Attorneys' Textbook of Medicine (Third Edition) © Copyright 2008, Matthew Bender & Company, Inc., a member of the LexisNexis Group. All rights reserved.
CHAPTER 177 TREATMENT OF PAIN excerpt AUTHOR: David Cramer, MD P 177.00 INTRODUCTION More than any other reason, people consult their physicians seeking relief of pain. Ideally the underlying cause of pain, whether disease or injury, will be identified and corrected, thereby relieving the pain. When, however, the cause of pain remains obscure or is not treatable, some means of alleviating the pain itself must be sought. Despite major advances in understanding how and why pain can develop and persist, and the advent of many sophisticated medical and surgical treatments, physicians are by no means always able to substantially relieve their patients' pain. [177.01] Complex Nature of Pain Pain is far from the simple matter it may sometimes seem to be. The same injury or disease may produce trivial distress in one individual and intolerable pain in another. Furthermore, seemingly severe pain may continue for years after an injury has healed or disease is cured. The damage sustained by a body part or organ is only one determinant of the severity and quality of pain. Past episodes of pain, cultural influences, and whether a patient understands the origin of the pain and feels in some degree of control, all contribute to the pain experience. Prophetically, Plato asserted that pain arises not only from peripheral stimulation, but also from an emotional experience in what he called the soul (Caillet, 1993). It is becoming increasingly clear that the ''subjective'' aspects of pain may actually influence the nerve signals that convey painful feelings from the affected part of the body to the brain.
Successful pain management requires an appreciation of how physical, psychological and sociocultural factors interact to produce pain. The complex nature of pain, particularly when chronic, often dictates a multidisciplinary approach to its treatment. Flexibility is the key: management must be continually modified according to the severity and extent of whatever is causing the pain, previous treatment and the response to it and the patient's personal preferences (NCI, 1996).
[177.02] Definition of Pain Pain is commonly thought of as a warning signal that something is wrong. As such, it may be viewed as adaptive if it leads to the discovery of what is causing pain and to its abolition. An operational definition of pain (Feuerstein, 1994) takes into account: the patient's actual experience as described; ''pain behavior''-- observable expressions and actions that suggest a patient is suffering; how pain affects the patient's functioning at home and at work; how emotional factors alter the perception and expression of pain; and a cognitive component involving how sensitive the patient is to pain, and how much attention is paid to bodily discomfort. P 177.10 TYPES OF PAIN Pain may be classified, first, by its time course: whether it is acute, subacute or chronic. A second way of classifying pain is to specify the particular sensory mechanism involved. In addition, there are a number of clinical pain syndromes associated with particular injuries or diseases. [177.11] Acute Pain Acute pain develops instantly (as after an injury such as a laceration), or over a period of hours to a few days. Migraine headache, appendicitis and dental abscess are examples. It is this type of pain which typically serves as a warning that something has gone wrong in the body. Subacute pain is similar but develops over a few weeks, rather than hours or days. [177.12] Chronic Pain Pain that continues longer than three months generally is termed chronic, though it need not be constantly present. Typically this type of pain is less well localized than acute pain. It also differs in quality, tending to be described as ''nagging,'' ''deep,'' or ''boring,'' rather than ''sharp'' or ''cutting'' - terms often used to describe acute pain. Chronic pain often goes on well past the point where it is a useful warning sign. It may even continue after a lesion has healed or a disease is seemingly cured. When this is the case, chronic pain is liable to affect the patient's psychological and social status, and compromise his or her ability to function.
