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Palliative > Interventional Approaches for Pain > Flashcards

Interventional Approaches for Pain Flashcards

1
Q

Prevalence of inadequate pain control in advance cancer

A

10-30%

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2
Q

Indications for interventional pain control

A
  • Uncontrolled pain despite adequate systemic analgesics

- Unacceptable systemic analgesics adverse effects

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3
Q

Characteristics increasing the likelihood of needing procedural pain therapy

A

Neuropathic pain

Somatic pain that is sharp and severe

Pain that fluctuates markedly

Significant side effects with medication

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4
Q

Trigger point injections - indications

A

Myofascial pain syndromes

  • May involve any muscle
  • Can be either a primary problem or occur secondary infection, intervertebral disc disease, vertebral compression fracture, bony mets
  • On exam, must have a specific ‘trigger point’: Hyperirritable nodule in skeletal muscle that may be palpable, painful on compression, and can cause characteristic referred pain or autonomic phenomena
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5
Q

Trigger point injection - process

A
  • Consider physical therapy alone, or other alternative txs (dry needling, acupuncture, pulse radiofrequency, botox)
  • Local anesthetic injected into the trigger point
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6
Q

Intra-articular injections: Indications and risks

A
  • May be used in arthritis or joint-related pain
  • Most commonly, corticosteroids

Side effects:

  • Infection
  • Bleeding
  • Nerve injury
  • Joint destruction
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7
Q

Botox injections - mechanism of action

A
  • Neuroparalytic agent produced by Clostridium botulinum
  • Irreversibly inhibits acetylcholine release at the neuromuscular junction, causing localised chemodenervation at the target organ with minimal systemic adverse effects
  • May also block peripheral sensitization and indirectly reduce central sensitization
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8
Q

Botox: Indications

A
  • Spasticity and movement disorders

Poorer evidence for:

  • Migraines
  • Interstitial cystitis
  • Chronic myofascial pain
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9
Q

Botox - risks and effectiveness

A
  • Generally safe and well tolerated and may be repeated
  • When effective, effects usually evident approximately 1 week after injection
  • Benefit typically lasts 3-4 months then fades
  • Repeated administration may lead to diminishing effects due to the development of neutralizing antibodies, and as such spacing of at least 12 weeks is recommended
  • If diminishing effects develops, rotate to a different commercial formulation
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10
Q

Peripheral nerve blocks - indications

A
  • Useful for pain in the distribution of a peripheral nerve or plexus
  • Most often used perioperatively, or for pain due to tumour, pathologic fractures, or ischemia
  • May be either for repeated or continuous local anesthetic blockade (eg with a catheter placed near the peripheral nerve)
  • Peripheral nerve catheters can be maintained for several weeks
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11
Q

Risks of peripheral nerve blocks

A

Long-term catheters:

  • Infection
  • Local anesthetic toxicity
  • Catheter displacement
  • Technical difficulties (catheter knotting)
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12
Q

Neurolytic blocks - agents used

A

Phenol

  • Local anesthetic effects and neurolytic effects (virtually painless injection)
  • If dosed excessively or accidentally injected intravascularly, may cause convulsions, CNS depression, or cardiovascular collapse

Ethanol

  • Few significant adverse effects from a systemic perspective
  • May cause pain on injection

Little data on choosing an agent

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13
Q

Radiofrequency neurotomy

A
  • Destruction of neural tissue with heat centered by a high frequency electrical current

May be conventional (thermal) radiofrequency neurotomy, or pulsed radiofrequency (short, high volume bursts)

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14
Q

Sympathetic nervous system block

A
  • Sympathetic blockade with either local anesthetic or neurolytic solutions
  • Local anesthetic can be used to predict response to neurolytic block (though caution, as some of the local anesthetic may be absorbed or provide placebo effect)
  • Typically performed with CT, US, or fluoroscopic guidance
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15
Q

Celiac plexus block - Indications

A

Visceral pain from:

