Pain (redirected from PAIN and Suffering)

Pain 

Definition

Pain is an unpleasant feeling that is conveyed to the brain by sensory neurons. The discomfort signals actual or potential injury to the body. However, pain is more than a sensation, or the physical awareness of pain; it also includes perception, the subjective interpretation of the discomfort. Perception gives information on the pain's location, intensity, and something about its nature. The various conscious and unconscious responses to both sensation and perception, including the emotional response, add further definition to the overall concept of pain.

Description

Pain arises from any number of situations. Injury is a major cause, but pain may also arise from an illness. It may accompany a psychological condition, such as depression, or may even occur in the absence of a recognizable trigger.

Acute pain

Acute pain often results from tissue damage, such as a skin burn or broken bone. Acute pain can also be associated with headaches or muscle cramps. This type of pain usually goes away as the injury heals or the cause of the pain (stimulus) is removed.

To understand acute pain, it is necessary to understand the nerves that support it. Nerve cells, or neurons, perform many functions in the body. Although their general purpose, providing an interface between the brain and the body, remains constant, their capabilities vary widely. Certain types of neurons are capable of transmitting a pain signal to the brain.

As a group, these pain-sensing neurons are called nociceptors, and virtually every surface and organ of the body is wired with them. The central part of these cells is located in the spine, and they send threadlike projections to every part of the body. Nociceptors are classified according to the stimulus that prompts them to transmit a pain signal. Thermoreceptive nociceptors are stimulated by temperatures that are potentially tissue damaging. Mechanoreceptive nociceptors respond to a pressure stimulus that may cause injury. Polymodal nociceptors are the most sensitive and can respond to temperature and pressure. Polymodal nociceptors also respond to chemicals released by the cells in the area from which the pain originates.

Nerve cell endings, or receptors, are at the front end of pain sensation. A stimulus at this part of the nociceptor unleashes a cascade of neurotransmitters (chemicals that transmit information within the nervous system) in the spine. Each neurotransmitter has a purpose. For example, substance P relays the pain message to nerves leading to the spinal cord and brain. These neurotransmitters may also stimulate nerves leading back to the site of the injury. This response prompts cells in the injured area to release chemicals that not only trigger an immune response, but also influence the intensity and duration of the pain.

Chronic and abnormal pain

Chronic pain refers to pain that persists after an injury heals, cancer pain, pain related to a persistent or degenerative disease, and long-term pain from an unidentifiable cause. It is estimated that one in three people in the United States will experience chronic pain at some point in their lives. Of these people, approximately 50 million are either partially or completely disabled.

Chronic pain may be caused by the body's response to acute pain. In the presence of continued stimulation of nociceptors, changes occur within the nervous system. Changes at the molecular level are dramatic and may include alterations in genetic transcription of neurotransmitters and receptors. These changes may also occur in the absence of an identifiable cause; one of the frustrating aspects of chronic pain is that the stimulus may be unknown. For example, the stimulus cannot be identified in as many as 85% of individuals suffering lower back pain.

Scientists have long recognized a relationship between depression and chronic pain. In 2004, a survey of California adults diagnosed with major depressive disorder revealed that more than one-half of them also suffered from chronic pain.

Other types of abnormal pain include allodynia, hyperalgesia, and phantom limb pain. These types of pain often arise from some damage to the nervous system (neuropathic). Allodynia refers to a feeling of pain in response to a normally harmless stimulus. For example, some individuals who have suffered nerve damage as a result of viral infection experience unbearable pain from just the light weight of their clothing. Hyperalgesia is somewhat related to allodynia in that the response to a painful stimulus is extreme. In this case, a mild pain stimulus, such as a pin prick, causes a maximum pain response. Phantom limb pain occurs after a limb is amputated; although an individual may be missing the limb, the nervous system continues to perceive pain originating from the area.

Causes and symptoms

Pain is the most common symptom of injury and disease, and descriptions can range in intensity from a mere ache to unbearable agony. 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.

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, and freezing. These same stimuli would not generate much of a response in the intestine. Intestinal pain arises from stimuli such as swelling, inflammation, and distension.

