***Pathophysiology - Chapter 4 - Pain

endorphins

"morphine within"--natural, opiatelike neurotransmitters linked to pain control and to pleasure. Endorphins include enkephalins, dynorphins, and beta-lipotropins.

The most common category encountered in cancer related pain is that which is caused by the advance of the disease.

As the tumors grow, they can cause infections and inflammation, which in turn cause increased pressure on nerve endings, stretching of tissues, or obstruction of vessels, ducts, or the intestines. This type of pain may be characterized as acute with sudden onset, intermittent, or chronic persisting over a long period of time.

Generalized pain

Fibromyalgia is a chronic myofascial (muscular) pain syndrome that typically causes generalized back and/or neck pain and muscle pain and causes specific areas of the body to become tender to the touch. Though it is similar to arthritis, it does not cause the same inflammation.

Chronic Pain

Long-term pain leads to different and often negative effects such as loss of employment or interference with personal relationships. • Chronic pain is usually more difficult to treat effectively than acute pain, and the prognosis may be less certain. • Chronic pain is often perceived by the patient as being more generalized, and it is difficult to discern an exact location. • Because a specific cause may be less apparent to the person experiencing the pain, the pain is more difficult to deal with and can be quite debilitating. • It is impossible to sustain a stress response over a long period of time, and the individual with chronic pain frequently is fatigued, irritable, and depressed. • Sleep disturbances are common, and appetite may be affected, leading to weight gain or loss. • Constant pain frequently affects daily activities and may become a primary focus in the life of the individual, thus complicating any measures to affect pain control by medication or other methods. Effective support from the health care team and a caring approach that does not minimize the person's pain may significantly reduce the client's focus on controlling pain. • Periods of acute pain may accompany exacerbations of chronic disease, making it more difficult for the patient to participate effectively in a pain management program. • Long-term pain usually reduces tolerance to any additional injury or illness. • Table 4-1 provides a brief comparison of acute and chronic pain.

Phantom Pain

Pain or another sensation such as itching or tingling occurs in some individuals, usually adults, after an amputation. Pain is perceived by the person as occurring in the lost limb and usually does not respond to usual pain therapies. The pain may resolve within weeks to months. Although the phenomenon is not fully understood, it appears that the brain "understands" the limb is still present when processing incoming stimuli. Research suggests that a history of prolonged or severe chronic pain before surgery increases the probability of phantom pain developing.

Atherosclerotic

The build-up of fats, cholesterol, and other substances in and on the artery walls. Pertaining to buildup of fatty substances within walls of arteries

neospinothalamic tract (two types of tracts in the spinothalamic bundle)

The fast impulses for acute sharp pain travel in the neospinothalamic tract.

Pain

a body defense mechanism and is a warning of a problem, particularly when it is acute. It is difficult to define because it can have many variable characteristics, and it is a subjective feeling, impossible to accurately measure.

neurotransmitter substance P

a compound thought to be involved in the synaptic transmission of pain and other nerve impulses. It is a polypeptide with eleven amino-acid residues.

Causalgia

a type of neuralgia that involves severe burning pain that can be triggered by normally "nontraumatic" stimuli such as a light touch, sound or cold. Like when your leg goes to sleep.

Headache

a very common type of pain. There are many categories of headache associated with different causes, and some have specific locations and characteristics.

Research has suggested that migraines may be caused by the following reactions:

a. Increased neural activity spreads over areas of the brain initiating pain stimuli in the trigeminal system, which are then conducted to the thalamus and pain centers in the sensory cortex. b. An accompanying reduction in serotonin is observed during migraine headaches and may cause the release of neuropeptides, which travel to the meninges covering the brain. c. These neuropeptides act on the smooth muscle of the blood vessels in the meninges, causing stretching and inflammation. The result is severe vascular pain.

Serotonin

another chemical released in the spinal cord that acts on other neurons in the spinal cord to increase the release of enkephalins. Clients with clinical depression often report chronic pain due to reduction in serotonin levels in the brain. In addition, natural opiate receptors are found in many areas of the brain, as are secretions of endorphins, which can block pain impulses at that level. The body has its own endogenous analgesic or pain control system that explains some of the variables in pain perception and can be used to assist in pain control.

Generalized and referred pains

are characteristic of visceral damage in the abdominal organs. In some conditions, such as acute appendicitis, the characteristics of the pain may change as pathologic changes occur.

Neuralgias

are examples of extremely painful conditions that are a result of damage to peripheral nerves caused by infection or disease.

Pain receptors or nociceptors

are free sensory nerve endings that are present in most tissues of the body (Fig. 4-1). These sensory nerves may be stimulated by thermal, chemical, or physical means. Thermal means refer to extremes of temperature, mechanical means could refer to pressure, and chemical sources could include acids or compounds produced in the body, such as bradykinin, histamine, or prostaglandin.

Headaches associated with congested sinuses, nasal congestion, and eyestrain

are located in the eye and forehead areas. Sinus headaches can be quite severe. These headaches are usually steady and relieved when the cause is removed.

