> Table of Contents > Chronic Pain Management: An Evidence-Based Approach
Chronic Pain Management: An Evidence-Based Approach
Jennifer Reidy, MD, MS, FAAHPM
image BASICS
  • Chronic pain is pain persisting beyond the time of normal tissue healing, usually >3 months.
  • Over time, neuroplastic changes in the CNS transform pain into a chronic disease itself. Pain levels can exceed observed pathology on exam or imaging.
  • Pain experience is inherently related to emotional, psychological, and cognitive factors.
  • An epidemic of undertreated pain coexists with an epidemic of prescription drug abuse in the United States.
  • Use a system-based practice to safely and effectively prescribe opioids when indicated for chronic nonmalignant pain.
EPIDEMIOLOGY
Incidence
Incidence is rising, but exact rate is unclear. The annual economic cost of chronic pain in the United States is estimated at $560 to $635 billion (1)[B].
Prevalence
In the United States, an estimated 100 million adults live with chronic pain—more than the total affected by heart disease, cancer, and diabetes combined (1)[B].
Chronic pain accounts for 20% of outpatient visits and 12% of all prescriptions (2)[B].
ETIOLOGY AND PATHOPHYSIOLOGY
  • With intense, repeated, or prolonged stimulation of damaged or inflamed tissues, the threshold for activating primary afferent pain fibers is lowered, the frequency of firing is higher, and there is increased response to noxious and/or normal stimuli (peripheral and central sensitization). The amygdala, prefrontal cortex, and cortex are thought to relay emotions and thoughts that create the pain experience, and these areas may undergo structural and functional changes with chronic pain.
  • Many patients have an identifiable etiology (most commonly musculoskeletal problems or headache), but pain levels can be worse than observable tissue injury. A significant percentage of patients have no obvious cause of chronic pain.
Genetics
Current research suggests genetic polymorphism in opioid receptors, which may affect patient's response and/or side effects to individual opioids.
RISK FACTORS
  • Traumatic: motor vehicle accidents, repetitive motion injuries, sports injuries, work-related injuries, and falls
  • Postsurgical: any surgery but especially back surgeries, amputations, and thoracotomies
  • Medical conditions: See “Commonly Associated Conditions” later.
  • Psychiatric comorbidities: substance abuse, depression, posttraumatic stress disorder (PTSD), personality disorders
  • Aging: increased incidence with age but should not be considered a “normal” part of aging
GENERAL PREVENTION
  • Avoidance of work-related injuries through the use of ergonomically correct workplace design
  • Exercise and physical therapy to help prevent work-related low back pain
  • Varicella vaccine and rapid treatment of shingles to lower risk of postherpetic neuralgia
  • Tight glycemic control for diabetic patients, alcohol cessation for alcoholics, smoking cessation
COMMONLY ASSOCIATED CONDITIONS
Any chronic disease and/or its treatment can cause chronic pain, including diabetes, cardiovascular disease, HIV, progressive neurologic conditions, lung disease, cirrhosis, autoimmune disease, cancer, renal failure, depression, and mental illness.
image DIAGNOSIS
Chronic pain can be divided into two general categories:
  • Nociceptive pain (two types)
    • Somatic: skin, bone, soft tissue disease; described as well-localized, sharp, stabbing, aching
    • Visceral: visceral inflammation/injury; described as poorly localized, dull, aching; may refer to sites remote from lesion
  • Neuropathic_pain: damaged peripheral or central nerves; described as burning, tingling, and/or numbness
    • Sympathetically mediated pain: Peripheral nerve injury can cause severe burning pain, swelling of the affected limb, and focal changes in sweat production and skin appearance. Example: complex regional pain syndrome
PHYSICAL EXAM
Exam is guided by history and must include functional and mental assessments.
DIFFERENTIAL DIAGNOSIS
  • The causes of pain are numerous, and clinic presentations are protean, depending on the individual patient.
  • There is a spectrum of aberrant drug-taking behaviors, and differential diagnosis includes
    • Inadequate analgesia (“pseudoaddiction”), disease progression, opioid-resistant pain, opioid-induced hyperalgesia, addiction, opioid tolerance, self-medication of nonpain symptoms, criminal intent (diversion)
DIAGNOSTIC TESTS & INTERPRETATION
Testing is based on differential diagnosis of pain syndrome to elucidate etiology.
