Transcript Pain2010

PAIN
By Dr. Cuong Ngo-Minh
Back to Basics
April 14th 2010
Objectives
• To differentiate between Nociceptive from Neuropathic types of pain
on neural basis
• To make a differential diagnosis of causes of pain.
• To clinically assess pain and it’s impact on daily function by history
and search for most likely cause
• To create an individualized plan of management for patients with
acute or chronic pain. Use multiple modalities to relieve pain.
• Select clients appropriately for referral to pain specialist,
interdisciplinary approach.
Definitions 1
• PAIN: « an unpleasant sensory and emotional experience
associated with actual or potential tissue damage or described in
terms of such damage » by the International Association for the
Study of Pain.
• A) Nociceptive pain is cause by DIRECT stimulation of peripheral
nociceptors.
It is usually associated with TISSUE DAMAGE as well as
inflammation processes. Nociceptive pain is sub-categorized into
A1) somatic which can be superficial (skin) or deep pain (eg tumor
infiltration, arthritis)
A2) visceral (eg. Pancreatitis, Crohn’s disease).
Pathophysiology: SOMATIC pain signal start with the AFFERENT
MYELINATED A-delta fibers (sharp pain) then goes to the C fibers
(delayed dull pain). Visceral pain (eg endometriosis): the afferent
travel with sympathetic and parasympathetic fibers.
Definitions 2
• B) Neuropathic pain is caused by an injury to the peripheral or
central nervous system or is due to sensitazation of central pain
neurons.
B1) Sympathetic via maintained sympathetic Efferent activity
eg Complex regional pain syndrome type 1 – Reflex sympathetic
dystrophy Pain wildly out of proportion to soft tissue or bone injury
but no nerve injury. Nerve block may help.
- Type 2 causalgia where pain wildly out of proportion to nerve
injury (by EMG-NerveConductionStudy).
B2) Non-Sympathetic via damage to peripheral nerve (eg. Mechanical
herniated disc, Neuroma of Morton, Infectious: post-herpetic
neuralgia)
C) Central via Central nervous system Deafferation pain: no need
for peripheral stimulus eg. Post stroke, spinal cord injury, Phantom
Limb)
History for Pain 1
• Use systematic questionnaire to find the cause of pain.
A) Where : point to area(s), localized/generalized, radiating
B) When/frequency: Acute vs chronic (more than 6 weeks) Specific
triggering factor/acute event vs progressive.
C) Intensity: scale 1-10, Visual Scale/facial expression, mild-moderatesevere, Relieving and worsening factors
D) Type: constant vs intermittent , superficial vs deep, sharp/dull,
burning, electric shock
E) Context: Work-related, MVA accident, F) Functional impairement:
Work, Home, sleep, quality of life, FIFE =Feelings Ideas Function
Expectation-Emotions. Socio-economic support.
History for Pain 2
• Past Medical History: Cancer, Accident, Surgery, medical illness
(Diabetes, CVA, Neurological illness eg Multiple sclerosis,
neuropathy, Arthritis),
Mental illness (depression, anxiety,
somatization,...). Drug users and addiction history.
• List of medications prescribed (acetaminophen, Nsaids, narcotics,
co-analgesic (amitriptilline, neurontin, pre-gabelin,...), psychotropes
eg Effexor) and overcounter medications.
• Review of system to look for « red flags »
Systemic symptoms of
neurological symptoms
weight
loss,
diaphoresis,
asthenia,
Physical examination for Pain
Antalgic gait? Is pain intensity change with distraction? Reproductibiliy
of pain? (use of PROVOCATIVE manoeuvers is KEY)
• Facial expression, vitals signs
• Complete physical exam with more attention to painful structures,
according to clinical hypothesis coming from history and r/o sign of
cancer (localized or with metastasis), Range of motion, Trigger
points, guarding, rebound
• Muscolo- Neurological exam, ? Swelling ? Redness ? AllodyniaHyperesthesia
search for signs to decide if nociceptive vs neuropathic
• Mental status r/o sign of co-morbid mental illness
• « perform complete physical examination regardless of complain »
Investigations and management for pain 1
• Investigation are done to confirm or infirm hypothesis of diagnosis
(eg Imaging, MRI L-Spine for Low back pain)
eg If suspect cancer of pancreas : CT abdomen
For neuropathy: EMG-NCS
Refer to specialists appropriately to treat the cause of pain (eg
oncologist if cancer). For advise on pain relief for non-cancer pain,
refer to pain specialists (re: Chronic Pain Management clinic) who
can offer Injections (nerve blocks, epidural...) and interdisciplinary
team approach
Investigations and management for pain 2
• For pain symptom relief, use multimodal (non-pharmacologic and
pharmacologic) approach.