Migraine headaches

are related to abnormal changes in blood flow and metabolism in the brain, but the exact mechanism is not yet fully understood. Characteristically, migraine headaches begin unilaterally in the temple area but often spread to involve the entire head. The pain is often accompanied or preceded by visual disturbances and dizziness, nausea and abdominal discomfort, and fatigue. These headaches may last up to 24 hours, and there is often a prolonged recovery period.

Neuropathic Pain

caused by trauma or disease involving the peripheral nerves. This type of pain can vary from a tingling to a burning or severe shooting pain. Movement can stimulate this pain as well as injured nerves that can become hyperexcitable and some neurons with low thresholds for thermal, mechanical or chemical stimuli may spontaneously fire.

opioids

chemicals that act on opiate receptors but are not derived from the opium poppy. Any drug or agent with actions similar to morphine.

tachycardia

fast heart rate

gate-control theory

has been modified as the complexity of pain is better realized, but the simple model serves as a useful tool and visual explanation of pain pathways that can be related to many concepts of pain and pain control. According to this theory, control systems, or "gates," are built into the normal pain pathways in the body that can modify the entry of pain stimuli into the spinal cord and brain. These gates at the nerve synapses in the spinal cord and brain can be open, thus permitting the pain impulses to pass from the peripheral nerves to the spinothalamic tract and ascend to the brain (Fig. 4-2). Or they may be closed, reducing or modifying the passage of pain impulses. Gate closure can occur in response to other sensory stimuli along competing nerve pathways that may diminish the pain sensations or by modulating or inhibitory impulses from higher centers in the brain. For example, application of ice to a painful site may reduce pain because one is more aware of the cold than the pain.

Treatment of severe migraine pain

is difficult, although ergotamine can be effective if it is administered immediately after the onset of the headache. Newer forms of ergotamine are available in a soluble tablet to be placed under the tongue, thus providing a more readily available and rapid-acting form of the drug and a combination of ergotamine and caffeine can also be used. The drugs of choice for severe migraine are the triptans that act on some 5-HT (5-hydroxytriptamine) receptors to block the vasodilation and release of vasoactive peptides in the brain. These drugs relieve the nausea and light sensitivity as well as pain and nausea.

ischemia

lack of blood supply. deficiency of blood in a particular area

Somatic pain

may arise from the skin (cutaneous) or from deeper structures such as bone or muscle, to be conducted by sensory nerves.

Mild migraine

may be treated with nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Advil, Motrin, and others) and acetaminophen (Tylenol and others).

Older children pain and responds to it physiologically

may flail their legs and arms and resist comfort measures, or they may become physically rigid. Children may find it difficult to describe their pain verbally. However, drawings of happy or sad faces, mechanical scales, or multicolored symbols can be used by children to better describe their feelings. Withdrawal and lack of communication are often the result of pain in older children and teens.

Referred pain

occurs when the sensations of pain are identified in an area some distance from the actual source (Fig. 4-3). Usually the pain originates in a deep organ or muscle and is perceived on the surface of the body in a different area. For example, pain in the left neck and arm is characteristic of a heart attack or ischemia in the heart. Pain in the shoulder may be due to stretching of the diaphragm. Multiple sensory fibers from different sources connecting at a single level of the spinal cord make it difficult for the brain to discern the actual origin of the pain.

Headache in the temporal area

often associated with temporomandibular joint (TMJ) syndrome, in which the underlying cause is a malocclusion involving the jaw or inflammation of the joint due to arthritis or poor body alignment which causes muscle tension in the neck that is transferred to the jaw.

Moderate migraine pain

often responds to a combination of acetaminophen, codeine, and caffeine, or acetaminophen, aspirin, and caffeine (Excedrin migraine).

Visceral pain

originates in the organs and travels by sympathetic fibers. Depending on the cause, pain may be sudden and short-term, marked primarily by a reflex withdrawal. For example, if one touches a hot object, the hand is involuntarily jerked away from the source of injury. Or pain may be relatively continuous, as when infection or swelling is present.

Central Pain

pain that is caused by dysfunction or damage to the brain or spinal cord. A lesion such as abscess, infarction, hemorrhage, tumor, or damage resulting from direct injury may cause central pain. This type of pain can be very localized or can involve a large area of the body. It is persistent, irritating, and can cause considerable suffered over an extended period of time.

analgesic

painkiller. medication that reduces or eliminates pain

pain threshold

refers to the level of stimulation required to activate the nerve ending sufficiently for the individual to perceive pain. The associated nerve fibers then transmit the pain signal to the spinal cord and brain. The pain threshold is relatively constant over time and between individuals. The ability to withstand pain or the perception of its intensity is referred to as pain tolerance; this varies considerably with past pain experience and overall state of health.

Headaches associated with muscle spasm and tension

result from emotional stress and cause the neck muscles to contract to a greater degree, pulling on the scalp. Sometimes when people work for long periods of time in one position, contraction and spasm of the neck muscles also result, causing a dull, constant ache usually in the occipital area. Tension headaches tend to persist for days or weeks.