[177.13] Physiological Distinctions Pain often is classified according to how it is produced (its mechanism). There may be overlap between different physiological (functional) categories of pain. And a patient may have more than one type of pain at the same time. The skin and other tissues and organs of the body have free nerve endings called nociceptors, which are sensitive to mechanical, thermal or chemical stimuli. When exposed to such stimuli, the nociceptors activate their nerves and send pain signals to the brain. Nociceptive pain may feel sharp and intense (touching a hot object), aching (low back pain) or deep and severe (invasion by cancer). This type of pain very often can be relieved by narcotic or other analgesics, alternative medical measures or surgery. Neuropathic pain occurs when nerves are damaged mechanically, by a virus (herpes zoster), by a toxic substance such as mercury, or by any number of other causes. A localized growth of a nerve (neuroma) may cause this type of pain. When nerves in the brain and spinal cord or ''outside'' (peripheral) nerves are damaged to the point where nerve signals are actually interrupted, the result is deafferentation pain. The term refers to dysfunction of afferent nerves, those bringing information (such as pain) from the outside world to the brain. This type of pain (also called causalgia) may be very severe. It often has a burning quality. Or, it may be described not as pain itself but as an unpleasant sensation in part of the body that otherwise has lost feeling (anesthesia). Some patients report being exquisitely sensitive to painful stimuli (hyperalgesia), or as having an exaggerated reaction to what should be a minor stimulus (hyperpathia). This form of pain tends not to respond to drugs or surgery (although antidepressant drugs hold some promise). So-called psychogenic pain is seen in patients with psychological or psychiatric disorders. It is diagnosed only after all bodily (somatic) causes of pain have been ruled out. (Nashold, Jr. et al., 1994; Wilson and Lamer, 1992). [177.14] Clinical Pain Syndromes Pain syndromes may be defined by the part of the body they affect. Examples are the combination of headache with facial pain, pain in the face and mouth (orofacial pain), low back pain and pain affecting the neck and upper extremity. Other syndromes are associated with particular disease states or conditions. They include obstetrical pain, postoperative pain, pain resulting from sports injuries, and pain caused by cancer or AIDS.1 Certain types of nerve damage or disease also may produce recognizable clinical syndromes. Neuralgia is a form of pain caused by infection or disease that injures peripheral nerves. A special case is postherpetic neuralgia complicating infection by herpes virus. Patients requiring amputation of a limb may experience severe and persistent pain (phantom pain) as if the extremity were still present (Raj, 1992).2 FOOTNOTES: Footnote 1. See also ch. 176. Footnote 2. See also ch. 2A.
177.20 PHYSIOLOGY OF PAIN An understanding of what actually happens in the body to produce the experience of pain will help explain how various treatments work, and why all attempts at treating pain sometimes fail. Most often pain occurs when signals are sent along certain neural pathways. In other instances, mechanisms that ordinarily inhibit pain are suppressed, permitting feelings of pain to emerge. Mechanisms of pain production are discussed briefly in this section.176. for a more detailed discussion of the mechanisms of pain. [177.21] Peripheral Nervous System Stimuli cause pain by activating receptors, the end-branches of sensory nerves lying just below the surface of the skin. The nociceptors are those receptors that are especially sensitive to pain-causing stimuli. The nerve ending converts the stimulus into a train of electrical impulses, the nerve signal, that passes along the peripheral nerve to the spinal cord. The strength of a stimulus may determine whether or not it will be painful. Light pressure, for instance, is not felt as painful, but increased pressure eventually will cause pain (Hall, 1994). [177.22] Spinal Cord In cross-section the spinal cord is seen to have a central butterfly-shaped area of gray matter, consisting of the bodies of nerve cells. The long extensions of these nerve cell bodies form the axons that transmit nerve signals to and from the brain. Each axon is protected by a covering sheath of a substance called myelin. The afferent peripheral nerves, which bring messages from the body surface to the brain, enter the posterior (dorsal) part of the spinal cord through nerve roots. Their cell bodies lie together in small masses called ganglia which are just outside the spinal cord itself. Each of their axons has two branches, one passing from the outside of the body to the ganglion, and the other from the ganglion along the dorsal root into the spinal cord. Nerve cells are connected to one another by tiny spaces called synapses, which serve as relay points. At the many points where nerve cells meet, pain signals may be either strengthened or weakened (inhibited). Pain signals pass from the dorsal part of the spinal cord to the brain in nerve bundles called tracts. A very important one is the spinothalamic tract, which sends nerve fibers to the thalamus, a central brain structure. From this point signals proceed to the outer layer of the brain, the cortex. Many other tracts send nerve signals to the reticular system in the lower part of the brain. Messages also go to the limbic system, a part of the cortex that controls behavior and emotion, as well as directly to the cortex itself. The fact that nerves carrying pain signals run together in tracts makes it possible to relieve pain by surgically cutting the right tract (Melzack and Wall, 1988). [177.23] Brain In contrast to what was formerly thought, there is no single ''pain center'' in the cerebral cortex. All sensory signals including pain messages are received in the cortex and relayed to other parts of the brain. In effect, the entire brain contributes
