CHRONIC PAIN
AGNES CARUNGCONG MD
DEPARTMENT OF ANESTHESIOLOGY
OSPITAL NG MAYNILA MEDICAL CENTER
CHRONIC PAIN
• Pain that continues a month or more beyond the usual
recovery period the usual recovery period for an injury or
illness or goes for months or years due to a chronic
condition
• may not be constant but disrupts daily life
• interfere with sleep, keeping the patient awake at night
ACUTE VS CHRONIC PAIN
Characteristic
Acute Pain
Chronic Pain
Cause
Generally known
Often unknown
Duration of pain
Short,
well-characterized
Persists after healing,
3 months
Treatment
approach
Resolution of
underlying cause,
usually self-limited
Underlying cause and pain
disorder; outcome is often
pain control, not cure
DOMAINS OF CHRONIC PAIN
Quality of Life
Physical functioning
Ability to perform
activities of daily
living
Work
Recreation
Psychological Morbidity
Depression
Anxiety, anger
Sleep disturbances
Loss of self-esteem
Social Consequences
Socioeconomic
• Marital/family
relations
Consequences
• Intimacy/sexual activity
• Disability
• Social isolation
• Lost workdays
• Healthcare costs
NOCICEPTIVE VS NEUROPATHIC PAIN
Nociceptive
Pain
Mixed Type
Caused by activity in
neural pathways in
response to potentially
tissue-damaging stimuli
Caused by a
combination of both
primary injury and
secondary effects
Neuropathic
Pain
Initiated or caused by
primary lesion or
dysfunction in the
nervous system
CRPS*
Postoperative
pain
Arthritis
Mechanical
low back pain
Sickle cell
crisis
Sports/exercise
injuries
*Complex regional pain syndrome
Postherpetic
neuralgia
Trigeminal
neuralgia
Neuropathic
low back pain
Central poststroke pain
Distal
polyneuropathy
(eg, diabetic, HIV)
DEFINITION OF TERMS
• Neuropathic pain: Paroxysmal and lancinating, has a
burning quality and is associated with hyperpathia
• Deafferentation pain: neuropathic pain associated
with loss of sensory input into the CNS
• Sympathetically mediated pain: sympathetic system
plays a major role
DEFINITION OF TERMS
• Neuralgia – an extreme painful condition consisting of
recurrent episodes of intense shooting or stabbing
pain along the course of the nerve
• Causalgia – recurrent episodes of severe burning pain
• Phantom limb pain – feelings of pain in a limb that is
no longer there and has no functioning nerves
CHRONIC PAIN SYNDROMES
• Somatic – low back pain, degenerative and inflammatory
arthritis, lumbosacral radiculopathy, failed back surgery,
vertebral compression fractures, bony metastases,
Myofascial pain syndrome
• Visceral – abdominal cancers, chronic pancreatitis
• Neuropathic – CRPS, Post herpetic neuralgia, Trigeminal
neuralgia, diabetic neuropathy, phantom limb pain,
spinal stenosis/sciatica, spinal metastasis
EVALUATION
EVALUATION OF CHRONIC PAIN
• Medical evaluation (History, PE etc)
• Onset, Provokes/Palliates, Quality, Radiation, Severity,
Time, Response to previous treatments (OPQRSTRx)
• Plain radiographs (X-ray)
• CT-Scan
• MRI
• Bone Scans
• Electromyography and Nerve Conduction Studies
EVALUATION OF CHRONIC PAIN
• Pain Scales: Numerical rating scale, Faces rating
scale, Visual analog scale, McGill pain questionnaire
EVALUATION OF CHRONIC PAIN
MANAGEMENT
PAIN TREATMENT CONTINUUM
Least
invasive
Most
invasive
Psychological/physical approaches
Topical medications
Systemic medications*
Interventional techniques*
Continuum not related to efficacy
*Consider referral if previous treatments were unsuccessful.
MANAGEMENT
NON PHARMACOLOGIC TREATMENT
NONPHARMACOLOGIC OPTIONS
• Biofeedback
• Relaxation therapy
• Physical and occupational therapy
• Cognitive/behavioral strategies
• meditation; guided imagery
• Acupuncture
• Transcutaneous electrical nerve stimulation
MANAGEMENT
PHARMACOLOGIC TREATMENT
PHARMACOLOGIC TREATMENT OPTIONS
• Classes of agents with efficacy demonstrated
in multiple, randomized, controlled trials for neuropathic pain
• topical analgesics (capsaicin, lidocaine patch 5%)
• anticonvulsants (gabapentin, lamotrigine, pregabalin)
• antidepressants (nortriptyline, desipramine)
• opioids (oxycodone, tramadol)
• Consider safety and tolerability when initiating treatment
NONSTEROIDAL ANTI-INFLAMMATORY DRUGS
• Traditional NSAIDs are effective in the treatment of mild to
moderate pain, but their use is limited by potentially serious
adverse effects
• Ketorolac: indicated only in the management of moderately
severe acute pain that requires opioid level analgesics; no more
than 5 days
• COX-2 selective inhibitors (celecoxib, rofecoxib etc)
OPIOIDS: MORPHINE
• Morphine is the standard for opioid therapy for cancer pain.