Diagnosis

Pain is considered in view of other symptoms and individual experiences. 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 narrow down the possibilities. In some cases, such as lower back pain, a specific cause may not be identifiable. Diagnosis of the disease causing a specific pain is further complicated by the fact that pain can be referred to (felt at) a skin site that does not seem to be connected to the site of the pain's origin. For example, pain arising from fluid accumulating at the base of the lung may be referred to the shoulder.

Since pain is a subjective experience, it may be very difficult to communicate its exact quality and intensity to other people. There are no diagnostic tests that can determine the quality or intensity of an individual's pain. Therefore, a medical examination will include a lot of questions about where the pain is located, its intensity, and its nature. Questions are also directed at what kinds of things increase or relieve the pain, how long it 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 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 neurotransmitters. Drugs from different classes may be combined to handle certain types of pain.

Nonopioid analgesics include common over-the-counter 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 class.

Narcotic analgesics are only available with a doctor's prescription and are used for more severe pain, such as cancer pain. These drugs include codeine, morphine, and methadone. Addiction to these painkillers is not as common as once thought. Many people who genuinely need these drugs for pain control typically do not become addicted. However, narcotic use should be limited to patients thought to have a short life span (such as people with terminal cancer) or patients whose pain is only expected to last for a short time (such as people recovering from surgery). In August 2004, the Drug Enforcement Administration (DEA) issued new guidelines to help physicians prescribe narcotics appropriately without fear of being arrested for prescribing the drugs beyond the scope of their medical practice. DEA is trying to work with physicians to ensure that those who need to drugs receive them but to ensure opioids are not abused.

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, since in cases of chronic or extreme pain, it is not unusual for an individual to suffer some degree of depression; 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 nerve that is transmitting the pain signal. These root blocks may also be useful in determining the site of pain generation. As the underlying mechanisms of abnormal pain 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 drugs and local anesthetics fail. The least destructive surgical procedure involves implanting a device that emits 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, but the use of this technique is limited by side effects, including unpleasant numbness.

Alternative treatment

Both physical and psychological aspects of pain can be dealt with through alternative treatment. Some of the most popular treatment options include acupressure and acupuncture, massage, chiropractic, and relaxation techniques such as yoga, hypnosis, and meditation. Herbal therapies are gaining increased recognition as viable options; for example, capsaicin, the component that makes cayenne peppers spicy, is used in ointments to relieve the joint pain associated with arthritis. Contrast hydrotherapy can also be very beneficial for pain relief.

Lifestyles can be changed to incorporate a healthier diet and regular exercise. Regular exercise, aside from relieving stress, has been shown to increase endorphins, painkillers naturally produced in the body.

Prognosis

Successful pain treatment is highly dependent on successful resolution of the pain's cause. Acute pain will stop when an injury heals or when an underlying problem is treated successfully. Chronic pain and abnormal pain are more difficult to treat, and it may take longer to find a successful resolution. Some pain is intractable and will require extreme measures for relief.

Prevention

Pain is generally preventable only to the degree that the cause of the pain is preventable. For example, improved surgical procedures, such as those done through a thin tube called a laparascope, minimize post-operative pain. Anesthesia techniques for surgeries also continuously improve. Some disease and injuries are often unavoidable. However, pain from some surgeries and other medical procedures and continuing pain are preventable through drug treatments and alternative therapies.

Resources

Periodicals

"Advances in Pain Management, New Focus Greatly Easing Postoperative Care." Medical Devices & Surgical Technology Week September 26, 2004: 260.

Finn, Robert. "More than Half of Patients With Major Depression Have Chronic Pain." Family Practice News October 15, 2004: 38.

"New Guidelines Set for Better Pain Treatment." Medical Letter on the CDC & FDA September 5, 2004: 95.

Organizations

American Chronic Pain Association. P.O. Box 850, Rocklin, CA 95677-0850. (916) 632-0922. 〈http://members.tripod.com/∼widdy/ACPA.html〉.

