Nonopioid Analgesics and Adjuvants

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Interventional Approachesto Chronic
PainBlocks, Stimulators, Pumps
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Background

• Neurosurgical ablative treatments for pain since
  19th century but now infrequently used
• Ablation eclipsed by percutaneous injections or
  therapies that target central or peripheral
  pathways
• Nerve blocks
• Spinal stimulation
• Pumps

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Nerve Blocks (I)

• Diagnostic local anesthetic only, to clarify
  mechanism or simulate effects of therapy
• Therapeutic anesthetize a site or pathway
  temporarily (local anesthetic) or permanently
  (lytic agent), or reduce inflammation
  (corticosteroid)
• A block may be both diagnostic and therapeutic,
  eg, sympathetic block or trigger-point injection

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Nerve Blocks (II)

• Common blocks for chronic pain include
• Trigger-point injection
• Tourniquet or Bier block
• Peripheral nerve injection (eg, ilioinguinal,
  lateral femoral cutaneous, greater occipital)
• Paravertebral (nerve root) injection
• Epidural injection
• Intra-articular (eg, facet, SI) injection
• Sympathetic block (cervical, lumbar)
• Plexus block (celiac, hypogastric)

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Nerve Blocks (III)

• Case reports, preclinical data support
  long-lasting effects of local anesthetic blockade
• RCTs support lytic celiac block
• However, unclear how much clinical improvement
  reflects placebo effects, irrelevant cues,
  systemic absorption of local anesthetic,
  expectations
• Side effects possible
• Rarely successful as a stand-alone strategy for
  chronic pain

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Trigger-Point Injection I

• Essential criteria
• Taut band palpable (if muscle accessible)
• Exquisite spot tenderness of a nodule in a taut
  band
• Pressure on tender nodule reproduces pain
• Range of motion with stretch limited by pain
• Confirmatory observations
• Visual or tactile identification of local twitch
  response
• Local twitch response on needling tender nodule
• Pain/hyperesthesia in recognized pattern
• Activity in tender nodule on EMG

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Trigger-Point Injection II

• Trigger points may refer pain
• Toward the periphery (eg, suboccipital,
  infraspinatus)
• Proximally or medially (eg, biceps brachii)
• Locally (eg, serratus posterior inferior)
• Techniques
• Needle only (no injection)
• Local anesthetic only
• Local anesthetic glucocorticoid (evidence?)
• Botulinum toxin type A

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Trigger-Point Injection III
Reproduced with permission from Simons DG, et al.
Travell Simons Myofascial Pain and
Dysfunction The Trigger Point Manual. Vol. 1.
2nd ed. Philadelphia, Pa Williams Wilkins
1999160.
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Trigger-Point Injection III
Reproduced with permission from Simons DG, et al.
Travell Simons Myofascial Pain and
Dysfunction The Trigger Point Manual. Vol. 1.
2nd ed. Philadelphia, Pa Williams Wilkins
1999159.
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Tourniquet or Bier Block

• Facilitates mobilization of upper or lower
  extremity in known or suspected CRPS
• Same technique for sympathetically-maintained
  versus sympathetic-independent pain
• Many variants all use IV cannulation, drainage
  of blood (gravity, Esmarchs bandage), proximal
  tourniquet (eg, systolic BP 100), slow release
  after 20 min
• Medications local anesthetic, many others
  (sympatholytic, anti-inflammatory)

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Peripheral Nerve Injection

• Spontaneous entrapment syndromes
• Greater occipital (occipital neuralgia)
• Lateral femoral cutaneous (meralgia paresthetica)
• Ilioinguinal
• Post-incisional or post-traumatic neuroma
• Cranial (post-craniotomy)
• Intercostal (post-thoracotomy)
• Abdominal wall (trochar sites)
• Herniorrhaphy
• Local anesthetic glucocorticoid

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Paravertebral (Nerve Root) Injection

• Diagnostic
• Establish or confirm anatomic mechanism of pain
  (eg, atypical dermatomal distribution in disk
  disease or multilevel foraminal stenosis)
• Therapeutic
• Deposit local anesthetic plus glucocorticoid via
  paravertebral and/or transforaminal approach
• Technique
• Fluoroscopy or CT essential to validate, document
  needle placement
• Radiopaque contrast outlines/tracks root