• Metabolites: Morphine-6-glucuronide and Morphine-3glucuronide
• Dosing: 0.01-0.2mg/kg IV
OPIOIDS: MORPHINE
• Oral equinalgesic doses of morphine 10mg IV or
30mg per orem:
• 200mg codeine
• 30mg hydrocodone
• 20-30mg oxycodone
• 130mg propoxyphene
• 120mg tramadol
OPIOIDS: HYDROMORPHONE
• μ- receptor agonist
• 3-5x more potent > morphine (orally)
• 5-7x more potent (parenterally)
• Side effects are less frequent compared with morphine
• Metabolite: hydromorphone-3-glucoronide
OPIOIDS: METHADONE
• Has high potency and longer duration of action
• Has no metabolites
• Has additional salutary effects: NMDA receptor antagonist
and Serotonin reuptake inhibitor.
• Potency compared with morphine – 1:1 to 1:4, may be as
low as 1:10 with chronic usage
OPIOIDS: METHADONE
• Has unpredictable half-life – increasing risk
of accumulation
• Causes cardiac rhythm abnormalities: QT
prolongation and Torsade de pointes
OPIOIDS: OXYCODONE
• More potent than morphine when given intravenously (10x)
• Has low histamine release
• Has extensive first-pass hepatic metabolism = ↓ bioavailability
(10%)
• Has greater lipid solubility
• Should not be taken with alcohol: ↑ plasma concentration as
much as 300%
OPIOIDS: BUPRENORPHINE
• Partial agonist at μ-receptor, a κ-antagonist, and a weak ϩagonist.
• Has rapid onset when given orally (30 minutes)
• Long duration of action (6-9 hours)
• (+) abuse of drug
OPIOIDS: TRAMADOL
• Opioid agonist
• Bioavailability of 80-90%
• Low abuse potential
• Low incidence of constipation and minimal risk for fatal
respiratory depression
• Maximum dose is: 400-500mg/day
CO-ANALGESICS
• Agents which enhance analgesic efficacy, have independent
analgesic activity for specific types of pain, and/or relieve
concurrent symptoms which exacerbate pain
CO-ANALGESICS
• Antidepressants
• Anticonvulsants
• Corticosteroids
• Neuroleptics
• Antihistamines
• Benzodiazepines
• Antispasmodics
• Muscle relaxants
• Systemic local
anesthetics
ANTIDEPRESSANTS
• Effective agents in the treatment of neuropathic pain
• MOA: blockade of presynaptic reuptake of serotonin,
norepinephrine or both
• Side effects: anticholinergic effects (dry mouth, confusion,
urinary retention)
• E.g. Amitryptiline, Clomipramine, Doxepine, Fluoxetine,
Imipramine
ANTIDEPRESSANTS
ANTICONVULSANTS
• Blocks voltage-gated sodium channels and can suppress
spontaneous neuronal discharges
• Phenytoin, carbamazepine and valproic acid
• Gabapentin appears to be the most effective and well
tolerated at present.
LOCAL ANESTHETICS
• Lidocaine Infusion
• More effective in neuropathic pain but can be used for all
pain syndromes. Starting dose 0.5mg – 2mg/kg per hour IV
or SC. Some studies demonstrate long-lasting pain relief
even after drugs has been stopped. No need to decrease
opioids when starting
• Lidocaine Patch (700mg/adhesive)
• Maximum of 3 patches for 12/hr/day
PHARMACOLOGIC AGENTS
AFFECT PAIN DIFFERENTLY
BRAIN
CNS
PNS
Peripheral
Sensitization
Descending Modulation
Spinal
Cord
Dorsal
Horn
Local Anesthetics
Topical Analgesics
Anticonvulsants
Tricyclic Antidepressants
Opioids
Anticonvulsants
Opioids
Tricyclic/SNRI
Antidepressants
Central Sensitization
Anticonvulsants
Opioids
NMDA-Receptor Antagonists
Tricyclic/SNRI
Antidepressants
MECHANISTIC APPROACH TO PAIN THERAPY
Increase
Inhibition
TCA’s, SSRI’s,
Clonidine
Modify Expression
Anxiolytics
Decrease
Inflammatory
Response
NSAIDs,
Local Anesthetics,
Steroids
Decrease Conduction
Gabapentin,
Carbamazepine,
Local Anesthetics,
Opioids
Prevent
Centralization
COX 2,
Opioids,
Ketamine,
-2 Agonists.
WORLD HEALTH ORGANIZATION (WHO)
ANALGESIC LADDER.