  • Pancreatic cancer
  • Other upper abdominal tumours

That fails to respond to systemic opioid therapy. No clear survival benefit, but reduces opioid consumption and side effects

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16
Q

Celiac plexus block: Risks

A
  • Frail patients or those living far away may do better with overnight observation

Immediately following:

  • Diarrhea (typically transient, rarely necessitating PO opioid)
  • Orthostatic hypotension (typically transient, rarely necessitating PO ephedrine 30mg TID)

Catastrophic:

  • Paraplegia (rare occurrence) due to ischemic spinal cord injury from injury or spasm of the artery of Adamkiewicz
  • Aortic dissection
  • Generalised seizures
  • Circulatory arrest
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17
Q

Celiac plexus block: Results

A
  • Partial to complete pain relief in 90% of patients alive after 3 months
  • Results similar for pancreatic cancer and other abdominal malignancies
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18
Q

Lumbar sympathetic block: Indications

A

Injection through the anterior lateral aspect of the vertebral body on the same side as the painful extremity

  • Kidney pain (including phantom kidney pain)
  • Testicular pain
    Intractable lower extremity pain, including:
  • Inoperable PVD (most common)
  • Chronic painful leg ulceration
  • Complex regional pain syndrome
  • Phantom pain
  • Herpes zoster
  • Diabetic neuropathy
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19
Q

Lumbar sympathetic block: Results

A

PVD:

  • Increases cutaneous blood flow
  • Reduces rest pain
  • Enhances healing of chronic ischemic ulceration
  • 50-80% of patients experience partial or complete relief of pain at rest
  • Mean duration of relief is 6 months
20
Q

Lumbar sympathetic block: Risks

A

Lower morbidity, mortality, and cost compared to surgical sympathectomy

Complications are rare when radiographic imaging is used

21
Q

Stellate ganglion block: Indications

A

Innervates head, neck, upper extremties, and intrathoracic structures. Needle placed in anterior neck.

Cardiac

  • Angina
  • Inoperable CAD

Upper extremity pain:

  • Complex regional pain syndrome
  • PVD
  • Raynaud’s
  • Brachial plexus infiltration by tumour
  • Herpes zoster
  • Phantom Pain
22
Q

Stellate ganglion block: Results

A
  • Rarely indicated due to risk of complications (vascular injury or hemorrhage, esophageal or tracheal puncture, etc.)
  • Upper thoracic (T2-T3) paravertebral sympathectomy by surgery or radiofrequency ablation is preferred if cervicothoracic sympathectomy is needed
23
Q

MOA of sympathetic blockade

A
  • Visceral cancer pain reflects afferent input traveling with autonomic nerves (sympathatic or parasympathetic)
  • Nerve blocks interrupt these afferent fibers
  • Regional pain associated with focal autonomic dysfunction (vasomotor instability, swearing, etc.) may have a greater component of chronic regional pain syndrome with sympathetically mediated pain
24
Q

Superior hypogastric plexus block: Indications

A

Pelvic visceral pain from gynecological, colorectal, or GU cancer

Note that somatic pain will not improve

25
Q

Superior hypogastric plexus block: Results

A

Long-lasting relief in 70% of patients with positive response to diagnostic block

26
Q

Ganglion impar block: Indications

A

Intractable perineal pain

27
Q

Ganglion impar block: Results

A

Little evidence except for case series

28
Q

Neuraxial neurolysis: MOA

A
  • Chemical posterior rhizotomy (severing) or to interrupt pain signal transmission

Pain relief lasts for 6-12 months, complication rate from 1-14% which may be acceptable to some patients

29
Q

Neuraxial neurolysis: Indications

A

Restricted to:

  • Patients with advanced malignancy and pain restricted to a few dermatomes
  • Relatively localised chest wall or truck pain
  • Those who are non-ambulatory, incontinent with severe lower-extremity spasticity not relieved by systemic medications or spinal baclofen
30
Q

