Chronic Pain Management: An Evidence-Based Approach

Jennifer Reidy, MD, MS, FAAHPM

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

HISTORY

• Obtain pain history: location, onset, intensity, duration, quality, temporal pattern, exacerbating agents, alleviators, prior treatments
• Assess and document how pain affects patient’s functioning and quality of life and what they expect from treatment.
• Screen for personal or family history of substance abuse (including tobacco addiction), mental health conditions, domestic violence, or sexual abuse.
• Use standardized tools: pain severity—Brief Pain Inventory (short form); mood—Patient Health Questionnaire-9 (PHQ-9); substance abuse—Screener and Opioid Assessment for Patients with Pain (SOAPP), multiple versions
• Use screening to risk stratify patients for risks of chronic opioid therapy and increased monitoring; a positive screen does not automatically exclude patients from opioid therapy.

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.