Interventional ApproachesInterventional Approachesto Chronic Pain:to Chronic Pain:

Blocks, Stimulators, PumpsBlocks, Stimulators, Pumps

BackgroundBackground• Neurosurgical ablative treatments for pain Neurosurgical ablative treatments for pain

since 19th century but now infrequently used since 19th century but now infrequently used • Ablation eclipsed by percutaneous injections Ablation eclipsed by percutaneous injections

or therapies that target central or peripheral or therapies that target central or peripheral pathwayspathways– Nerve blocksNerve blocks– Spinal stimulationSpinal stimulation– PumpsPumps

Nerve Blocks (I)Nerve Blocks (I)

• Diagnostic: local anesthetic only, to clarify Diagnostic: local anesthetic only, to clarify mechanism or simulate effects of therapymechanism or simulate effects of therapy

• Therapeutic: anesthetize a site or pathway Therapeutic: anesthetize a site or pathway temporarily (local anesthetic) or “permanently” temporarily (local anesthetic) or “permanently” (lytic agent), or reduce inflammation (lytic agent), or reduce inflammation (corticosteroid)(corticosteroid)

• A block may be both diagnostic and therapeutic, A block may be both diagnostic and therapeutic, eg, sympathetic block or trigger-point injectioneg, sympathetic block or trigger-point injection

Nerve Blocks (II)Nerve Blocks (II)• Common blocks for chronic pain includeCommon blocks for chronic pain include

– Trigger-point injectionTrigger-point injection– Tourniquet or Bier blockTourniquet or Bier block– Peripheral nerve injection (eg, ilioinguinal, lateral Peripheral nerve injection (eg, ilioinguinal, lateral

femoral cutaneous, greater occipital)femoral cutaneous, greater occipital)– Paravertebral (nerve root) injectionParavertebral (nerve root) injection– Epidural injectionEpidural injection– Intra-articular (eg, facet, SI) injectionIntra-articular (eg, facet, SI) injection– Sympathetic block (cervical, lumbar)Sympathetic block (cervical, lumbar)– Plexus block (celiac, hypogastric)Plexus block (celiac, hypogastric)

Nerve Blocks (III)Nerve Blocks (III)• Case reports, preclinical data support long-Case reports, preclinical data support long-

lasting effects of local anesthetic blockadelasting effects of local anesthetic blockade– RCTs support lytic celiac blockRCTs support lytic celiac block

• However, unclear how much clinical However, unclear how much clinical improvement reflects placebo effects, irrelevant improvement reflects placebo effects, irrelevant cues, systemic absorption of local anesthetic, cues, systemic absorption of local anesthetic, expectations expectations

• Side effects possibleSide effects possible• Rarely successful as a “stand-alone” strategy for Rarely successful as a “stand-alone” strategy for

chronic painchronic pain

Trigger-Point Injection ITrigger-Point Injection I

• Essential criteriaEssential criteria– Taut band palpable (if muscle accessible)Taut band palpable (if muscle accessible)– Exquisite spot tenderness of a nodule in a taut bandExquisite spot tenderness of a nodule in a taut band– Pressure on tender nodule reproduces painPressure on tender nodule reproduces pain– Range of motion with stretch limited by painRange of motion with stretch limited by pain

• Confirmatory observationsConfirmatory observations– Visual or tactile identification of local twitch responseVisual or tactile identification of local twitch response– Local twitch response on needling tender noduleLocal twitch response on needling tender nodule– Pain/hyperesthesia in recognized patternPain/hyperesthesia in recognized pattern– Activity in tender nodule on EMGActivity in tender nodule on EMG

Trigger-Point Injection IITrigger-Point Injection II

• Trigger points may refer painTrigger points may refer pain– Toward the periphery (eg, suboccipital, infraspinatus)Toward the periphery (eg, suboccipital, infraspinatus)– Proximally or medially (eg, biceps brachii)Proximally or medially (eg, biceps brachii)– Locally (eg, serratus posterior inferior)Locally (eg, serratus posterior inferior)