Neuraxial neurolysis: Complications

A
  • may result in derangements of the sensory, motor and autonomic systems to some degree (true sensory selectivity is rarely achieved)
  • inadequate pain relief
  • brief duration of effect
  • weakness of limb muscles and/or rectal/bladder sphincters
31
Q

Neuraxial neurolysis: Contraindications

A
  • Significant coagulopathy such as severe thrombocytopenia, disseminated intravascular coagulation (DIC)
  • Skin infection at the intended site of puncture

Relative contraindications include:

  • pain that is extensive and poorly localized,
  • pain felt to be primarily of neuropathic origin
32
Q

Spinal analgesics: Overview

A
  • Injection of analgesic drugs into either the epidural or subarachnoid space
  • Most common interventional pain therapy for patients with advanced malignancy whose pain cannot be controlled with systemic analgesics
  • Provides some patients with analgesia unattainable with systemic therapies, or comparable anasthesia with fewer side effects
33
Q

Spinal analgesics: Agents

A

Opioids

  • Morphine is most common, but others can be used
  • Delivers opioids close to the receptors in the dorsal horns of the spinal grey matter (both pre-synaptic - peripheral afferent nociceptor) and post-synaptic (second order spinal neuron)
  • Opioids bind and inhibit synaptic transmission between primary afferent nociceptors and second-order spinal neurons, and reduces firing of second-order neurons
  • If opioid alone is ineffective, combine with local anesthetics (bupivacaine, ropivicaine) or clonidine

Non-opioids: Anesthetics

  • Bupvicaine most common addition
  • Lidocaine and tetracaine avoided due to concerns re: neurotoxicity
  • Decrease nociceptive input and reduce sensitization of spinal cord neurons
  • Pain control without loss of sensory or motor function is most possible with EPIDURAL rather than subarachoid use
  • Use subarachnoid for non-ambulatory patients with refractory pain

Non-opioids: Clonidine

  • Alpha adrenergic agonist
  • Typically administered with an opioid or local anesthetic

Non-opioids: Baclofen

  • Subarachnoid infusion through an implanted pump used for patients with severe spasticity intolerant or unresponsive to systemic baclofen
  • Allows for higher CSF concentrations than attainable with PO administration
34
Q

Spinal Opioids: Adverse effects

A
  • Most commonly the same as with opioid therapy in general (e.g. constipation, drowsiness, nausea)
  • Incidence of effects not high with spinal administration as most patients have tolerance to prior systemic administration
  • If significant adverse effects occur, manage with small naloxone doses (often without reducing analgesia)

Respiratory depression

  • Respiratory depression is not common, but can occur at initiation or with dose increases
  • Watch for delayed respiratory depression (3-20 hrs later) that can occur with opioid migration within the CSF
35
Q

Spinal Clonidine: Advese effects

A
  • Hypotension
  • Bradycardia
  • Sedation

Dose-related and generally manageable

36
Q

Indications for spinal analgesics

A
  • Chronic cancer pain and non-cancer pain in populations with serious illness
  • Work best for deep, constant, somatic pain
  • Other pain (eg. cutaneous, intermittent somatic such as pathologic fracture, intermittent visceral from intestinal obstruction, and coexistant cancer and non-cancer pain) are variably responsive
  • Neuropathic pain MAY respond, but often requires different trials of drug combos
  • Trial with a temporary catheter before permanent spinal delivery system
37
Q

Contraindications to spinal analgesic therapy

A
  • Coagulopathy increases risk, withhold anticoagulants before implementing therapy
  • Septicemia (risk of spinal delivery system infection)
  • Local infection where there is no alternative for spinal catheter implantation

Not a contraindication:

  • Ongoing chemo or rads
  • Spinal mets (though insert away from mets to avoid trauma to a friable tumour mass or neural injury)
  • If CSF circulation may be blocked by an expanding tumour, place the catheter cephalad to the lesion
38
Q

