Chronic Pain
last authored: March 2011, David LaPierre
last reviewed:
Introduction
Chronic pain is defined as lasting more than three months, or beyond the time of tissue healing. Following changes in the central nervous system, chronic pain becomes a disease in itself.
Chronic pain is one of the most common causes of seeking care. There are incredible difficulties facing the clinician in regards to patients with chronic pain, and a great deal of empathy is required. Chronic pain can happen to anyone. Narcotic abuse has complicated treatment dramatically, but opiods can also be used to restore life to many patients.
Poorly managed chronic non-cancer pain can lead to substance abuse.
The Case of Billy Buresh
Billy is a 24 year-old man who was struck by a car while riding his bicycle four months ago. He was discharged from hospital after two days with fractures of his arm and leg. Since his injuries, he has been unable to work and is asking you, his family doctor, for increased doses of his oxycodone.
- how do you diagnose his pain?
- how do you approach his treatment, with medications and otherwise?
Causes and Risk Factors
Patients tend to fall within three main categories:
- those with known illness or trauma causing the pain
- those with no known precipitating causes
- those with psychiatric or psychological comibridities
There are many causes and risk factors of chronic pain.
Trauma can include motor vehicle collisions, work-related injury, sporks injury, repetitive motion injury, and falls.
Surgical pain: back surgery, incisional pain, phantom limb pain, post-thoracotomy syndrome
Medical conditions:
- arthritis
- lumbar stenosis, fibromyalgia, cancer, diabetic neuropathy, multiple sclerosis, shingles, HIV, previous chemotherapy, stroke, spinal cord injury
Low back pain
FM
headache
post-herpetic neuralgia
diabetic neuropathy
Psychiatric conditions: anxiety, depression, borderline personality disorder, PTSD, schizoaffective disorders, survivors of sexual abuse
Idiopathic
Secondary gain: narcotic abuse; Munchhausen syndrome
- spontaneous pain
- allodynia - pain in response to touch
- hyperalgesia - enhanced pain in response to noxious stimuli
predisposition
early stress
sex hormones
cognitive factors
depression
aging
decreased DNIC control
Pathophysiology
Chronic pain is a complex condition. As tissue damage or inflammation is intense, repetitive, or extended, afferent fibres display increased firing with a decreased threshold. This can occur in a number of ways:
- increased expression of receptors and sodium channels
- phenotype switch from A-fibres to C-fibres
- involvement of sympathetic nervous system, with NE inducing sensory impulses
- central sensitization in the dorsal horn
- the synapse becomes transformed, with changes in NMDA and neurokinin levels
- allows Aβ stimuli to be perceived as pain
There is also a large influence of psychosocial, cultural, and learned beliefs, emotions, and behaviours in regards to chronic pain.
Chronic pain may be divided into three categories:
- nociceptive pain may be somatic or visceral.
- neuropathic pain
- sympathetically-maintained pain: injury to peripheral nerves can cause severe burning pain, swelling, changes in sweat production.
"Hardware is fine, but the software is now different. We need to reprogram the software".
Signs and Symptoms
Approach chronic pain with the belief that the patient is being honest.
It is important to understand whether the pain is neuropathic vs nociceptive, or both.
- history
- validated tools
- physical exam
History
A helpful acronym is often used for understanding pain:
Onset
Provoking/palliating factors
Quality (burning, stabbing, throbbing)
Radiation
Severity (Visual Analog Scale)
Timing: onset, duration, course, daily variation
Seek to understand how the pain is affecting the person's life - their job, home, and relationships
Past medical history is important, and includes:
- trauma
- arthritis
- surgeries
- cancer
- psychiatric illness
- past or current abuse
- substance abuse
Assess to identify psychiatric, addiction, or personality disorders that could be contributing to the chronic pain and hindering it's effective treatment. Borderline personality disorder (BPD) is seen in up to 30% of patients with chronic pain, making it an important consideration (Sansone and Sansone, 2012).
Validated Tools
There are a number of validated tools that can be used. These include:
Brief Pain Inventory
Body Pain Diagram
DN4 - useful for neuropathic pain
It is important to assess for risk of abuse. The main tool used here is the Opioid Risk Tool.
Physical Exam
For patients who are non-verbal, observe facial expression, changes in behaviour, vocalization, and movements.
Begin by assessing how th patient stands, walks, and moves.