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Epidural Injection (I)

• Employed for decades using various techniques,
  materials, and patients
• Poor documentation of diagnosis, pain, technique,
  outcomes
• Limited RCT evidence of efficacy in
  subpopulations, but most reports are case series
• Techniques (glucocorticoid local anesthesic)
• Translaminar
• Transforaminal
• Caudal (useful if prior lumbar surgery, scarring)

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Trans-Ligamental Injection
Reproduced with permission from Covino BG, Scott
DB. Handbook of Epidural Anaesthesia and
Analgesia. New York, NY Grune Stratton, Inc
198590.
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Sacral Extradural Injection
Reproduced with permission from Eriksson E, ed.
Illustrated Handbook in Local Anaesthesia. 2nd
ed. London, Eng Lloyd-Luke (Medical Books) Ltd
1979135.
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Epidural Injection (II)

• Applied for symptomatic relief in
• Disk protrusion with radiculopathy
• Spinal stenosis (circumferential or foraminal)
• Acute pain, local inflammation of vertebral
  fracture (? subsequent vertebroplasty)
• ? Acute herpes zoster, using local anesthetic
  alone
• May facilitate rehabilitation, avert surgery when
  applied within multidisciplinary framework

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Layering of Contrast in Epidural Space (C5-6
Epidural)
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Intra-Articular Injection

• Facet, large joints, sacroiliac most common
• Diagnostic
• Clarify clinical impression of a facet syndrome
  or SI joint pain
• (Facet) simulate results of potential spinal
  fusion or denervation of medial branch of dorsal
  ramus
• Therapeutic (local anesthetic glucocorticoid)
• Reduce inflammation, pain
• Increase mobility, facilitate rehabilitation
• Controversy as to efficacy and effectiveness

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C 3-4 Facet Injection (Lateral View)
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S1 Root Block (Trans-Sacral)
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Sympathetic Block

• Diagnostic
• Superior cervical (stellate) ganglion
• Lumbar
• Note need for (but insurers reluctance to pay
  for) placebo controls
• Therapeutic
• CRPS of upper, lower extremity
• Facial neuralgias
• Technique
• Local anesthetic
• Neurolytic

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Lumbar Sympathetic Block (Lateral View)
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Plexus Block (Celiac, Hypogastric)

• Visceral nociceptive afferent pathways are
  heterogeneous sympathetic (eg, celiac),
  parasympathetic (eg, hypogastric)
• Meta-analysis indicates efficacy of celiac block
  for abdominal cancer pain, but case series show
  little benefit (lt10) in chronic pancreatitis
• Case series of hypogastric block for perineal
  pain
• Technique
• Fluoroscopy or CT essential for safety,
  documentation
• Reversible block with local anesthetic
• Neurolysis with alcohol, phenol

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Celiac Block (Lateral View)
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CT-Guided Celiac Block
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Spinal Cord Stimulation

• Background peripheral electrical stimulation for
  pain control since prehistory recent gate
  theory
• Retrospective, uncontrolled case series show that
  SCS can reduce intensity of neuropathic pain
• Biases in existing literature (lack of blinding,
  heterogeneity of interventions/assessments, small
  numbers) confound its interpretation
• Recent 6-month RCT with careful selection of
  patients and successful test stimulation, SCS is
  safe, reduces pain and improves HRQOL in chronic
  RSD (Kemler MA, et al. N Engl J Med. 2000 N
  36)

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Possible Risks (SCS or Pump)

• Non-specific electrical, mechanical (migration,
  separation of electrode or catheter) failure
• Route-specific infection, fibrosis, extrusion
• Drug-specific (pump) neurotoxicity, sedation,
  constipation, hypotension
• For opioids (pump) constipation, urinary
  retention, nausea, impotence, nightmares,
  pruritus, edema, sweating, fatigue