DISTINGUISHING DEPENDENCE, TOLERANCE, AND
ADDICTION
• Physical dependence: withdrawal syndrome arises
if drug discontinued, dose substantially reduced,
or antagonist administered
• Tolerance: greater amount of drug needed to maintain therapeutic effect, or
loss of effect over time
• Pseudoaddiction: behavior suggestive of addiction; caused by undertreatment
of pain
• Addiction (psychological dependence): psychiatric disorder characterized by
continued compulsive use of substance despite harm
MANAGEMENT
INVASIVE PAIN TREATMENT
INTERVENTIONAL PAIN MANAGEMENT
• Epidural or Perineural injections of local anesthetics or cortico steroids.
• Implantations of epidural and intrathecal drug delivery systems.
• Neural ablative procedures.
• Insertion of spinal cord stimulators.
• Sympathetic nerve blocks.
ROLE OF INVASIVE PROCEDURES
• Intractable pain
• Intractable side effects
• Symptoms that persists despite carefully individualized patient
management
SELECTION OF BLOCK
• Depends on:
• Location of pain
• Presumed mechanism
• Skills of treating physician
• Local anesthetics can be applied locally, at peripheral nerve,
somatic plexus, sympathetic ganglia or nerve root, centrally in
neuraxis
SOMATIC NERVE BLOCKS
• Trigeminal nerve blocks
• Cervical, Thoracic, Lumbar paravertebral blocks
• Facet blocks
• Trans sacral nerve blocks etc.
LOW BACK PAIN: FACET SYNDROME
LOW BACK PAIN: FACET SYNDROME
SYMPATHETIC BLOCKS
• Stellate ganglion block
• Celiac plexus block
• Thoracic, lumbar sympathetic chain block etc.
EPIDURAL INJECTIONS
• Lumbar interlaminar epidural injections
• Fluoroscopic Injections
• Transforaminal injections
• Radiofrequency rhizotomy
LOW BACK PAIN AND RADICULAR PAIN SECONDARY TO
A HERNIATED DISC
LOW BACK PAIN AND RADICULAR PAIN SECONDARY TO
A HERNIATED DISC
• Steroids recommended for ESI:
• Methylprednisolone (largest)
• Betamethasone
• Triamcinolone (smallest)
• Dexamethasone (no identifiable particles)
PAIN TREATMENT CONTINUUM
Diagnosis
Oral Medications
PT, Exercise, Rehabilitation
Behavioral Medicine
Corrective Surgery
Therapeutic Nerve Blocks
Oral Opiates
Implantable Pain Management Devices
Neurostimulation
Intrathecal Pumps
Neuroablation
PRINCIPLES OF MANAGEMENT OF CHRONIC PAIN
• By the Mouth - Simple, effective, convenient
• By the Clock - Prevent pain after treating it
Do not use PRN. Do not wait for pain to return
• By the Ladder - move on to stronger analgesics if pain is
not controlled.
• Individualize
PAIN CONSULTATION TEAM
• Multidisciplinary group
• Provides consultation services only
•
not ongoing treatment
Consultation Team
Anesthesiology Neurology
Psychology
Pharmacy
Nursing
Referral
Recommendation
CHRONIC PAIN DISCIPLINES AND ROLES (CORE)
Anesthesiology – nerve blocks, pharmacologic
Kinesiotherapy – pool therapy; activity
Neurology – eval. treatment
Nursing – patient care
Physical Medicine/ Physical Therapy – exercise;
modalities
Psychology – eval. and treatment
Occupational Therapy – UE eval and treatment
Vocational Rehab – job eval and training
SUMMARY
• Chronic neuropathic pain is a disease, not a symptom
• “Rational” polypharmacy is often necessary
• combining peripheral and central nervous system agents enhances pain relief
• Treatment goals include:
• balancing efficacy, safety, and tolerability
• reducing baseline pain and pain exacerbations
• improving function and QOL
• New agents and new uses for existing agents offer additional treatment
options
REFERENCES
• Review Neuropathic pain: a practical guide for the clinician ; Ian Gilron, C.
Peter N. Watson, Catherine M. Cahill and Dwight E. Moulin
• Dworkin RH, Backonja M, Rowbotham MC, et al. Advances in neuropathic
pain. Arch Neurol 2003;60:1524-34.
• Gilron I, Bailey JM, Tu D, et al. Morphine, gabapentin, or their combination for
neuropathic pain. N Engl J Med 2005;352:1324-34.
• Stephen Macres, Understanding Neuropathic Pain
• Eisenberg E, McNicol ED, Carr DB. Efficacy and safety of opioid agonists in the
treatment of neuropathic pain of nonmalignant origin. JAMA 2005;293:304352.
Thank You!
DISTINGUISHING DEPENDENCE, TOLERANCE, AND
ADDICTION
• Physical dependence: withdrawal syndrome arises
if drug discontinued, dose substantially reduced,
or antagonist administered
• Tolerance: greater amount of drug needed to maintain therapeutic effect, or
loss of effect over time
• Pseudoaddiction: behavior suggestive of addiction; caused by undertreatment
of pain
• Addiction (psychological dependence): psychiatric disorder characterized by
continued compulsive use of substance despite harm