RAJESH MENON 04/09/2013. PAIN Acute pain Definition Measurement of Pain Pain pathway Gate control...

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PAIN!! RAJESH MENON 04/09/2013

Transcript of RAJESH MENON 04/09/2013. PAIN Acute pain Definition Measurement of Pain Pain pathway Gate control...

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  • RAJESH MENON 04/09/2013
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  • 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
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  • Management MULTIMODAL THERAPY PHARMACOLOGICAL ANALGESICS ADJUVANTS INTERVENTIONS NONPHARMACOLOGICAL TENS PHYSIOTHERAPY OCCUPATIONAL THERAPY ACUPUNTURE COGNITIVE BEHAVIOYRAL THERAPY SELF MANAGEMENT PROGRAMME EDUCATION COPING STRATEGIES RELAXATION TECHNIQUE EXCERCISE( GRADED) PHASING
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  • 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?
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  • QUESTIONS