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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§ionid=146063604. Accessed January 23, 2017.
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Pain is an unpleasant, subjective, sensory, and emotional experience associated with actual or potential tissue damage or described in terms of such damage.
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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.
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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.
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CLINICAL PRESENTATION
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Acute pain may be:
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:
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MEANS OF CONFIRMATION AND DIAGNOSIS
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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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