PAIN Acute pain Definition Measurement of Pain Pain pathway
Gate control theory Management of acute Pain
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PAIN Chronic pain Types: Nocieceptive Neuropathic
Pathophysiology Assessment of Chronic Pain Management of Chronic
Pain What is useful for exam
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Definition of pain An unpleasant sensory and emotional
experience associated with actual or potential tissue damage, or
described in terms of such damage International Association for the
Study of Pain
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Assessment An objective estimate of a subjective perception
(i.e. its difficult!) Clouded by personality and culture Scales
Pictures for children Numerical for adults
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Pain Pathways
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Gate control theory
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BEFORE PAIN!!
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POSTOPERATIVE PAIN Why bother? CVS Tachycardia Hypertension
Increased myocardial O 2 demand GI Nausea and vomiting Ileus RS
Vital Capacity FRC Basal atelectasis Respiratory infection Other
Urinary retention DVT + PE 2/3/2010PAIN16
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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 3 rd 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 Pathophysiology Chronic pain is not prolonged
acute pain
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Chronic Pain-central mechanisms
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Chronic Pain Pathophysiology is different from acute pain
Sensitization Reduced pain threshold (hyperalgesia) Non-painful
stimulus (allodynia)
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Chronic Pain Pathophysiology is different from acute pain
Nociceptive Pain Neuropathic pain Site Character Timing
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Chronic Pain Often neuropathic in origin 2 characteristic types
of pain Sharp, shooting Burning Examples Nerve root compression,
pancreatitis, ischaemic pain Pain experienced beyond area of
original injury (neural plasticity)
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ASSESSMENT OF CHRONIC PAIN HISTORY Site Nature Character
Alleviating and exacerbating factors PHYSICAL Examination MSK Limb
Back Neck Visceral PSYCHOSOCIAL Sensation of Pain Subjective
experience of Pain Attitudes and Beliefs Suffering and Distress
Illness Behaviour
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Case 1 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 1 A man with fracture forearm, compartment syndrome What
else do you noticed?
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Case 1 A man with fracture forearm, compartment syndrome He
wants to chop his forearm off. Useful?
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Case 2 A lady with difficulty in dressing Diagnosis?
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Case 2 A lady with difficulty in dressing Does topical therapy
help? Do NSAIDs help? Do Opioids help?
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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 she cannot sleep, eat and
became irritable Affect
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Ms. Unhappy She cannot work, go out, 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 3 Multi-faceted 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
Treatment implications? Pain-free Nociception or neuropathy
Normal activity & mood restored (e.g. Bogduk N. Management of
chronic low back pain. Med J Aust 2004; 180 (2): 79-83)
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Traditional Pain Treatment Ladder Physical Therapy (TENS)
Physical Therapy (TENS) Implantable Therapy (Intrathecal Pump)
Implantable Therapy (Intrathecal Pump) Implantable Therapy (Spinal
Cord Stimulator) Implantable Therapy (Spinal Cord Stimulator) Long
Term Oral Narcotics Meditation and Relaxation Behavioural Programs
Cognitive & Behavioural Therapies Behavioural Programs
Cognitive & Behavioural Therapies Nerve Blocks Neuro Ablation
NSAIDs (& over the counter drugs) NSAIDs (& over the
counter drugs) Krames E.S J Pain Symptom Manage; 1996: 333 - 352
Basic rule: failure of earlier treatments leads to consideration of
next in ladder
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Traditional Pain Treatment Ladder Physical Therapy (TENS)
Physical Therapy (TENS) Implantable Therapy (Intrathecal Pump)
Implantable Therapy (Intrathecal Pump) Implantable Therapy (Spinal
Cord Stim) Implantable Therapy (Spinal Cord Stim) Long Term Oral
Narcotics Meditation and Relaxation Behavioural Programs Cognitive
& Behavioural Therapies Behavioural Programs Cognitive &
Behavioural Therapies Nerve Blocks Neuro Ablation NSAID s (&
OTC drugs) NSAID s (& OTC drugs) Krames E.S J Pain Symptom
Manage; 1996: 333 - 352 Suggests that failure of earlier treatments
is indication for next in line.
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PAIN PERSISTING PHYSICAL DETERIORATION (eg. muscle wasting,
joint stiffness) FEELINGS OF DEPRESSION, HELPLESSNESS,
IRRITABILITY, SLEEP LOSS SIDE EFFECTS (eg. stomach problems
lethargy, constipation) M K Nicholas PhD Pain Management &
Research Centre Royal North Shore Hospital St Leonards NSW 2065
AUSTRALIA EXCESSIVE SUFFERING & DISABILITY Better to assess the
whole situation and plan treatment from there A BIOPSYCHOSOCIAL
PERSPECTIVE Influence of workplace, home, treatment providers
WORKPLACE, FINANCIAL DIFFICULTIES, FAMILY STRESS LONG-TERM USE OF
ANALGESIC, SEDATIVE DRUGS REPEATED TREATMENT FAILURES UNHELPFUL
BELIEFS & THOUGHTS REDUCED ACTIVITY
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Some conclusions Chronic pain is common (1 in 5 people) It is a
risk factor for disability The presence of mental disorders
increases risk of disability in those with chronic pain Curative
treatment is unlikely (no magic bullet) Interventions need to be
targeted against identified risk factors (bio psycho social)
Challenge: Collaborative approach offers best chance of success All
stakeholders must play active, informed roles
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Opioids Describe the classification of opioid receptors. Draw
the structure of morphine. Compare the characteristics of morphine,
fentanyl, alfentanil and pethidine What are the 2 main potentially
serious side effects of opioids? What are the main routes of giving
opioids? Discuss the advantages and disadvantages of each route. Is
morphine more or less efficacious in neonates compared with older
children? Does that mean you need more or less of it?
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Opioids induced hyperalgesia Desensitization of antinociceptive
mechanisms(Tolerance) Sensitization of pronociceptive mechanisms
Abnormal activation of NMDA receptors in CNS Long-term potentiation
of synapses between nociceptive C fibres and neurons in the spinal
cord horn.
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NSAIDS Discuss the uses, presentation and mode of action of
non-steroidal anti-inflammatory drugs (NSAIDs). What is the
difference between COX-1 and COX-2 inhibition, and the respective
side-effects? Discuss prostaglandins, thromboxanes, prostacyclin
and leukotrienes. In what situations should you be cautious about
using NSAIDs? By what routes may NSAIDs be given?
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Paracetamol How does paracetamol work? By what routes may
paracetamol be given? What is the oral loading dose of paracetamol?
Paracetamol may be used to treat: a. mild pain? b. moderate pain?
c. severe pain? How does paracetamol cause liver toxicity?
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ORAL ANALGESIA Paracetamol Side-effects extremely rare unless
taken in overdose 1% is metabolised to toxic metabolite and
normally inactivated by conjugation In overdose glutathione groups
depleted Excess metabolite binds to SH groups on liver
macromolecules hepatic necrosis R x N-acetylcysteine (-SH donor)
2/3/2010PAIN47
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Paracetamol Inhibits prostaglandin production Central action
?COX 3 not active in humans(cox,canabinoids,TPRV1,5HT3) Dose =
10-20mg/kg up to 1g Repeat 4 times a day (max 4g/day) Good opioid
sparing effect if given regularly Good antipyretic Poor
anti-inflammatory 2/3/2010PAIN48
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Misc Name the 4 main classes of analgesic drugs. What are
adjuvant analgesics? What is the mechanism of action of TENS? What
are the benefits of PCA?