Pain Management

SOURCE

Source: Herndon CM, Strickland JM, Ray JB. Pain management. In: DiPiro JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM, eds. Pharmacotherapy: A Pathophysiologic Approach. 10th ed. New York, NY: McGraw-Hill; 2017. http://accesspharmacy.mhmedical.com/content.aspx?bookid=1861&sectionid=146063604. Accessed January 23, 2017.

DEFINITION

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

ETIOLOGY

• Pain can occur from many causes, for example:

  • Surgery.

  • Trauma.

  • Labor.

  • Medical procedures.

  • Illnesses.

PATHOPHYSIOLOGY

• Nociceptive (adaptive) 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.

• Maladaptive (pathophysiologic) pain often described as chronic pain.

  • Neuropathic pain (eg, postherpetic neuralgia, diabetic neuropathy) results from nerve damage.

  • Maladaptive pain can be centralized, where no nerve injury or inflammation exists but a centrally mediated disturbance in pain processing within the CNS leads to pain hypersensitivity (eg, fibromyalgia, irritable bowel syndrome, tension-type headache).

• Acute pain (eg, surgery, trauma, labor, and medical procedures) usually is nociceptive.

• Chronic pain can be nociceptive, neuropathic, or centralized.

• Cancer pain includes both chronic and acute pain caused by the disease itself, treatment, or diagnostic procedures.

EPIDEMIOLOGY

• Greater than 100 million persons in the United States live with chronic pain.

• The economic burden of chronic pain exceeds 500 billion US dollars annually.

• 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.

CLINICAL PRESENTATION

• 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 (eg, sharp to dull, obvious to vague).

• Acute pain can cause:

  • Hypertension.

  • Tachycardia.

  • Diaphoresis.

  • Mydriasis.

  • Pallor.

  • These signs seldom present in chronic pain.

DIAGNOSIS

MEANS OF CONFIRMATION AND DIAGNOSIS

• Pain is subjective sensation; there are no specific laboratory tests for pain. Diagnosis based on:

  • Patient description.

  • History.

  • Physical exam.

• Pay attention to mental factors that may lower pain threshold, example:

  • Anxiety.

  • Depression.

  • Fatigue.

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