Initial Tests (lab, imaging)
  • Urine drug screen: Order qualitative analysis for drugs of abuse and quantitative analysis for the drug you are prescribing.
  • Most tests are immunoassays, which usually detect morphine and heroin but often not other opioids. Laboratory-based chromatography/spectrometry can identify specific drugs. Clinicians should be aware of uses and limitations of local laboratory testing (http://www.aafp.org/afp/2010/0301/p635.html).
Follow-Up Tests & Special Considerations
If patient is taking chronic opioid therapy, order random urine drug screens as part of the “universal precautions” approach (see “Ongoing Care”).
Diagnostic Procedures/Other
  • Consider interventional pain clinic for complicated joint injections and nerve root blocks, which can be diagnostic.
  • If complex regional pain syndrome is suspected, a sympathetic block can be diagnostic and possibly prevent chronic pain.
image TREATMENT
  • Goals of treatment are restoring function and a decrease in pain while balancing risks and benefits of therapies.
  • Intradisciplinary teams offer most effective approach to chronic pain, including its physical, emotional, and psychological aspects. These teams may include the patient, family, primary care doctor, nurse, pain management specialist, pharmacist, psychologist, psychiatrist, physical and occupational therapists, physiatrist, complementary medicine practitioners, social worker, and (if needed) addiction medicine specialist (3)[B].
  • Treatment should always include nonpharmacologic therapies such as exercise, cognitive-behavioral therapy (CBT), patient and family education, yoga, massage, relaxation techniques, support groups, meditation, and acupuncture.
GENERAL MEASURES
Keep a pain and function diary to record pain and activity level and how much medication is taken.
MEDICATION
  • Always begin with exercise, physical therapy, CBT, and self-management skills before or with pain medications. Use sequential time-limited trials of medications, starting at low doses, and gradually increasing until either effect or dose-limiting side effects are reached. Rational polypharmacy may be indicated (such as an opioid + neuropathic agent).
  • For mild to moderate chronic pain
    • Acetaminophen: daily dose not to exceed total 4 g in healthy adults and 2 g in the elderly or those with hepatic disease or active or past history of alcohol use
    • NSAIDs: COX-2 selective inhibitors should be used with caution because of cardiac risks but may have less gastric risk. If high cardiac risk consider nonselective COX inhibitor (such as naproxen) with or without gastric prophylaxis (depending on ulcer risk).
    • P.203

    • “Weak” opioids, including tramadol. Caution: Opioid analgesic combinations can lead to serious acetaminophen or NSAID toxicities if patients exceed safely prescribed doses.
    • Topical agents: NSAIDs, lidocaine (gel is less expensive than patch), ketamine, capsaicin
  • For neuropathic pain
    • Classes of medications include (i) tricyclic antidepressants (desipramine and nortriptyline have fewer side effects); (ii) serotonin-norepinephrine reuptake inhibitor (SNRI) antidepressants (duloxetine); (iii) anticonvulsants (alpha 2-delta ligands, gabapentin, and pregabalin); (iv) opioids, including tramadol. Example: combination of nortriptyline + gabapentin
    • See “Neuropathic Pain.”
  • For moderate to severe chronic pain
    • Strong opioids, including morphine, oxycodone, hydromorphone, oxymorphone, fentanyl. Check opioid equianalgesic tables for dosing by route of administration.
    • No evidence supports any of these strong opioids as superior or having improved side effect profile.
    • In patients with chronic back pain, opioids may be efficacious for short-term use, but long-term benefits and side effects are unclear; in addition, aberrant medication-taking behaviors range from 5% to 24%.
      • Morphine should be avoided in patients with significant renal insufficiency.
      • Methadone should only be prescribed by experienced providers. The only opioid that also acts as N-methyl-D-aspartate receptor antagonist, methadone has many drug interactions and can contribute to potentially fatal cardiac arrhythmias.
    • Once stable dose of opioids is established, change to sustained-release formulations if pain is constant or very frequent. Short-acting formulations are only for breakthrough or episodic pain.
    • Common side effects: constipation: Senna should be prescribed at time opioids are started; also nausea, sedation, mental status changes, and pruritus
SURGERY/OTHER PROCEDURES
Consider interventional procedures, including joint injections, nerve blocks, spinal cord stimulation, and intrathecal medication among others, as needed.
