Interventional Approaches for Pain Flashcards
1
Q
Prevalence of inadequate pain control in advance cancer
A
10-30%
2
Q
Indications for interventional pain control
A
- Uncontrolled pain despite adequate systemic analgesics
- Unacceptable systemic analgesics adverse effects
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
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
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
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
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
8
Q
Botox: Indications
A
- Spasticity and movement disorders
Poorer evidence for:
- Migraines
- Interstitial cystitis
- Chronic myofascial pain
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
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
11
Q
Risks of peripheral nerve blocks
A
Long-term catheters:
- Infection
- Local anesthetic toxicity
- Catheter displacement
- Technical difficulties (catheter knotting)
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
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)
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
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
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
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
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
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
Superior hypogastric plexus block: Results
Long-lasting relief in 70% of patients with positive response to diagnostic block
26
Ganglion impar block: Indications
Intractable perineal pain
27
Ganglion impar block: Results
Little evidence except for case series
28
Neuraxial neurolysis: MOA
- 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
Neuraxial neurolysis: Indications
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
Neuraxial neurolysis: Complications
- 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
Neuraxial neurolysis: Contraindications
- 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
Spinal analgesics: Overview
- 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
Spinal analgesics: Agents
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
Spinal Opioids: Adverse effects
- 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
Spinal Clonidine: Advese effects
- Hypotension
- Bradycardia
- Sedation
Dose-related and generally manageable
36
Indications for spinal analgesics
- 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
Contraindications to spinal analgesic therapy
- 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
Malfunction of spinal catheter systems
- 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
Epidural catheter: Epidural fibrosis
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
Epidural catheter: Epidural infection or abscess
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
Epidural or subarachnoid catheter: Cather dislodgement or disconnection, Pump malfunction
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
Epidural or subarachnoid catheter: Infection at catheter insertion site
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
Subarachnoid catheter: Catheter-tip granuloma formation
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
Subarachnoid catheter: Meningitis
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
Percutaneous vertebroplasty and kyphoplasty: Procedure and indications
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
