Chronic Pain Management: An Evidence-Based Approach

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Basics

  • Chronic pain is typically defined as pain persisting beyond the time anticipated for normal tissue healing, usually >3 months.
  • Over time, neuroplastic changes in the CNS transform pain into a chronic disease. Pain levels typically exceed the pathology observed 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 an evidence-based, systems-based practice to safely and effectively prescribe opioid medications only 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).

Prevalence
In the United States, an estimated 50 million adults live with chronic pain. Individuals reporting severe pain are more likely to have impaired health status, use more health care, and suffer more disability (1).

ALERT
Caution: Opioid-related overdoses are at an all-time high. From 2000 to 2016, over half a million people died from drug overdoses (http://www.cdc.gov/drugoverdose/index.html).

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 relay emotions related to the pain experience, and these areas undergo structural and functional changes over time.
  • Patients often have an identifiable etiology (most commonly musculoskeletal problems or headache), but pain levels are often worse than observable tissue injury. Many patients have no obvious source of chronic pain.

Genetics
Current research suggests a genetic polymorphism in opioid receptors; 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: especially back surgeries, amputations, and thoracotomies
  • 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

  • Prevent work-related injuries through the use of ergonomic workplace design.
  • Exercise and physical therapy 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, prevention of alcohol abuse, 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.

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