Interventional approaches for Chronic Pain

Question 1

Indications for interventional pain therapies

Answer 1

1. Uncontrolled pain despite systemic analgesics
2. Unacceptable systemic analgesic adverse effects

Question 2

Trigger point injections

Answer 2

• myofascial pain
• trigger point on exam
  
  • hyperirritable nodule in skeletal muscle
  • pain on palpation, compression
  • refers pain
• local anesthetic injected
• dry needling
• acupuncture
• botox

Question 3

Botox

Answer 3

• neuroparalytic agent produced from clostridium botulinum
• inhibits acetylcholine release at NMJ
• used for migraine, interstitial cystitis, chronic myofascial pain
• spasticity
• q12 weeks to minimize antibody development

Question 4

Peripheral nerve blocks

Answer 4

• plexopathy or peripheral nerve
• repeated injections
• continuous infusion with catheter placed
• Risk:
  
  • infection
  • local anesthetic toxicity
  • displacement
  • knotting

Question 5

Neurolytic blocks:

Chemical

Answer 5

• alcohol and phenol
• anesthetic and neurolytic effects

Question 6

Neurolytic blocks:

Radiofrequency ablation or pulsed treatment

Answer 6

• FR neurotomy
• heat destruction of neural tissue
• high frequency electrical current
• Uses:
  
  • spinal facet
  • trigeminal ganglia
  • dorsal root ganglia
  • spinal sympathetic ganglia
• pulsed radiofrequency
  
  • high voltage bursts
  • some thermal damage
  • neuromodulation
  • better for trigger points, dorsal root ganglia, peripheral neuropathy

Question 7

Sympathetic nervous system block :

Celiac Plexus Block

Answer 7

• Visceral pain from pancreatic cancer, upper abdominal tumours
• May reduce opioid use and SE
• 80-90% relief x 3 months
• percutaneous or CT guided, or endoscopically done
• outpatient treatment
• SE:
  
  • transient diarrhea
  • orthostatic hypotension
  • rare : paralysis, arotic dissection

Question 8

Lumbar Sympathetic Blocks

Answer 8

• injection through anterolateral aspect of vertbral body on ispilateral side of pain
• Indications :
  
  • kidney pain
  • intractable lower extremity pain
  • PVD
  • leg ulcers
  • CRPS
  • phantom pain
  • diabetic neuropathy
  • testicular pain
• reduces rest pain, increased cutaneous blood flow
• 6 months relief

Question 9

Stellate Ganglion Block

Answer 9

• collection of sympathetic nerves in neck at C6-7 level.
• located in front of vertbral body
• Useful for :
  
  • refractory angina
  • CRPS
  • PVD
  • Raynaud’s brachial plexus
  • Pain in face, head, arms and chest
• alternative is T2-T3 paravertebral sympathectomy by RF ablation

Question 10

Superior hypogastric plexus block

Sympathetic blockade

Answer 10

• Pelvic visceral pain from gyne, colorectal, GU ca
• long lasting relief

Question 11

Ganglion Impar Block

Answer 11

• Intractable perineal pain

Question 12

Sympathetic blockade : MOA

Answer 12

• Interruption of afferent sympathetic nerves

Question 13

Neuraxial Neurolysis

Answer 13

• chemical posterior rhizotomy
• Subarachnoid neurolysis
  
  • few dermatomes only
  • advanced cancer
• surgical or chemical cordotomy
  
  • upper lumbar, lower thoracic dermatomes
• high complication rates,
• may be acceptable for severe pain at EOL
  
  • sensory, motor, autonomic derangements
  • ineffective relief
  • motor weakness
  • incontinence
• Not helpful for extensive, poorly localized pain or neuropathic pain

Question 14

Spinal Analgesia

Answer 14

• Peripheral nociceptors of afferent first order neurons in spine
  
  • alpha adrenegic
  • opioid
  • GABA
  • Ca2+ channels
  • release of glutamate and substance P
• Spinal neuron post synaptic membrane
  
  • NMDA
  • Opioids
  • alpha adrenergic
  • GABA
  • Ca2+

Question 15

Spinal Opioids

Answer 15

• Morphine
• HM
• fentanyl
• delivered directly to opioid receptors in dorsal horn of spinal grey matter
• opioid receptors are in peripheral afferents and post synaptic second order neurons
• opioids inhibit synaptic transmission between primary afferent and second order neurons