COMPLEMENTARY & ALTERNATIVE MEDICINE
  • Acupuncture: efficacy in chronic neck and back pain and fibromyalgia
  • Exercise: efficacy in low back pain and fibromyalgia
  • Improved mood and coping skills, decreased disability with CBT
  • Mind-body interventions: yoga, tai chi, hypnosis, progressive muscle relaxation, meditation
image ONGOING CARE
FOLLOW-UP RECOMMENDATIONS
Patient Monitoring
  • It can be difficult to identify appropriate pain relief-seeking behavior from inappropriate drug-seeking, but consistent patient-clinician relationships over time can often discern the difference.
  • Always maintain a risk-benefit stance and avoid judging a patient.
  • Assess and document benefits, pain levels, functioning, and quality of life. In general, patients successfully taking opioids for pain become more engaged (better relationships and productive work).
  • At each visit, assess and document harm, using universal precautions approach. This system-based practice includes the following:
    • Informed consent for opioid therapy
    • Written or electronic agreement between patient and clinician
    • One prescribing clinician (or designee) and one pharmacy
    • No after-hours prescriptions or early refills
    • Mandatory police reports for medication thefts
    • Random urine drug tests, pill/patch counts
    • Requirements for patient to continue with physical therapy, counseling, psychiatric medications, or other necessary treatments
    • Participate in state's prescription drug monitoring program: See www.pmpalliance.org.
    • Taper and discontinue medications (10% dose reduction per week) if patient does not benefit, if side effects outweigh benefits, or if medications are abused or diverted. If addiction is suspected, always offer treatment for substance abuse (4,5)[B].
PATIENT EDUCATION
American Chronic Pain Association: http://theacpa.org/
REFERENCES
1. Institute of Medicine, Committee on Advancing Pain Research, Care, and Education. Relieving Pain in America: A Blueprint for Transforming Prevention, Care, Education and Research. Washington, DC: The National Academies Press; 2011.
2. Alford DP, Krebs EE, Chen IA, et al. Update in pain medicine. J Gen Intern Med. 2010;25(11): 1222-1226.
3. Dobscha SK, Corson K, Perrin NA, et al. Collaborative care for chronic pain in primary care: a cluster randomized trial. JAMA. 2009;301(12): 1242-1252.
4. American Society of Anesthesiologists Task Force on Chronic Pain Management. Practice guidelines for chronic pain management: an updated report by the American Society of Anesthesiologists Task Force on Chronic Pain Management and the American Society of Regional Anesthesia and Pain Medicine. Anesthesiology. 2010;112(4):810-833.
5. Manchikanti L, Abdi S, Atluri S, et al. American Society of Interventional Pain Physicians (ASIPP) guidelines for responsible opiod prescribing in chronic non-cancer pain: Part 2—guidance. Pain Physician. 2012;15(3 Suppl):S67-S116.
6. Bohnert AS, Valenstein M, Bair MJ, et al. Association between opioid prescribing patterns and opioid overdose-related deaths. JAMA. 2011;305(13):1315-1321.
Additional Reading
&NA;
  • Federation of State Medical Boards of the United States, Inc. Model policy for the use of controlled substances for the treatment of pain www.painpolicy.wisc.edu/sites/www.painpolicy.wisc.edu/files/model04.pdf.
  • Washington State Agency Medical Director's Group. Interagency guideline on opioid dosing for chronic non-cancer pain: an educational aid to improve care and safety with opioid therapy. www.agencymeddirectors.wa.gov.
Codes
&NA;
ICD10
  • G89.29 Other chronic pain
  • G89.21 Chronic pain due to trauma
  • G89.28 Other chronic postprocedural pain
Clinical Pearls
&NA;
  • Start with the presumption that the patient's pain is real, even if pathophysiologic evidence for it cannot be found.
  • Emphasize that being pain-free may not be possible but that better function and quality of life can be shared goals.
  • Use a multidisciplinary approach with nonpharmacologic therapies, exercise, patient self-management strategies and thoughtful medication use with clear goals, expectations, and documentation of care plan.
  • Use universal precautions and systems-based practice to safely and effectively prescribe opioids for chronic pain.