• TechniquesTechniques– Needle only (no injection)Needle only (no injection)– Local anesthetic onlyLocal anesthetic only– Local anesthetic + glucocorticoid (evidence?)Local anesthetic + glucocorticoid (evidence?)– Botulinum toxin type ABotulinum toxin type A

Trigger-Point Injection IIITrigger-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 IIITrigger-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 BlockTourniquet or Bier Block• Facilitates mobilization of upper or lower extremity Facilitates mobilization of upper or lower extremity

in known or suspected CRPSin known or suspected CRPS• Same technique for sympathetically-maintained Same technique for sympathetically-maintained

versus sympathetic-independent painversus sympathetic-independent pain• Many variants: all use IV cannulation, drainage of Many variants: all use IV cannulation, drainage of

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

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

Peripheral Nerve InjectionPeripheral Nerve Injection• Spontaneous entrapment syndromesSpontaneous entrapment syndromes

– Greater occipital (occipital neuralgia)Greater occipital (occipital neuralgia)– Lateral femoral cutaneous (meralgia paresthetica)Lateral femoral cutaneous (meralgia paresthetica)– IlioinguinalIlioinguinal

• Post-incisional or post-traumatic neuromaPost-incisional or post-traumatic neuroma– Cranial (post-craniotomy)Cranial (post-craniotomy)– Intercostal (post-thoracotomy)Intercostal (post-thoracotomy)– Abdominal wall (trochar sites)Abdominal wall (trochar sites)– HerniorrhaphyHerniorrhaphy

• Local anesthetic + glucocorticoidLocal anesthetic + glucocorticoid

Paravertebral (Nerve Root) InjectionParavertebral (Nerve Root) Injection• DiagnosticDiagnostic

– Establish or confirm anatomic mechanism of pain (eg, Establish or confirm anatomic mechanism of pain (eg, atypical dermatomal distribution in disk disease or atypical dermatomal distribution in disk disease or multilevel foraminal stenosis)multilevel foraminal stenosis)

• TherapeuticTherapeutic– Deposit local anesthetic plus glucocorticoid via Deposit local anesthetic plus glucocorticoid via

paravertebral and/or transforaminal approachparavertebral and/or transforaminal approach• TechniqueTechnique

– Fluoroscopy or CT essential to validate, document needle Fluoroscopy or CT essential to validate, document needle placementplacement

– Radiopaque contrast outlines/tracks rootRadiopaque contrast outlines/tracks root

Epidural Injection (I)Epidural Injection (I)• Employed for decades using various techniques, Employed for decades using various techniques,

materials, and patients materials, and patients – Poor documentation of diagnosis, pain, technique, Poor documentation of diagnosis, pain, technique,

outcomesoutcomes• Limited RCT evidence of efficacy in Limited RCT evidence of efficacy in

subpopulations, but most reports are case seriessubpopulations, but most reports are case series• Techniques (glucocorticoid + local anesthesic)Techniques (glucocorticoid + local anesthesic)

– TranslaminarTranslaminar– TransforaminalTransforaminal– Caudal (useful if prior lumbar surgery, scarring)Caudal (useful if prior lumbar surgery, scarring)

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

Trans-Ligamental InjectionTrans-Ligamental Injection

Sacral Extradural InjectionSacral 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 inApplied for symptomatic relief in– Disk protrusion with radiculopathyDisk protrusion with radiculopathy– Spinal stenosis (circumferential or foraminal)Spinal stenosis (circumferential or foraminal)– Acute pain, local inflammation of vertebral fracture (Acute pain, local inflammation of vertebral fracture (

subsequent vertebroplasty)subsequent vertebroplasty)– ? Acute herpes zoster, using local anesthetic alone? Acute herpes zoster, using local anesthetic alone

