 2001
  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
Scope of pain medicine
             Etiology

   Trauma (including iatrogenic)
    Cancer (and its treatment)
     Infections / inflammations
       Mechanical / functional
             Idiopathic
      Scope of pain medicine
                     Cancer pain

Over 50% cancer patients have severe pain at their end




    What contribute to this un-desirable outcome?
Scope of pain medicine
            Cancer pain

      Difficulties with treatment

    Side effects may be intolerable
            Oral intolerance
  Fatigue or impaired consciousness
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”
Scope of pain medicine
             Etiology

   Trauma (including iatrogenic)
    Cancer (and its treatment)
     Infections / inflammations
       Mechanical / functional
             Idiopathic
Scope of pain medicine
           Acute low back pain

    Leading cause for GP consultations
    Most (>90%) gets better in 2 weeks
Blind investigation yield is very low (< 5%)




       How many of you have this?
   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
Scope of pain medicine
            Acute low back pain

Most important: to exclude organic pathology
                “Red flags”
Scope of pain medicine
        Acute low back pain

        NSAID, paracetamol
  Avoid opioids / muscle relaxants
    Avoid aggressive physio
         Avoid bed rest

         Live a normal life
 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
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
Scope of pain medicine
        Chronic low back pain

 We all pay if pain allowed to progress
   Scope of pain medicine
              Chronic low back pain

          Structures potentially involved
Bone, disc, facet joints, ligaments, muscle, nerves




                How can we tell?
 Scope of pain medicine
           Chronic low back pain

Musculoskeletal Examination    k value

      Tenderness               0.24
      Muscle spasm             < 0.2



                         Deyo JAMA 1992
 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
       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 surgeon’s
                         suspicion.

                                  Waddell 1980
    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
Scope of pain medicine
         Chronic low back pain

 Mis-interpretation of non-organic signs

              Malingering
            Secondary gain
           Exclude pathology
            False positives
Scope of pain medicine
        Chronic low back pain

             Investigations
 Poor correlation with imaging findings




            This is obvious
Scope of pain medicine
        Chronic low back pain

             Investigations
 Poor correlation with imaging findings




          This is less obvious
Scope of pain medicine
       Chronic low back pain

          Investigations
   Diagnostic nerve / joint blocks




           Under-utilized
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?
Scope of pain medicine
        Chronic low back pain

 Failed back surgery syndrome (FBSS)




       More MRI, more surgery
            Therefore…
Scope of pain medicine
        Chronic low back pain

 Failed back surgery syndrome (FBSS)




                      Fritsch Spine 1996
                 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 I’m still here”
       You are consulted: “for better analgesics”
     Try this one
37 year old kindergarten teacher




 How would you assess her?
Any “better analgesic” to offer?
We will split the onion next time