American Pain Society. 4700 W. Lake Ave., Glenview, IL 60025. (847) 375-4715. http://www.ampainsoc.org.

Key terms

Acute pain — Pain in response to injury or another stimulus that resolves when the injury heals or the stimulus is removed.

Chronic pain — Pain that lasts beyond the term of an injury or painful stimulus. Can also refer to cancer pain, pain from a chronic or degenerative disease, and pain from an unidentified cause.

Neuron — A nerve cell.

Neurotransmitters — Chemicals within the nervous system that transmit information from or between nerve cells.

Nociceptor — A neuron that is capable of sensing pain.

Referred pain — Pain felt at a site different from the location of the injured or diseased part of the body. Referred pain is due to the fact that nerve signals from several areas of the body may "feed" the same nerve pathway leading to the spinal cord and brain.

Stimulus — A factor capable of eliciting a response in a nerve.

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pain (pan) a feeling of distress, suffering, or agony, caused by stimulation of specialized nerve endings.

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bearing-down pain  pain accompanying uterine contractions during the second stage of labor.

false pains  ineffective pains resembling labor pains, not accompanied by cervical dilatation.

growing pains  recurrent quasirheumatic limb pains peculiar to early youth.

hunger pain  pain coming on at the time for feeling hunger for a meal; a symptom of gastric disorder.

intermenstrual pain  pain accompanying ovulation, occurring during the period between the menses, usually about midway.

labor pains  the rhythmic pains of increasing severity and frequency due to contraction of the uterus at childbirth.

phantom limb pain  pain felt as though arising in an absent (amputated) limb.

psychogenic pain  symptoms of physical pain having psychological origin.

referred pain  pain felt in a part other than that in which the cause that produced it is situated.

rest pain  a continuous burning pain due to ischemia of the lower leg, which begins or is aggravated after reclining and is relieved by sitting or standing.

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pain (pn)

n.

1. An unpleasant sensation occurring in varying degrees of severity as a consequence of injury, disease, or emotional disorder.

2. One of the uterine contractions occurring in childbirth.

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pain,

n unpleasant emotional or physical sensation, often associated with potential or actual tissue damage and classified as acute, chronic, or cancer-related. See also cancer-related pain.

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pain,

n an unpleasant sensation created by a noxious stimulus mediated along specific nerve pathways to the central nervous system, where it is interpreted. The sensation of pain is a protective mechanism that warns of danger without giving too much information about the specific nature of the danger. It initiates nociceptive reflexes.

pain and suffering,

n an element in a claim for damages in a liability lawsuit. It requests compensation to an individual for mental and physical pain and discomfort as a result of an injury.

pain, assessment,

n an evaluation of the reported pain and the factors that alleviate or exacerbate a patient's pain; used as an aid in the diagnosis and the treatment of disease and trauma.

pain, chest,

n pain that occurs in the chest region because of disorders of the heart (e.g., angina pectoris, myocardial infarction, or pericarditis), pulmonary artery (pulmonary embolism or hypertension), lungs (pleuritis), esophagus (“heartburn”), abdominal organs (aerophagia, biliary tract disease, splenic infarction, or gaseous distention in the splenic flexure), or the chest wall (neoplasia, costochondral strains, trauma, hyperventilation, or muscular tension).

pain clinic,

n a multidisciplinary association of health care professionals devoted to the diagnosis and treatment of patients with acute and chronic pain.

pain, deep,

n dull, aching, or boring pain originating in muscles, tendons, and joints. It is poorly localized and tends to radiate.

pain dysfunction syndrome,

n in dentistry, a phrase used to describe a condition in patients who appear to have a psychophysiologic basis for stress overload on the temporomandibular joint. The preferred term is
mandibular stress syndrome.

pain, ghost,

n See odontalgia, phantom.

pain mechanism,

n the network that communicates unpleasant sensations and the perceptions of noxious stimuli throughout the body in association with both physical disease and trauma involving tissue damage.