• Holistic approach, especially for total pain/ suffering.
• Experience of pain differs from individuals affected by same
disease/condition so treatment is in case by case basis. Even for
the same person, pain changes over time. Approach differs
depending if Acute vs Chronic, Cancer pain vs Non-cancer pain.
Investigations and management for pain 3
• Non-pharmacologic includes: physiotherapy-exercice, TENS, Adjustement of
work activities, Acuponcture, Massotherapy, psychotherapy, surgery ...
• Pharmacologic:1) Non- opioids: Acetaminophen, NSAIDS, steroids
Opiods (codeine, tramadol, morphine, oxycodone, hydromorphone, fentanyl,
methadone),
ADJUVANT Tricyclic (eg amitryptilline), Anticonvulsant as adjuvant therapy
(gabapentin, pregabelin, ...). Cannabinoids eg nabilone Always assess
Benefice vs Risk/side effects ratio.
• Use combination eg opioid long-acting,
PRN short acting opioid and
adjuvant (eg pre-gabelin). Treat comorbid conditions: eg. Antidepressant.
Use laxatives with narcotics.
Investigations and management for pain 4
• Narcotic use principles:
1) Try non-narcotic treatment first, up to their maximum dose tolerated
2) Goal is NOT pain= 0 but pain relief to allow Functional status in daily
activities
3) Progressive titration of dose of narcotic. Use minimal dose that relieve pain/
assure function. Titrate with short acting opiods eg hydromorphone. Once
stable dose (not frequent PRN), use total daily dose and convert to long
acting meds eg Hydromorphone Contin. Manage side effects: constipation,
nausea, confusion
4) Tolerance effect: Same dose not as efficient to relieve pain so need to
increase dose. Tolerance is different than addiction! « Explain that the
correct use of morphine is more likely to prolong a more rested, pain free
life »
5) Narcotics can be used for non-cancer pain: need narcotic contract to avoid
abuse.
Investigations and management for pain 4
• Third party issues: Employer, Worker’s Comp or WSIB, Private Insurance
and objective assessment of functional status.
• Quality of life eg Palliative care. Capacity issues in end-stage disease.
Caregiver stress.
Euthanasia and Physician assisted suicide are illegal in Canada.
No maximum dose, use necessary dose of narcotics to relieve pain (but
document reasoning and monitor) and assure quality of life. Counsel care
givers.
Summary for pain management
• History and physical to search for cause of pain. Management
differs from Acute vs Chronic pain,
Goal is to improve functional status.
Cancer vs Non-Cancer pain.
• Use multiple approach
non-pharmacologic and pharmacologic
modalities to relieve pain and co-morbid conditions (eg depression).
Set action plan with client and caregivers.
• Refer appropriately for diagnosis and management. Eg pain
specialist can do epidurals, nerve block or neurolysis
Consent, capacity, controversial ethical issues
(Cleo 4.3, 4.10)
• Capacity: ability to decide with understanding and appreciate consequence
(pro-cons) of decision. Capacity for health is different from financial
capacity
• Capacity is affected by factors: severity of physical and psychological illness,
effect of medications/ delirium, religious belief and values, fear of death.
• Issues of Euthanasia and Physician Assisted Suicide (illegal in Canada)
“ The candidate will be aware that they may be asked to comment on
unresolved or controversial ethical issues and will be able to name and
describe relevant key issues and ethical principles”
“Contrast resp. depression caused by opioids to resp rate 6-8bpm of dying
patient in which resp depression is not caused by opioids but a natural part
of dying process”. Titrate Rx to provide appropriate pain control.
Ressources
1) Managing pain. The Canadian Healthcare Professional’s Reference
by the Canadian Pain Society, Dr Jovey Editor
2) Practice Based Learning program from McMaster University, Module
on Chronic Non Cancer Pain, Vol 11(10), August 2003