Intracranial headaches

result from increased pressure inside the skull. Any space-occupying mass stretches the cerebral vascular walls or the meninges covering the brain. Causes of increased pressure include trauma with edema or hemorrhage, tumors, infections such as meningitis, or inflammation resulting from toxins such as alcohol. Headaches may be occipital or frontal in location depending on the site of the problem. Usually other indicators of increased intracranial pressure accompany the headache

Ischemic pain

results from a profound, sudden loss of blood flow to an organ or tissues in a specific area of the body. The decreased blood supply results in hypoxia, which leads to tissue damage and the release of inflammatory and pain-producing substances. The description of the pain may vary from aching, burning, or prickling to a strong shooting pain (particularly in an extremity). The exact symptoms depend on the location of the hypoxic tissue and can be characterized as either acute or chronic pain. Atherosclerotic disorders that cause blocking of arterial flow can cause ischemic pain, particularly in the lower extremities. Improving blood flow and preventing/reducing tissue hypoxia can do much to manage ischemic pain.

dermatome

spinal nerve conducts impulses from a specific area of the skin called a dermatome , and the somatosensory cortex is "mapped" to correspond to areas of the body so that the source of the pain can be interpreted in the brain . The dermatomes can be used to test for areas of sensory loss or pain sensation and thus determine the site of damage after spinal cord injuries.

Pain perception and response

subjective and depend on the conditioning of the individual. Factors such as age, culture, family traditions, and prior experience with pain shape one's perception and response to pain. For example, in certain groups it is customary to approach pain with stoic acceptance, whereas in other groups the proper response would include loud crying and wailing. Prior unpleasant experiences and anticipatory fear or anxiety can lower pain tolerance, magnifying the extent of the pain and the victim's response.

reflex response

sudden pain results in a motor, or efferent, impulse back to the muscles that initiates an involuntary muscle contraction to move the body away from the source of pain.

Transcutaneous electrical nerve stimulation (TENS)

ta therapeutic intervention that increases sensory stimulation at a site, thus blocking pain transmission. Alternatively, the brain can inhibit or modify incoming pain stimuli by producing efferent or outgoing transmissions through the reticular formation. Many factors can activate this built-in control system, including prior conditioning, the emotional state of the affected person, or distraction by other events. This last phenomenon has been observed in many individuals who feel no pain when injured suddenly but do experience delayed onset of pain once they are no longer distracted by the immediate emergency situation.

young infant pain and responds to it physiologically

tachycardia and increased blood pressure as well as characteristic facial expressions. Infants with their eyes tightly closed, their eyebrows low and drawn together, and their mouths open and square are probably in pain.

reticular formation

the brain stem, hypothalamus, thalamus, and other structures as they ascend to the somatic sensory area in the cerebral cortex of the parietal lobe of the brain.

Pain tolerance

the degree of pain, either its intensity or its duration, which is endured before an individual takes some action. Tolerance may be increased by endorphin release or reduced by other factors such as fatigue or stress. Tolerance does not necessarily depend on the severity of the pain. Rather, it varies among people and different situations.

reticular activating system (RAS)

the reticular formation in the pons and medulla influences the brain's awareness of the incoming pain stimuli. In clinical practice, many drugs depress the RAS, thereby decreasing the pain experienced. The hypothalamus plays a role in the response to pain through its connections with the pituitary gland and sympathetic nervous system. Response to pain usually involves a stress response (see Chapter 26) as well as an emotional response such as crying, moaning, or anger.

paleospinothalamic tract (two types of tracts in the spinothalamic bundle)

the slower impulses for chronic or dull pain use the paleospinothalamic tract.

unmyelinated C fibers (Two types of afferent fibers)

transmit impulses slowly. chronic pain— often experienced as a diffuse, dull, burning or aching sensation—is transmitted by C fibers. C fibers receive thermal, physical, and chemical stimuli from muscle, tendons, the myocardium, and the digestive tract as well as from the skin. The peripheral nerves transmit the afferent pain impulse to the dorsal root ganglia and then into the spinal cord through the dorsal horn or substantia gelatinosa

myelinated A delta fibers (Two types of afferent fibers)

transmit impulses very rapidly. Acute pain—the sudden, sharp, localized pain related to thermal and physical stimuli primarily from skin and mucous membranes—is transmitted by the A delta fibers

Cancer-Related Pain

very often associated with pain, usually chronic pain. This pain has been broken down into several categories: pain caused by the advance of the disease and resultant damage to the body, pain associated with the treatment of the disease, and pain that is the result of a coexisting disease unrelated to the cancer.

Acute Pain

• Acute pain is usually sudden and severe, but short term. • It indicates tissue damage and decreases once the cause has been treated. • It may be localized or generalized. • Acute pain usually initiates a physiologic stress response with increased blood pressure and heart rate; cool, pale, moist skin; increased respiratory rate; and increased skeletal muscle tension (see Chapter 26). • Vomiting may occur. • In addition, there may be a strong emotional response, as indicated by facial or verbal expression and a high anxiety level.