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Interventional Approaches to Chronic Pain: Blocks, Stimulators, Pumps. 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

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Interventional Approaches to Chronic Pain: Blocks, Stimulators, Pumps

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Interventional approaches to chronic pain blocks stimulators pumps

Interventional Approachesto Chronic Pain:Blocks, Stimulators, Pumps


Background

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


Nerve blocks i

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


Nerve blocks ii

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)


Nerve blocks iii

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


Trigger point injection i

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


Trigger point injection ii

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


Trigger point injection iii

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; 1999:160.


Trigger point injection iii1

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; 1999:159.


Tourniquet or bier block

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, Esmarch’s bandage), proximal tourniquet (eg, systolic BP + 100), slow release after ~20 min

  • Medications: local anesthetic, many others (sympatholytic, anti-inflammatory)


Peripheral nerve injection

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


Paravertebral nerve root injection

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


Epidural injection i

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)


Interventional approaches to chronic pain blocks stimulators pumps

Trans-Ligamental Injection

Reproduced with permission from Covino BG, Scott DB. Handbook of Epidural Anaesthesia and Analgesia. New York, NY: Grune & Stratton, Inc; 1985:90.


Interventional approaches to chronic pain blocks stimulators pumps

Sacral Extradural Injection

Reproduced with permission from Eriksson E, ed. Illustrated Handbook in Local Anaesthesia. 2nd ed. London, Eng: Lloyd-Luke (Medical Books) Ltd; 1979:135.


Epidural injection ii

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


Interventional approaches to chronic pain blocks stimulators pumps

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


Intra articular injection

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


Interventional approaches to chronic pain blocks stimulators pumps

C 3-4 Facet Injection (Lateral View)


Interventional approaches to chronic pain blocks stimulators pumps

S1 Root Block (Trans-Sacral)


Sympathetic block

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


Interventional approaches to chronic pain blocks stimulators pumps

Lumbar Sympathetic Block (Lateral View)


Plexus block celiac hypogastric

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 (<10%) 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


Interventional approaches to chronic pain blocks stimulators pumps

Celiac Block (Lateral View)


Interventional approaches to chronic pain blocks stimulators pumps

CT-Guided Celiac Block


Spinal cord stimulation

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)


Possible risks scs or pump

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…


Implanted pumps for pain

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…


Theoretical benefits of it rx i

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


Theoretical benefits of it rx ii

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; 1998:915-983.


Algogenic neuropoiesis

“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.


It analgesia evidence

IT Analgesia: Evidence

  • Abundant preclinical proof of IT analgesia using various agents, singly or in combination

  • Narrative reviews from 1980s–1990s summarize clinical effectiveness and conclude IT analgesia generally is safe, well-tolerated, effective for acute or chronic cancer and noncancer pain


It evidence limitations i

IT Evidence: Limitations (I)

  • Level 5 clinical evidence (uncontrolled case reports/series)—like >90% 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?


It evidence limitations ii

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. 2000;20:S37-S43.


Intrathecal opioids prospects

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


Prudent practice

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


A thought

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)


Conclusions

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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