Malfunction of spinal catheter systems

A
  • Signalled by abrupt or gradual worsening of pain (may be difficult to distinguish from disease progression)
  • Development of withdrawal
  • Use epidurography or myelograph to verify catheter location and patency
  • Use plain radiographs to verify structural integrity of spinal system
39
Q

Epidural catheter: Epidural fibrosis

A

Epidural fibrosis
- formation of scar tissue around the catheter in the epidural space)

Symptoms:

  • Back pain
  • Paresthesias on injection
  • Loss of analgesic effect
  • No signs of infection

Evaluation:
- Epidurographry

Management:
- Manage by repositioning the epidural catheter or replacing with a subarachnoid catheter

40
Q

Epidural catheter: Epidural infection or abscess

A

Symptoms:

  • Back and extremity pain
  • Weakness
  • Sensory abnormalities
  • Fever, leukocytosis

Prevention:
- Sterile technique

Evaluation:

  • Catheter aspirate for gram stain, culture
  • Spine MRI

Management:

  • Catheter aspiration for decompression
  • IV antibiotics
  • Remove the catheter
41
Q

Epidural or subarachnoid catheter: Cather dislodgement or disconnection, Pump malfunction

A

Symptoms:

  • Loss of analgesic effect
  • Opioid withdrawal

Prevention:

  • Implanted rather than percutaneous system, consider a subarachnoid catheter anchored to fascia to prevent dislodgment
  • Pump maintenence, low volume/low battery alarm for pump malfunction

Evaluation:

  • Plain radiographs with contrast injection via catheter for dislodgment
  • Pump analysis/mechanical support for pump malfunction

Management:
- Revise or replace catheter/pump

42
Q

Epidural or subarachnoid catheter: Infection at catheter insertion site

A

Symptoms:

  • Erythema
  • Tenderness at insertion point or incision site

Prevention:
Sterile technique appropriate catheter care

Evaluation:

  • Culture catheter exit site
  • Culture catheter aspirate

Treatment:

  • Antibiotics
  • Local site care
  • Remove catheter if no rapid improvement
43
Q

Subarachnoid catheter: Catheter-tip granuloma formation

A

Symptoms:

  • Cord compression
  • Loss of pain control
  • New back pain or radicular pain
  • Sensory abnormality
  • Weakness progression to paralysis
  • Especially in context of chronic opioid administration (may be related to activation of opioid receptors on inflammatory cells)

Prevention:
- Avoid excessive doses or concentrations of spinal opioids

Evaluation:
- Spine MRI or CT myelography

Treatment:

  • Surgical resection of granuloma if significant neuro deficit
  • Discontinuation of spinal analgesics may be followed by shrinkage and symptom improvement
44
Q

Subarachnoid catheter: Meningitis

A

Symptoms
- Meningeal irritation (severe headache, cervical stiffness, photophobia, fever)

Evaluation:
- Catheter aspirate of CSF for cell count, gram stain, glucose, culture

Prevention:

  • Sterile technique
  • Bacterial filters for pump refill or on percutaneous catheters

Management:

  • Systemic antibiotics, potentially subarachnoid antibiotics
  • Remove catheter system if no rapid improvement (call ID!)
45
Q

Percutaneous vertebroplasty and kyphoplasty: Procedure and indications

A

Vertebroplasty:
- Fractured vertebrae stabilised by injection of bone cement into the vertebral body marrow space

Kyphoplasty

  • Inflation of a high pressure balloon in the vertebral body to create a cavity, which is then filled with bone cement (may restore vertebral height)
  • May be preferred to conservative management in terms of pain, disability, quality of life, and decreased analgesic use

Indications:
- Osteoporotic vertebral compression fractures

Contraindications:

  • Spinal cord compression with clinical myelopathy
  • Overt spinal instability
  • Osteomyelitis
  • Epidural tumour spread
  • Posterior vertebral deficits

Palliative (71 decks)

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