Pain
Definition
Pain, medically termed "nociception," is a response to noxious stimuli that is conveyed to the brain by sensory neurons. The discomfort signals actual or impending 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, but it may also be a warning of impending damage, such as angina or the pain associated with appendicitis or the body's attempt to pass a kidney stone. Acute pain is also associated with severe headaches (such as migraines) or muscle cramps. This latter 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—to provide 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 other types of pain
Chronic pain refers to pain that persists after an injury is apparently healed, 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 by the pain and its cause.
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 molecular or cellular 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.
Other types of pain include allodynia, hyperalgesia, and phantom-limb pain. These pain categories are neuropathic, indicating damage to the nervous system. Allodynia is 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 (like herpes zoster) 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 has been amputated; although an individual is missing the limb, the nerve pathways may still perceive pain as originating from the absent extremity, on an intermittent basis.
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.
Alternative treatment
Both physical and psychological aspects of pain can be dealt with through alternative treatment. Some of the most popular treatment options are acupressure and acupuncture, massage, chiropractic adjustments, 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 associated with arthritis; it serves as a counteractive or contradictory pain site—the mind focuses on it, rather than on the joint pain. Contrast hydrotherapy can also be very beneficial for pain relief.
Behavioral modification to incorporate a healthier diet and regular exercise may be of help. Aside from relieving stress, regular exercise has been shown to increase endorphins, pain alleviators that are naturally produced in the body.
Health care team roles
As members of the health care team, advanced practice nurses (A.P.N.s), registered nurses (R.N.s), and licensed practical nurses (L.P.N.s) are responsible for assessing the pain response that paints demonstrate, implementing proper pain-medication therapy, assessing the outcomes of pain therapy, documenting the patient's perception of pain severity using a pain scale, as well as describing other pain characteristics and teaching patients painmanagement techniques.
Joint Commission on Accreditation of Healthcare Organizations standards
The Joint Commission on Accreditation of Healthcare Organizations (JCAHO), which is the accreditating body for all health care facilities, is focusing on auditing health care organizations on their appropriate pain-assessment and pain-management techniques by way of newly published pain standards. Health care institutions are being held accountable for outcomes of pain management according to the standards, and A.P.N.s, R.N.s, and L.P.N.s must be aware of these standards in order to modify practices to meet the new regulations. The 2001 JCAHO standards are:
- to acknowledge that every patient has a right to pain evaluation and pain management
- to evaluate pain in every patient
- to do a thorough examination when the presence of pain has been identified
- to document the examination in a specific format that supports standard reexamination and review
- to establish a customary protocol for observation and management of pain
- to teach practitioners and guarantee health care team proficiency on pain-management standards
- to create guidelines that incorporate adequate dispensing of appropriate medication for pain control
- to create and implement educational materials for pain control to give to patients and families
- to address pain-control measures upon the patient's release from the facility
- to establish tools to evaluate the success of pain management
Assessing characteristics of pain
The health care team must be able to describe the characteristics of pain when identified by the patient. Subjective data should be collected. Information on the following eight variables is essential to get a clear picture of the patient's experience of pain:
- Describe the pain (sharp, dull, aching, stabbing).
- How often (constant or transient—comes and goes).
- Where (point to the exact location, does the pain radiate, or spread)?
- Intensity: Assign a number from 0 (no pain) to 10 (the worst pain you have ever had).
- How long: all the time, or episodes of seconds, minutes, hours?
- Does anything help to relieve the pain (a certain position, medication, ice, or warm compresses)?
- Does anything make it worse (a certain position, exercise)?
- Have you ever experienced this type of pain before?
Importance of pain reassessment
As the R.N. or L.P.N., assessing the outcomes of pain-management therapies is an important part of the health care role. Intravenous medications should provide relief within 10 minutes, intramuscular medications are active within 30 to 40 minutes, and oral medication takes effect within one hour or less. Pain reassessment takes these times into consideration. Reassessment in these time frames allows accurate outcomes evaluation for pain management.
Patient education
Teaching appropriate pain-medication administration as well as informing the patient of ancillary pain-management techniques are important in patient education. A person in pain should understand that various medications take time to be absorbed and start working. Also, teaching relaxation techniques, such as meditation, imagery, and aromatherapy, offers measures that complement pain-medication effectiveness and may even reduce the need for medication. Many patients are afraid to take some pain medications, for fear of becoming addicted. Explaining that the appropriate use of the medication, in the dose prescribed and in direct proportion to the level of pain, will avoid the potential for addiction. Health care team members are patient advocates, and they should not allow their patient to suffer.
Prognosis
Successful pain management is dependent on successful identification of the pain's cause. Acute pain will stop when an injury heals or when an underlying condition is treated successfully. Chronic pain is more difficult to treat, and it may take longer to achieve a successful outcome. 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; diseases and injuries may be unavoidable. Some injuries, or reinjury, can be avoided. For example, proper muscle use and positioning when lifting heavy objects will prevent back injury. Increased pain, pain from surgery and other medical procedures, and continuing pain may be preventable through appropriate treatments and therapies.
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. The term may 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.
Transient—Staying in one place only for a brief amount of time.
