Pain Management

Source: Baumann TJ, Strickland JM, Herndon DM. Pain Management. In: DiPiro JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM, eds. Pharmacotherapy: A Pathophysiologic Approach. 8th ed. http://accesspharmacy.com/content.aspx?aid=7986332. Accessed June 20, 2012.

• Pain is an unpleasant, subjective, sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage.

• Pain can occur from many causes, for example:
  • Surgery
  • Trauma
  • Labor
  • Medical procedures
  • Illnesses

• Nociceptive (acute) pain is somatic (from skin, bone, joint, muscle, or connective tissue) or visceral (from internal organs).
  • Free nerve endings known as nociceptors can be stimulated by mechanical, thermal, and chemical impulses.
    • Action potentials transmitted along afferent nerve fibers to spinal cord and then ascend to higher centers.
    • The thalamus may act as relay station and pass impulses to central structures, where pain is processed further.
  • Body modulates pain through several processes, including endogenous opioid system.
• Neuropathic and functional pain often described as chronic pain.
  • Neuropathic pain (e.g., postherpetic neuralgia, diabetic neuropathy) results from nerve damage.
  • Functional pain (e.g., fibromyalgia, irritable bowel syndrome, tension-type headache) involves abnormalities in nervous system.
• Acute pain (e.g., surgery, trauma, labor, and medical procedures) usually is nociceptive, but can be neuropathic.
• Chronic pain can be nociceptive, neuropathic/functional, or both.

• In a survey, 1 in 4 Americans reported pain that lasted for >24 hours in previous month; in those reporting pain, 42% stated that it lasted >1 year.
• 76.5 million Americans report they are in chronic pain.
• Each year, 25 million Americans experience acute pain due to injury or surgery, and one-third of Americans experience severe chronic pain at some point in their lives.

• Patients may be in obvious acute distress or appear to have no noticeable suffering.

Signs and Symptoms

• Acute pain may be:
  • Sharp or dull
  • Burning
  • Shock-like
  • Tingling
  • Shooting
  • Radiating
  • Fluctuating in intensity
  • Varying in location
  • Occurring in timely relationship with obvious noxious stimulus
• Chronic pain can present similarly and often occurs without time relationship to noxious stimulus.
• Over time, chronic pain presentation may change (e.g., sharp to dull, obvious to vague).
• Acute pain can cause:
  • Hypertension
  • Tachycardia
  • Diaphoresis
  • Mydriasis
  • Pallor
  • These signs seldom present in chronic pain.
• Neuropathic pain often chronic, not well described, and not easily treated with conventional analgesics.

Means of Confirmation and Diagnosis

• Pain is subjective sensation; diagnosis based on:
  • Patient description
  • History
  • Physical exam
• Baseline pain description can be obtained by assessing PQRST characteristics:
  • Precipitating factors
  • Quality
  • Radiation
  • Severity
  • Temporal factors
• Pay attention to mental factors that may lower pain threshold, example:
  • Anxiety
  • Depression
  • Fatigue
  • Anger
  • Fear
• Behavioral, cognitive, social, and cultural factors may also affect pain experience.

Laboratory Tests

• Perform individual tests as required to identify potential underlying causes.

Imaging

• Performed as required to identify underlying causes.

Diagnostic Procedures

• Performed as required to identify underlying causes.

Differential Diagnosis

• Somatoform disorders
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