• May facilitate rehabilitation, avert surgery when May facilitate rehabilitation, avert surgery when applied within multidisciplinary frameworkapplied within multidisciplinary framework

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

Intra-Articular InjectionIntra-Articular Injection

• Facet, large joints, sacroiliac most commonFacet, large joints, sacroiliac most common• DiagnosticDiagnostic

– Clarify clinical impression of a “facet syndrome” or “SI Clarify clinical impression of a “facet syndrome” or “SI joint pain”joint pain”

– (Facet:) simulate results of potential spinal fusion or (Facet:) simulate results of potential spinal fusion or denervation of medial branch of dorsal ramusdenervation of medial branch of dorsal ramus

• Therapeutic (local anesthetic + glucocorticoid)Therapeutic (local anesthetic + glucocorticoid)– Reduce inflammation, painReduce inflammation, pain– Increase mobility, facilitate rehabilitation Increase mobility, facilitate rehabilitation

• Controversy as to efficacy and effectivenessControversy as to efficacy and effectiveness

C 3-4 Facet Injection (Lateral View)C 3-4 Facet Injection (Lateral View)

S1 Root Block (Trans-Sacral)S1 Root Block (Trans-Sacral)

Sympathetic BlockSympathetic Block• DiagnosticDiagnostic

– Superior cervical (“stellate”) ganglionSuperior cervical (“stellate”) ganglion– LumbarLumbar– Note need for (but insurers’ reluctance to pay for) placebo Note need for (but insurers’ reluctance to pay for) placebo

controlscontrols• TherapeuticTherapeutic

– CRPS of upper, lower extremityCRPS of upper, lower extremity– Facial neuralgiasFacial neuralgias

• TechniqueTechnique– Local anestheticLocal anesthetic– Neurolytic Neurolytic

Lumbar Sympathetic Block (Lateral View)Lumbar Sympathetic Block (Lateral View)

Plexus Block (Celiac, Hypogastric)Plexus Block (Celiac, Hypogastric)• Visceral nociceptive afferent pathways are heterogeneous: Visceral nociceptive afferent pathways are heterogeneous:

sympathetic (eg, celiac), parasympathetic (eg, hypogastric)sympathetic (eg, celiac), parasympathetic (eg, hypogastric)• Meta-analysis indicates efficacy of celiac block for abdominal Meta-analysis indicates efficacy of celiac block for abdominal

cancer pain, but case series show little benefit (<10%) in cancer pain, but case series show little benefit (<10%) in chronic pancreatitischronic pancreatitis

• Case series of hypogastric block for perineal painCase series of hypogastric block for perineal pain• TechniqueTechnique

– Fluoroscopy or CT essential for safety, documentationFluoroscopy or CT essential for safety, documentation– Reversible block with local anestheticReversible block with local anesthetic– Neurolysis with alcohol, phenolNeurolysis with alcohol, phenol

Celiac Block (Lateral View)Celiac Block (Lateral View)

CT-Guided Celiac BlockCT-Guided Celiac Block

Spinal Cord StimulationSpinal Cord Stimulation• Background: peripheral electrical stimulation for pain Background: peripheral electrical stimulation for pain

control since prehistory; recent “gate theory” control since prehistory; recent “gate theory” • Retrospective, uncontrolled case series show that SCS Retrospective, uncontrolled case series show that SCS

can reduce intensity of neuropathic pain can reduce intensity of neuropathic pain • Biases in existing literature (lack of blinding, Biases in existing literature (lack of blinding,

heterogeneity of interventions/assessments, small heterogeneity of interventions/assessments, small numbers) confound its interpretation numbers) confound its interpretation

• Recent 6-month RCT: “with careful selection of patients Recent 6-month RCT: “with careful selection of patients and successful test stimulation, SCS is safe, reduces pain and successful test stimulation, SCS is safe, reduces pain and improves HRQOL in chronic RSD” (Kemler MA, et al. and improves HRQOL in chronic RSD” (Kemler MA, et al. N Engl J Med.N Engl J Med. 2000; N = 36) 2000; N = 36)

