interventional approaches to chronic pain: blocks, stimulators, pumps
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DESCRIPTIONInterventional 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 - PowerPoint PPT Presentation
Interventional Approachesto Chronic Pain:Blocks, Stimulators, Pumps
BackgroundNeurosurgical ablative treatments for pain since 19th century but now infrequently used Ablation eclipsed by percutaneous injections or therapies that target central or peripheral pathwaysNerve blocksSpinal stimulationPumps
Nerve Blocks (I)Diagnostic: local anesthetic only, to clarify mechanism or simulate effects of therapyTherapeutic: 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)Common blocks for chronic pain include Trigger-point injectionTourniquet or Bier blockPeripheral nerve injection (eg, ilioinguinal, lateral femoral cutaneous, greater occipital)Paravertebral (nerve root) injectionEpidural injectionIntra-articular (eg, facet, SI) injectionSympathetic block (cervical, lumbar)Plexus block (celiac, hypogastric)
Nerve Blocks (III)Case reports, preclinical data support long-lasting effects of local anesthetic blockadeRCTs support lytic celiac blockHowever, unclear how much clinical improvement reflects placebo effects, irrelevant cues, systemic absorption of local anesthetic, expectations Side effects possibleRarely successful as a stand-alone strategy for chronic pain
Trigger-Point Injection IEssential criteriaTaut band palpable (if muscle accessible)Exquisite spot tenderness of a nodule in a taut bandPressure on tender nodule reproduces painRange of motion with stretch limited by painConfirmatory observationsVisual or tactile identification of local twitch responseLocal twitch response on needling tender nodulePain/hyperesthesia in recognized patternActivity in tender nodule on EMG
Trigger-Point Injection IITrigger points may refer painToward the periphery (eg, suboccipital, infraspinatus)Proximally or medially (eg, biceps brachii)Locally (eg, serratus posterior inferior)TechniquesNeedle only (no injection)Local anesthetic onlyLocal anesthetic + glucocorticoid (evidence?)Botulinum toxin type A
Trigger-Point Injection IIIReproduced 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 IIIReproduced 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 BlockFacilitates mobilization of upper or lower extremity in known or suspected CRPSSame technique for sympathetically-maintained versus sympathetic-independent painMany variants: all use IV cannulation, drainage of blood (gravity, Esmarchs bandage), proximal tourniquet (eg, systolic BP + 100), slow release after ~20 minMedications: local anesthetic, many others (sympatholytic, anti-inflammatory)
Peripheral Nerve InjectionSpontaneous entrapment syndromesGreater occipital (occipital neuralgia)Lateral femoral cutaneous (meralgia paresthetica)IlioinguinalPost-incisional or post-traumatic neuromaCranial (post-craniotomy)Intercostal (post-thoracotomy)Abdominal wall (trochar sites)HerniorrhaphyLocal anesthetic + glucocorticoid
Paravertebral (Nerve Root) InjectionDiagnosticEstablish or confirm anatomic mechanism of pain (eg, atypical dermatomal distribution in disk disease or multilevel foraminal stenosis)TherapeuticDeposit local anesthetic plus glucocorticoid via paravertebral and/or transforaminal approachTechniqueFluoroscopy or CT essential to validate, document needle placementRadiopaque contrast outlines/tracks root
Epidural Injection (I)Employed for decades using various techniques, materials, and patients Poor documentation of diagnosis, pain, technique, outcomesLimited RCT evidence of efficacy in subpopulations, but most reports are case seriesTechniques (glucocorticoid + local anesthesic)TranslaminarTransforaminalCaudal (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 Injection
Sacral Extradural InjectionReproduced 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)Applied for symptomatic relief inDisk protrusion with radiculopathySpinal stenosis (circumferential or foraminal)Acute pain, local inflammation of vertebral fracture ( subsequent vertebroplasty)? Acute herpes zoster, using local anesthetic aloneMay facilitate rehabilitation, avert surgery when applied within multidisciplinary framework
Layering of Contrast in Epidural Space (C5-6 Epidural)
Intra-Articular InjectionFacet, large joints, sacroiliac most commonDiagnosticClarify clinical impression of a facet syndrome or SI joint pain(Facet:) simulate results of potential spinal fusion or denervation of medial branch of dorsal ramusTherapeutic (local anesthetic + glucocorticoid)Reduce inflammation, painIncrease mobility, facilitate rehabilitation Controversy as to efficacy and effectiveness
C 3-4 Facet Injection (Lateral View)
S1 Root Block (Trans-Sacral)
Sympathetic BlockDiagnosticSuperior cervical (stellate) ganglionLumbarNote need for (but insurers reluctance to pay for) placebo controlsTherapeuticCRPS of upper, lower extremityFacial neuralgiasTechniqueLocal anestheticNeurolytic
Lumbar Sympathetic Block (Lateral View)
- 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 (
Celiac Block (Lateral View)
CT-Guided Celiac Block
Spinal Cord StimulationBackground: 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)Non-specific: electrical, mechanical (migration, separation of electrode or catheter) failureRoute-specific: infection, fibrosis, extrusionDrug-specific (pump): neurotoxicity, sedation, constipation, hypotensionFor opioids (pump): constipation, urinary retention, nausea, impotence, nightmares, pruritus, edema, sweating, fatigue
Implanted Pumps for PainSpinal anesthesia ~100 ySelective spinal opioid analgesia ~25 yEarly 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, adenosineCombinations: opioid-opioid, opioid-local anesthetic, morphine-clonidine
Theoretical Benefits of IT Rx (I)Targeting offers dosage reductionsOnly route possible for certain drugsFewer side effects from decreased and spatially restricted dosageGreater efficacy from targeted, higher concentrations (eg, in neuropathic pain) and locally applied combinations
Theoretical Benefits of IT Rx (II)Nociceptive activity provokes persistent functional and morphologic changes Pain, especially chronic pain, is a diseaseSpinal 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 NeuropoiesisTransformation of neuronal morphology and function as the result of nociception*Poiesis = organized creation, growthA 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: EvidenceAbundant 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
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 optimizedNonuniform or unknown Dx, pain/QOL scoresSide effects vs effects: different dimensionsLimited psychologic, toxicologic dataEffect of drug redistribution?
IT Evidence: Limitations (II)No controls = UNDEFINABLE relative efficacy!Without data on relative efficacy, algorithms/guidelines follow practice-based evidenceFor evidence-based practice, RCTs or CCTs are necessary to control for expectations, psychosocial and placebo/nocebo effectsConsort statement needed for pain trialsNeed 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: ProspectsOpportunity for translational research on dorsal horn amnesiaNeed for uniformity, co