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Pain Health Article

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Causes and symptoms

Pain is the most common symptom of injury and disease, and descriptions can range in intensity from a dull ache to sharp, knifelike or burning pain. Nociceptors have the ability to convey information to the brain that indicates the location, nature, and intensity of the pain. For example, stepping on a nail sends an information-packed message to the brain; the foot has experienced a puncture wound that hurts a lot, at which point (almost simultaneously) the message goes back to the foot and leg to move or change placement immediately, to get away from the stimulus (nail). This has been termed a "knee-jerk reaction."

Pain perception also varies depending on the location of the pain. The kinds of stimuli that cause a pain response on the skin include pricking, cutting, crushing, burning, scraping (skin layers removed), and freezing. These same stimuli would not generate much of a response in the intestine. Intestinal pain arises from stimuli such as swelling, inflammation, distension, and diminished blood supply (tissue hypoxia).

Diagnosis

The assessment of pain is subjective and is weighed in relation to other symptoms and individual experiences when trying to determine the source of the pain. An observable injury, such as a broken bone, may be a clear indicator of the type of pain a person is suffering. Determining the specific cause of internal pain is more difficult. Other symptoms, such as fever or nausea, help to refine and focus attention to more specific possibilities. In some cases, such as lower-back pain, a specific cause may not be identifiable without image assessment, such as by x ray or CT scan. Diagnosis of the disease or disorder causing a specific pain is further complicated by the fact that pain can be referred, manifesting farther along the pathway than the origin might suggest. For example, pain arising from fluid accumulating at the base of the lung may be referred, with the patient experiencing pain in the shoulder area. In addition, there is the pain (usually muscular) that results from "guarding" against the original pain source. For instance, a rotator-cuff shoulder injury causes acute pain, but it may be associated with muscular pain of the neck and upper back, the result of the body's attempt to either protect itself or get away from sharp pain.

Since pain is a subjective experience, it may be very difficult for the patient to communicate its exact quality and intensity to the nurse or doctor. There are no diagnostic tests that can determine the quality or intensity of an individual's pain. Therefore, a medical examination will include many questions about where the pain is located, its intensity, and its nature (type of pain). Questions are also directed to determining the things that increase or relieve the pain, how long the pain has lasted, and whether there are any variations in it. An individual may be asked to use a pain scale to describe the pain. One such scale assigns a number to the pain intensity; for example, 0 may indicate no pain, and 10 may indicate the worst pain the person has ever experienced. Scales are modified by using faces for infants and children to accommodate their level of comprehension.

Treatment

There are many drugs aimed at preventing or treating pain. Nonopioid analgesics, narcotic analgesics, anticonvulsant drugs, and tricyclic antidepressants work by blocking the production, release, or uptake of selected neurotransmitters. Drugs from different classifications may be combined to alleviate specific types of pain.

Nonopioid analgesics include common over-thecounter medications such as aspirin, acetaminophen (Tylenol), and ibuprofen (Advil). These are most often used for minor pain, but there are some prescription-strength medications in this classification. These drugs are called nonsteroidal anti-inflammatory drugs (NSAIDS) and relieve pain by reducing inflation.

Narcotic analgesics are available legally only with a prescription and are used for the relief of severe pain, such as postoperative pain from major surgery, or cancer pain. These drugs include codeine, morphine, meperidine, and methadone. Contrary to earlier beliefs, addiction to these medications is not common; people who genuinely need these drugs for pain control typically do not become addicted, because the drugs are usually given for only a short period of time, with the exception of cancer-pain relief.

Anticonvulsants as well as antidepressant drugs were initially developed to treat seizures and depression, respectively. However, it was discovered that these drugs also have pain-killing applications. Furthermore, in cases of chronic or extreme pain, it is not unusual for an individual to suffer some degree of depression; therefore, antidepressants may serve a dual role. Commonly prescribed anticonvulsants for pain include phenytoin, carbamazepine, and clonazepam. Tricyclic antidepressants include doxepin, amitriptyline, and imipramine.

Intractable (unrelenting) pain may be treated by injections directly into or near the main nerve supply that is transmitting the pain signal. One class of medications used in this way is corticosteroids. These are powerful anti-inflammatory agents. Pain decreases when the inflammation subsides. In other cases, local anesthetics, such as lidocaine, are used to create a neuromuscular blockade. However, these blockades are for short-term relief only, lasting a few hours, but the result is a break in the pain-response cycle that may have been self-perpetuating. These root blocks may also be useful in determining the site of pain generation. As the underlying mechanisms of pain transmission and perception are uncovered, other pain medications are being developed.

Drugs are not always effective in controlling pain. Surgical methods are used as a last resort if analgesics and local anesthetics fail. The least destructive surgical procedure involves implanting a device that emits low-level electrical signals. These signals disrupt the nerve and prevent it from transmitting the pain message. However, this method may not completely control pain and is not used frequently. Other surgical techniques involve destroying or severing the nerve (a procedure called a rhizotomy), but the use of this technique is limited by side effects, including residual numbness that may pose a risk for future injury.

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