Possible Risks (SCS or Pump)Possible Risks (SCS or Pump)

• Non-specific: electrical, mechanical (migration, Non-specific: electrical, mechanical (migration, separation of electrode or catheter) failureseparation of electrode or catheter) failure

• Route-specific: infection, fibrosis, extrusionRoute-specific: infection, fibrosis, extrusion• Drug-specific (pump): neurotoxicity, sedation, Drug-specific (pump): neurotoxicity, sedation,

constipation, hypotension…constipation, hypotension…• For opioids (pump): constipation, urinary For opioids (pump): constipation, urinary

retention, nausea, impotence, nightmares, retention, nausea, impotence, nightmares, pruritus, edema, sweating, fatigue…pruritus, edema, sweating, fatigue…

Implanted Pumps for PainImplanted Pumps for Pain• Spinal anesthesia ~100 ySpinal anesthesia ~100 y• Selective spinal opioid analgesia ~25 ySelective spinal opioid analgesia ~25 y• Early chronic use of opioid PCEA supplanted by Early chronic use of opioid PCEA supplanted by

intrathecal cannulation intrathecal cannulation • Single agents: opioids, local anesthetics, NSAIDs, Single agents: opioids, local anesthetics, NSAIDs,

clonidine, cholinomimetics, calcium channel clonidine, cholinomimetics, calcium channel blockers, GABA-A and -B, peptides, NMDA blockers, GABA-A and -B, peptides, NMDA antagonists, adenosineantagonists, adenosine

• Combinations: opioid-opioid, opioid-local Combinations: opioid-opioid, opioid-local anesthetic, morphine-clonidine…anesthetic, morphine-clonidine…

Theoretical Benefits of IT Rx (I)Theoretical Benefits of IT Rx (I)

• ““Targeting” offers dosage reductionsTargeting” offers dosage reductions• Only route possible for certain drugsOnly route possible for certain drugs• Fewer side effects from decreased and Fewer side effects from decreased and

spatially restricted dosagespatially restricted dosage• Greater efficacy from targeted, higher Greater efficacy from targeted, higher

concentrations (eg, in neuropathic pain) concentrations (eg, in neuropathic pain) and locally applied combinationsand locally applied combinations

Theoretical Benefits of IT Rx (II)Theoretical Benefits of IT Rx (II)

• Nociceptive activity provokes persistent Nociceptive activity provokes persistent functional and morphologic changes functional and morphologic changes

• Pain, especially chronic pain, is a diseasePain, especially chronic pain, is a disease• Spinal analgesic therapy = “dorsal horn Spinal analgesic therapy = “dorsal horn

amnesia”*amnesia”*• ““Combination analgesic chemotherapy”*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 Transformation of neuronal morphology

and function as the result of nociception*and function as the result of nociception*• ““Poiesis” = organized creation, growthPoiesis” = organized creation, growth• A highly organized process (CaA highly organized process (Ca++++, second , second

messengers, oxidative stress, novel gene messengers, oxidative stress, novel gene expression, growth factors, apoptosis)expression, growth factors, apoptosis)

*See Walker S, et al. Anesth Analg. In press.

IT Analgesia: EvidenceIT Analgesia: Evidence• Abundant preclinical proof of IT analgesia Abundant preclinical proof of IT analgesia

using various agents, singly or in using various agents, singly or in combination combination

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

IT Evidence: Limitations (I)IT Evidence: Limitations (I)

• Level 5 clinical evidence (uncontrolled case Level 5 clinical evidence (uncontrolled case reports/series)—like >90% of all pain literature reports/series)—like >90% of all pain literature

• Inclusion based upon failure of prior therapy but Inclusion based upon failure of prior therapy but unclear whether/how therapy optimizedunclear whether/how therapy optimized

• Nonuniform or unknown Dx, pain/QOL scoresNonuniform or unknown Dx, pain/QOL scores• Side effects vs effects: “different dimensions”Side effects vs effects: “different dimensions”• Limited psychologic, toxicologic dataLimited psychologic, toxicologic data• Effect of drug redistribution?Effect of drug redistribution?

