Interventional Approaches for Pain Flashcards
Prevalence of inadequate pain control in advance cancer
10-30%
Indications for interventional pain control
- Uncontrolled pain despite adequate systemic analgesics
- Unacceptable systemic analgesics adverse effects
Characteristics increasing the likelihood of needing procedural pain therapy
Neuropathic pain
Somatic pain that is sharp and severe
Pain that fluctuates markedly
Significant side effects with medication
Trigger point injections - indications
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
Trigger point injection - process
- Consider physical therapy alone, or other alternative txs (dry needling, acupuncture, pulse radiofrequency, botox)
- Local anesthetic injected into the trigger point
Intra-articular injections: Indications and risks
- May be used in arthritis or joint-related pain
- Most commonly, corticosteroids
Side effects:
- Infection
- Bleeding
- Nerve injury
- Joint destruction
Botox injections - mechanism of action
- 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
Botox: Indications
- Spasticity and movement disorders
Poorer evidence for:
- Migraines
- Interstitial cystitis
- Chronic myofascial pain
Botox - risks and effectiveness
- 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
Peripheral nerve blocks - indications
- 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
Risks of peripheral nerve blocks
Long-term catheters:
- Infection
- Local anesthetic toxicity
- Catheter displacement
- Technical difficulties (catheter knotting)
Neurolytic blocks - agents used
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
Radiofrequency neurotomy
- 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)
Sympathetic nervous system block
- 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
Celiac plexus block - Indications
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
Celiac plexus block: Risks
- 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
Celiac plexus block: Results
- Partial to complete pain relief in 90% of patients alive after 3 months
- Results similar for pancreatic cancer and other abdominal malignancies
Lumbar sympathetic block: Indications
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
Lumbar sympathetic block: Results
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
Lumbar sympathetic block: Risks
Lower morbidity, mortality, and cost compared to surgical sympathectomy
Complications are rare when radiographic imaging is used
Stellate ganglion block: Indications
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
Stellate ganglion block: Results
- 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
MOA of sympathetic blockade
- 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
Superior hypogastric plexus block: Indications
Pelvic visceral pain from gynecological, colorectal, or GU cancer
Note that somatic pain will not improve
Superior hypogastric plexus block: Results
Long-lasting relief in 70% of patients with positive response to diagnostic block
Ganglion impar block: Indications
Intractable perineal pain
Ganglion impar block: Results
Little evidence except for case series
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
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
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
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
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
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
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
Spinal Clonidine: Advese effects
- Hypotension
- Bradycardia
- Sedation
Dose-related and generally manageable
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
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
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
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
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
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
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
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
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!)
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