pain, nerve ending,

n a receptor nerve ending that is relatively primitive and ends in an undifferentiated arborization. The nerve ending for the sensation of pain is a protective mechanism that warns of danger without giving too much information about the specific nature of the danger. The danger stimuli give rise to nociceptive reflexes, or defensive, protective, or withdrawal movements. The nociceptive reflexes supersede other, less urgent, reflexes that are thus inhibited.

pain, projected pathologic,

n pain erroneously perceived to arise in a peripheral region because of a stimulus from end-organs supplying the region (e.g., sciatic pain). Actually the stimulus occurred somewhere along the pain pathway from the nerve to the cortex.

pain, reaction,

n the individual's manifestation of the unpleasant sensation.

pain, referred,

n pain caused by an agent in one area but manifested in another (e.g., pain caused by caries in the maxillary third molar may be referred to the mandible, so the source of pain appears to be in the mandible).

pain stimulus,

n an agent that has the potential to induce pain, whether through chemical, mechanical, or thermal means.

pain, tactile stimuli,

n any of a number of physical sources that may aggravate dentin hypersensitivity, such as dental instruments, toothbrush bristles, ill-fitting oral prostheses, and various personal oral habits a patient may have.

pain, thermal stimuli,

n dentin hypersensitivity related to abrupt changes in temperature of teeth as a result of contact with very cold or very hot foods and liquids, rapid intake of air through the oral cavity, and during professional oral hygiene procedures requiring rapid drying of teeth.

pain threshold,

n the point at which a stimulus causes pain. It varies widely among individuals.

pain, tolerance,

n the maximum pain level an individual is able to withstand.

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pain

a feeling of distress, suffering or agony, caused by stimulation of specialized nerve endings. Its purpose is chiefly protective; it acts as a warning that tissues are being damaged and induces the sufferer to remove or withdraw from the source.

All receptors for pain stimuli are free nerve endings of groups of myelinated or unmyelinated neural fibers abundantly distributed in the superficial layers of the skin and in certain deeper tissues such as the periosteum, surfaces of the joints, arterial walls, and the falx and tentorium of the cranial cavity. The distribution of pain receptors in the gastrointestinal mucosa apparently is similar to that in the skin; thus, the mucosa is quite sensitive to irritation and other painful stimuli. Although the parenchyma of the liver and the alveoli of the lungs are almost entirely insensitive to pain, the liver as an organ and the bile ducts are extremely sensitive, as are the bronchi, ureters, parietal pleura and peritoneum.

Some pain receptors are selective in their response to stimuli, but most are sensitive to more than one of the following types of excitation: (1) mechanical stress of trauma; (2) extremes of heat and cold; and (3) chemical substances, such as histamine, potassium ions, acids, prostaglandins, bradykinin and acetylcholine.

The conscious perception of pain probably takes place in the thalamus and lower centers; interpretation of the quality of pain is probably the role of the cerebral cortex.

There are some naturally occurring internal systems in the body that are known to control pain but none of them has been completely verified. One of the best known is the gate control system in which it is thought that pain impulses are mediated in the substantia gelatinosa of the spinal cord.

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abdominal pain

pain occurring in the area between the thorax and pelvis. Manifestations vary between species. Identifiable syndromes include: (1) horse—pawing, flank watching, rolling, straddling as though to urinate, lying on the back; (2) cattle—may depress back and paddle with hindfeet but mostly arched back, grunting, immobility; (3) dogs and cats—arched back, grunting, depression, reluctance to move. Sometimes there is elevation of the hindquarters, with the chest and forelegs on the ground (the so-called 'praying dog' attitude).

Beagle pain syndrome

see beagle pain syndrome.

projected pain

pathology in one area can affect the nerve supply to a distant area in which pain is experienced.

pain receptors

free nerve endings of tufts of fine points or buttons.

referred pain

pain felt in an area distant from the site of pathology but not mediated through a common innervation. There is no evidence that referred pain occurs in animals but it seems likely on anatomical grounds.

pain threshold

the lowest level at which a stimulus can be applied and cause perceptible pain.

pain tolerance

the level of stimulation at which pain becomes intolerable.