IT Evidence: Limitations (II)IT Evidence: Limitations (II)• No controls = UNDEFINABLE relative efficacy!No controls = UNDEFINABLE relative efficacy!• Without data on relative efficacy, algorithms/guidelines Without data on relative efficacy, algorithms/guidelines

follow “practice-based evidence”follow “practice-based evidence”• For evidence-based practice, RCTs or CCTs are For evidence-based practice, RCTs or CCTs are

necessary to control for expectations, psychosocial and necessary to control for expectations, psychosocial and placebo/nocebo effectsplacebo/nocebo effects

• ““Consort” statement needed for pain trialsConsort” statement needed for pain trials• ““Need for additional large published controlled studies… Need for additional large published controlled studies…

highlighted” by review of Bennett et al*highlighted” by review of Bennett et al*

*See Bennett G, et al. J Pain Symptom Manage. 2000;20:S37-S43.

Intrathecal Opioids: ProspectsIntrathecal Opioids: Prospects• Opportunity for translational research on “dorsal Opportunity for translational research on “dorsal

horn amnesia”horn amnesia”• Need for uniformity, control groupsNeed for uniformity, control groups• Requirement for appropriately powered trials: Requirement for appropriately powered trials:

“size does matter” “size does matter” • Control for drug interactionsControl for drug interactions• Long-term follow-upLong-term follow-up• Clinical consensus drives initial opioid use alone, Clinical consensus drives initial opioid use alone,

but may be better to start with combinationsbut may be better to start with combinations

Prudent PracticePrudent Practice• Any nerve block, no matter how deftly and Any nerve block, no matter how deftly and

carefully performed, can lead to sudden carefully performed, can lead to sudden complications related to intraneural, complications related to intraneural, intraspinal, or intravascular injectionintraspinal, or intravascular injection

• Anyone who considers performing a nerve Anyone who considers performing a nerve block should provide monitoring, vigilance block should provide monitoring, vigilance during and afterwards, and resources for during and afterwards, and resources for prompt resuscitationprompt resuscitation

A ThoughtA Thought• Interventional approaches often are reserved for patients Interventional approaches often are reserved for patients

with well-established problems, failure of other Rx, and with well-established problems, failure of other Rx, and pronounced disabilitypronounced disability

• Do we miss an opportunity for early, cost-effective Do we miss an opportunity for early, cost-effective preventive treatment by reserving interventions for those preventive treatment by reserving interventions for those least likely to benefit? least likely to benefit?

• Established neuropoiesis, entrenched pain behavior, Established neuropoiesis, entrenched pain behavior, proven self-advocacy in disabled role may explain data proven self-advocacy in disabled role may explain data on low likelihood of return to workon low likelihood of return to work

• ““Youth is a wonderful thing; what a crime to waste it on Youth is a wonderful thing; what a crime to waste it on children” (George Bernard Shaw)children” (George Bernard Shaw)

ConclusionsConclusions• Best to reserve blocks, other invasive Rx for when other Best to reserve blocks, other invasive Rx for when other

modalities fail?modalities fail?• Substantial risks and benefits of SCS, IT Rx Substantial risks and benefits of SCS, IT Rx • Stand-alone interventions less likely to succeed than Stand-alone interventions less likely to succeed than

multidisciplinary onesmultidisciplinary ones• Irresistible force (evidence-based medicine) now is Irresistible force (evidence-based medicine) now is

meeting immovable object (case reports, customary meeting immovable object (case reports, customary practice)practice)

• Needed: outcomes data on effectiveness and large RCTs Needed: outcomes data on effectiveness and large RCTs re: efficacyre: efficacy