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Nonopioid Analgesics and Adjuvants

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Handbook of Epidural Anaesthesia and Analgesia. New York, NY: Grune & Stratton, Inc; 1985:90. ... In: Neural Blockade in Clinical Anesthesia and Management of Pain. ... – PowerPoint PPT presentation

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Title: Nonopioid Analgesics and Adjuvants


1
Interventional Approachesto Chronic
PainBlocks, Stimulators, Pumps
2
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

3
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

4
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)

5
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

6
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

7
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

8
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.
9
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.
10
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)

11
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

12
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

13
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)

14
Trans-Ligamental Injection
Reproduced with permission from Covino BG, Scott
DB. Handbook of Epidural Anaesthesia and
Analgesia. New York, NY Grune Stratton, Inc
198590.
15
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.
16
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

17
Layering of Contrast in Epidural Space (C5-6
Epidural)
18
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

19
C 3-4 Facet Injection (Lateral View)
20
S1 Root Block (Trans-Sacral)
21
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

22
Lumbar Sympathetic Block (Lateral View)
23
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

24
Celiac Block (Lateral View)
25
CT-Guided Celiac Block
26
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)

27
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

28
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

29
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

30
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.
31
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.
32
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

33
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?

34
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.
35
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

36
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

37
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)

38
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

39
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