Chapter 6: Pain and Its Management

Approach to the patient: Pain

Pain is the most common symptom that brings a pt to a physician’s attention. Management depends on determining its cause, alleviating triggering and potentiating factors, and providing rapid and effective pain relief whenever possible. Pain may be of somatic (skin, joints, muscles), visceral, or neuropathic (injury to nerves, spinal cord pathways, or thalamus) origin. Characteristics of each are summarized in Table 6-1.

Neuropathic Pain

Due to damage of peripheral or central nociceptive pathways. Definitions: neuralgia: pain in the distribution of a single nerve, as in trigeminal neuralgia; dysesthesia: spontaneous, unpleasant, abnormal sensation; hyperalgesia and hyperesthesia: exaggerated responses to nociceptive or touch stimulus, respectively; allodynia: perception of light mechanical stimuli as painful, as when vibration evokes painful sensation. Reduced pain perception is called hypalgesia or, when absent, analgesia. Causalgia is continuous severe burning pain with indistinct boundaries and accompanying sympathetic nervous system dysfunction (sweating; vascular, skin, and hair changes—sympathetic dystrophy) that occurs after injury to a peripheral nerve.

Sensitization refers to a lowered threshold for activating primary nociceptors following repeated stimulation in damaged or inflamed tissues; inflammatory mediators play a role. Sensitization contributes to tenderness, soreness, and hyperalgesia (as in sunburn).

Referred pain results from the convergence of sensory inputs from skin and viscera on single spinal neurons that transmit pain signals to the brain. Because of this convergence, input from deep structures is mislocalized to a region of skin innervated by the same spinal segment.

Chronic Pain

The problem is often difficult to diagnose with certainty, and pts may appear emotionally distraught. Several factors can cause, perpetuate, or exacerbate chronic pain: (1) painful disease for which there is no cure (e.g., arthritis, cancer, chronic daily headaches, diabetic neuropathy); (2) perpetuating factors initiated by a bodily disease that persist after the disease has resolved (e.g., damaged sensory or sympathetic nerves); (3) psychological conditions. Pay special attention to the medical history and to depression. Major depression is common, treatable, and potentially fatal (suicide).


TABLE 6-1: Characteristics of Somatic and Neuropathic Pain

Somatic pain

 Nociceptive stimulus usually evident

 Usually well localized

 Similar to other somatic pains in pt’s experience

 Relieved by anti-inflammatory or narcotic analgesics

Visceral pain

 Most commonly activated by inflammation

 Pain poorly localized and usually referred

 Associated with diffuse discomfort, e.g., nausea, bloating

 Relieved by narcotic analgesics

Neuropathic pain

 No obvious nociceptive stimulus

 Associated evidence of nerve damage, e.g., sensory impairment, weakness

 Unusual, dissimilar from somatic pain, often shooting or electrical quality

 Only partially relieved by narcotic analgesics; may respond to antidepressants or anticonvulsants

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