Musculoskeletal: should include joint(s) affected, including inspection, palpation, range of motion, power, and special tests
Neurological: strength, sensation, reflexes, sensory, vibration, and deep palpation of trigger points
Skin: changes in colour, temperature, moisture, hair growth (for complex regional pain syndrome)
Investigations
- lab investigations
- diagnostic imaging
Lab Investigations
Lab investigations can be helpful in understanding the cause or provoking factors in chronic pain. These include:
- CBC
- ESR
- toxicology
- liver function tests, amylase lipase (if pain is abdominal)
- rheumatoid factor, ANA, ?serology for Lyme disease and gonorrhea (if paint is in joints)
If you are treating pain with opioids, order random drug screens with qualitative and quantitative analysis. Include urinalysis to ensure the sample is indeed urine.
Diagnostic Imaging
Imaging should include plain films, ultrasound, CT, and/or MRI of the affected area(s).
EMG can also be helpful in determining neurological involvement.
Prevention
It is important to endeavour to prevent the development of chronic pain through a number of strategies. Pre-emptive strategies are important to prevent neuroplasticity from occurring in situations where chronic pain is a possibility
Work and sports-related injury can be mitigated through safety equipment, proper ergonomic design, and strengthening exercises. Acute pain should be quickly evaluated, and rehabilitation should be offered as appropriate.
The varicella vaccine can prevent shingles, and rapid treatment with antivirals can prevent post-herpetic neuralgia.
Diabetic control can prevent neuropathy.
Treatments
The goals of treatment of chronic pain are to:
- improve function
- improve quality of life
- minimize risk, to the health care provider, patient, and society
- decrease pain
Set SMART goals for treatment.
Treatment is most effective when multi-pronged. Treat the causes as much as possible. It is critical to build trust between provider and patient. Maintain clear boundaries, including call frequency and behaviour towards staff. A team-approach can be very helpful, including the physician, counselor, physiotherapist, occupational therapist, socual worker, addictions therapist, and spiritual counselor.
For all patients, keep a pain diary to understand provoking or palliating factors, as well as need for pain medication.
All patients on chronic opioid therapy should have a pain contract, undergo random urine screening, and have a zero tolerance understanding if diversion is identified.
It is important to have only one prescriber, to not offer early refills, and police involvement as required.
- medications
- adjuvants
- non-pharmacologic modalities
Medications
dlp: have a map of periphery, SC, brain stem, midbrain, cortex with actions of different classes.
It is beneficial to trial medications one at a time, starting at a low dose and gradually increasing until effect, maximum dosage, or intolerable side effects. Frame efforts as 'trials' or 'tests' of the drug.
Acetaminophen: do not exceed 4 grams daily in adults, or 2 grams daily in seniors or those with liver disease/alcohol abuse.
NSAIDs: be cautious with gastric and cardiovascular side effects.
Opioids
Low-strength opioids: codeine, hydrocodone, tramadol.
Methadone
Buprenorphine is a mixed opioid agonist and antagonist; it can be used for both chronic pain and substance abuse.
Once a target dose is reached, use a sustained-release formulation, with short-acting only as breakthrough.
For patients with chronic, non-cancer pain who are addicted to opioids, three treatment options are offered:
- methadone or buprenorphine
- structured opioid
- abstinence-based treatments
Adjuvants
Adjuvants may be used for pain. However, first optimize the opioid dose, and avoid polypharmacy if possible.
Tricyclic antidepressants such as amitriptyline and nortriptyline benefit moderate pain relief independent of effect on mood
- inhibits NA/5-HT reuptake, strengthening descending inhibition
- blocks NMDA receptors
SSRIs and SNRIs such as venlafaxine, duloxetine are also effective.
Anticonvulsants act by binding Ca2+ channel, perhaps on sensory neurons. They have partial efficacy: NNT 5; NNH 25.
Anticonvulsants include:
- gabapentin
- pregabalin
- carbamazapine
- phenytoin
antiarrythmics
capsaicin
cannabinoids
steroids
Massage
cold, heat
TENS
trigger points
relaxation, cognitive strategy (increased descending inhibition)
Consequences and Course
Complications of chronic pain nclude:
- substance abuse and addiction
- physical dependence and tolerance
- diversion
Resources and References
Sansone RA, Sansone LA. 2012. Chronic pain syndromes and borderline personality. Innov Clin Neurosci. 9(1):10-4.
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