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Implanted Pumps for Pain

• Spinal anesthesia 100 y
• Selective spinal opioid analgesia 25 y
• Early chronic use of opioid PCEA supplanted by
  intrathecal cannulation
• Single agents opioids, local anesthetics,
  NSAIDs, clonidine, cholinomimetics, calcium
  channel blockers, GABA-A and -B, peptides, NMDA
  antagonists, adenosine
• Combinations opioid-opioid, opioid-local
  anesthetic, morphine-clonidine

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Theoretical Benefits of IT Rx (I)

• Targeting offers dosage reductions
• Only route possible for certain drugs
• Fewer side effects from decreased and spatially
  restricted dosage
• Greater efficacy from targeted, higher
  concentrations (eg, in neuropathic pain) and
  locally applied combinations

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Theoretical Benefits of IT Rx (II)

• Nociceptive activity provokes persistent
  functional and morphologic changes
• Pain, especially chronic pain, is a disease
• Spinal analgesic therapy dorsal horn amnesia
• Combination analgesic chemotherapy

See Carr DB, Cousins MJ. Spinal route of
analgesia. Opioids and future options. In Neural
Blockade in Clinical Anesthesia and Management
of Pain. 3rd ed. Philadelphia, Pa
Lippincott-Raven 1998915-983.
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Algogenic Neuropoiesis

• Transformation of neuronal morphology and
  function as the result of nociception
• Poiesis organized creation, growth
• A highly organized process (Ca, second
  messengers, oxidative stress, novel gene
  expression, growth factors, apoptosis)

See Walker S, et al. Anesth Analg. In press.
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IT Analgesia Evidence

• Abundant preclinical proof of IT analgesia using
  various agents, singly or in combination
• Narrative reviews from 1980s1990s summarize
  clinical effectiveness and conclude IT analgesia
  generally is safe, well-tolerated, effective for
  acute or chronic cancer and noncancer pain

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IT Evidence Limitations (I)

• Level 5 clinical evidence (uncontrolled case
  reports/series)like gt90 of all pain literature
• Inclusion based upon failure of prior therapy but
  unclear whether/how therapy optimized
• Nonuniform or unknown Dx, pain/QOL scores
• Side effects vs effects different dimensions
• Limited psychologic, toxicologic data
• Effect of drug redistribution?

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IT Evidence Limitations (II)

• No controls UNDEFINABLE relative efficacy!
• Without data on relative efficacy,
  algorithms/guidelines follow practice-based
  evidence
• For evidence-based practice, RCTs or CCTs are
  necessary to control for expectations,
  psychosocial and placebo/nocebo effects
• Consort statement needed for pain trials
• Need for additional large published controlled
  studies highlighted by review of Bennett et al

See Bennett G, et al. J Pain Symptom Manage.
200020S37-S43.
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Intrathecal Opioids Prospects

• Opportunity for translational research on dorsal
  horn amnesia
• Need for uniformity, control groups
• Requirement for appropriately powered trials
  size does matter
• Control for drug interactions
• Long-term follow-up
• Clinical consensus drives initial opioid use
  alone, but may be better to start with
  combinations

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Prudent Practice

• Any nerve block, no matter how deftly and
  carefully performed, can lead to sudden
  complications related to intraneural,
  intraspinal, or intravascular injection
• Anyone who considers performing a nerve block
  should provide monitoring, vigilance during and
  afterwards, and resources for prompt resuscitation

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A Thought

• Interventional approaches often are reserved for
  patients with well-established problems, failure
  of other Rx, and pronounced disability
• Do we miss an opportunity for early,
  cost-effective preventive treatment by reserving
  interventions for those least likely to benefit?
• Established neuropoiesis, entrenched pain
  behavior, proven self-advocacy in disabled role
  may explain data on low likelihood of return to
  work
• Youth is a wonderful thing what a crime to
  waste it on children (George Bernard Shaw)

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Conclusions

• Best to reserve blocks, other invasive Rx for
  when other modalities fail?
• Substantial risks and benefits of SCS, IT Rx
• Stand-alone interventions less likely to succeed
  than multidisciplinary ones
• Irresistible force (evidence-based medicine) now
  is meeting immovable object (case reports,
  customary practice)
• Needed outcomes data on effectiveness and large
  RCTs re efficacy

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