Question 16

Adverse effects of spinal opioids

Answer 16

• incidence lower as usually patients alreadys tolerant
• naloxone 0.4 mg or infusion 1-5 ug/kg/hour
• Respiratory depression possible with initiation and dose adjustments
• delayed resp depression from cephalad migration
• sweating, hypogonadotrophic hypogonadism
• OIN rare

Question 17

Non opioid spinal analgesics

Answer 17

• Bupivicaine
  
  • lidocaine avoided for toxicity
  • reduce nociceptic input
  • reduce sensitization of spinal cord neurons
• can achieve pain relief without motor blockade
• easier with epidural vs intrathecal
• high dose bupi, dense block for severe pain EOL

Clonidine

• alpha adrenergic
• AE: hypotension, bradycardia

Baclofen

• spasticity
• analgesic for neuropathic pain
• baclofen withdrawal can be fatal

Ziconotide

• not used

Question 18

Indications for Spinal Analgesia in Palliative Care

Answer 18

• Works best for deep, constant somatic pain
• cutaneous, intermittent, path fracture, MBO less effective
• extreme tolerance = opioid +non opioid

Question 19

Contraindications for Spinal analgesia

Answer 19

• Sepsis
• coagulopathy
• local infection
• can make informed decision to leave or place catheter at EOL even with infection if pain control felt to override SE
• NOT a CI:
  
  • ongoing chemo or radiation
  • spinal mets are location dependent

Question 20

Implantable pumps

Answer 20

• filling intervals q1-2 months
• small resevoir
• usually need custom compounded solutions
• typically for longer life expectancy
• potential for overdose if solution injected into skin instead of refill port

Question 21

Implanted or externalized Port

Answer 21

• external pump can be managed by some patients at hone

Question 22

Epidural Complications

Answer 22

Epidural Fibrosis

• Symptoms
  
  • back pain
  • paresthesias on injection
  • loss of analgesia
  • no infection
• Replace epidural or change to IT

Epidural infection or abscess

• Symptoms
  
  • back and extremity pain
  • weakness
  • sensory abnormalities
  • fever, leukocytosis
• Dx:
  
  • catheter aspirate, gram stain, culture
  • MRI
• Tx:
  
  • aspirate cathether to decompress
  • IV antibiotics
  • remove catheter

Question 23

Intrathecal Complications

Answer 23

Meningitis

• Sx:
  
  • severe HA
  • cervical stiffness
  • fever, photophobia
• Dx: cathether aspirate
  
  • cell count, gm stain, glucose, culture
• Tx:
  
  • antibiotics
  • remove cathether

Subarachnoid Granuloma

• Sx:
  
  • SCC
  • weakness
  • severe pain at level
• Dx:
  
  • MRI, CT myelogram
• Tx:
  
  • d/c spinal analgesics
  • surgery if SCC

Question 24

Complications Common to both Epidural and Intrathecals

Answer 24

Catheter dislodgement

• Sx:
  
  • loss of analgesia
  • opioid withdrawal
• Dx:
  
  • Xray with contrast
  • physical exam
• Tx:
  
  • Replacement
  • tunnelled line

Pump Malfunction

• Sx:
  
  • loss of analgesia, opioid withdrawal
• Dx:
  
  • pump analysis
• Tx: replace pump

Infection

• Sx: erythema, pain, fever
• Dx: culture cathether exit site, aspirate
• Tx: replace line, antibiotics, local site care

Question 25

Intracerebroventricular opioids

Answer 25

• indications:
  
  • intractable pain
  • last resort, rarely done
  • inaccesible spinal CSF
  • intractable head and neck pain

Question 26

Cordotomy

Answer 26

• spinothalamic
• intractable unilateral somatic pain in lower body

Midline myelotomy - midline visceral pain

Dorsal root entry zone lesioning - rare for brachial plexopathy

Question 27

Vertebral augmentation

Answer 27

• Kyphoplasty - balloon + cement
• Vertebroplasty - just cement via needle
• 80% good to excellent relief for non malignant OP #
• 50-60% relief with malignant #
• MRI/CT
• Contraindications:
  
  • SCC with clinical myelopathy
  • overt spinal instability
  • osteomyelitis
  • posterior verebral defect
  • epidural tumour
  • cervical fractures
• Risk of extrusion of cement into spinal canal
• Risk of cement venous embolism