to the pain experience. At the same time, the brain is able to suppress pain through descending (efferent) nerve tracts that inhibit sensory nerve signals. Exactly how nerve signals produce pain remains uncertain, but a number of chemicals may play a role. ''Substance P'' is a brain protein that apparently transmits incoming pain impulses. Other chemical mediators of pain may include prostaglandin E, inflammatory substances called leukotrienes and histamine. All these chemicals act at the site where pain is felt. They may directly activate pain receptors, or cause changes such as tissue swelling and inflammation which have the same effect (Cailliet, 1993). [177.24] Inhibition of Pain The existence of neural mechanisms that can inhibit nerve signals both peripherally and in the brain can help explain many observations: that injury and pain are not always related in a consistent manner, that non-painful stimuli may produce pain and that pain often continues after an injury has healed. Inhibitory nerve cells in the spinal cord help determine which incoming signals will reach the brain. At the same time, inhibitory nerve fibers from the brain connect with nerve cells in the spinal cord and suppress them.  Gate-Control Theory An ingenious theory was proposed by Melzack and Wall in 1965 that helps explain some of these puzzling observations. They proposed that special cells in the reticular formation of the brain and an area called the substantia gelatinosa can control the flow of pain signals and determine which, if any, will reach the brain. Pain is felt when this ''gate'' is open, but is diminished or absent when it is closed. It now is recognized that, while the gate-control theory may be right, it is not the whole story. At least three other neural systems exist which can influence the transmission of pain signals (Hoffert, 1992).  Enkephalins An important element in pain relief is the enkephalins, a type of built-in (endogenous) narcotic produced by cells in the dorsal horn of the spinal cord. The enkephalins act at synapses between nerve cells to suppress incoming nerve signals (Wilson and Lamer, 1992). When released by nerve cells, enkephalins inhibit the release of substance P. In this way they are able to stop incoming pain signals from reaching the brain. It is as if the body produced its own pain-killer, which in structure closely resembles the opiates so often used to treat pain. [177.25] Mechanism of Pain Following Nerve Injury When a peripheral nerve is injured, the normal input from outside stimuli is cut off. Instead, signals that normally would be suppressed by inhibitory mechanisms pour in. Nerve injury also keeps the usual chemicals vital for normal nerve cell function from passing along the nerves. The net result is that nerve cells in the brain and spinal cord become highly excitable. They start responding to stimuli from parts of the body with which they have no direct connection. This condition is called denervation hypersensitivity. It may well explain the pain that often continues long after a nerve injury has healed. It also can explain the ''phantom limb'' phenomenon. Cells, for instance, that used to serve an amputated foot now respond to stimulation of the knee, making the patient feel as if the foot was still there (Melzack and Wall, 1988).
P 177.30 EVALUATION AND DIAGNOSIS Pain is a symptom, and as such is a private experience that is not objectively measurable. Although the physician can find clues in how the patient looks and behaves, the patient's own description of pain is of paramount importance. There are, however, ways of codifying what the patient has to say, and thereby gaining some idea of how intense the pain is and how much it changes over time. In certain cases, imaging the site of pain can be helpful. [177.31] History How the patient describes pain will sometimes suggest a specific condition. Back pain that is made worse when the patient sits or walks, for instance, is good evidence of degenerative disease of a spinal disc. When back pain gets worse in bed, however, a spinal tumor may be responsible. The exact words the patient uses when describing the pain are often quite helpful in distinguishing between various pain syndromes. What makes the pain worse, and what tends to ease it? The patient should be asked about past instances of pain and whether any particular methods have proved helpful in controlling pain. How the patient feels about using opioids and other types of medication should be established; have substances been abused? Whether the patient also has suffered anxiety or depression may be a key factor. Of importance as well is what the patient knows about pain treatment, what is expected, and any preferences the patient may have for (or against) a given type of treatment (PHS, 1992). The physician should know how the patient's pain has altered sleep or eating habits, and how much it has interfered with activities at work, home or play. The McGill Pain Questionnaire was developed by Melzack to help the patient describe the pain experience in detail. The most commonly used psychological measure used in patients with chronic pain is the Minnesota Multiphasic Personality Inventory. Older patients may have to be prompted frequently when asked about symptoms. Observing how an elderly person responds to pain medication may be revealing. When evaluating children, repeated assessments and careful observation will help clarify the picture (Hinnant, 1994). [177.32] Physical Examination The part of the body where the patient feels pain is carefully examined. Redness and swelling may suggest inflammation. The examiner should probe for tender points, and monitor pain as nearby joints are moved through their full range. Stretching an arm or leg may worsen pain if a major nerve or group of nerves (plexus) is inflamed or compressed by some other structure. A neurological examination may reveal signs that nerves are not functioning properly, marked by muscle weakness, loss of sensation or abnormal reflexes. The physician should know that pain sometimes is referred to a site other than where it arises. Disease of an internal organ may make a particular area of skin hypersensitive to painful stimuli. [177.33] Laboratory and Radiographic Studies The electromyogram (EMG), by recording electrical activity from muscles, can show
that a nerve which controls a particular muscle or group of muscles is not working. Nerve conduction studies determine how well nerves transmit their signals. Together these studies may show whether the cause of pain resides in the spinal cord, nerve root, or the nerve itself. Another way of assessing nerve function is through evoked potentials, whereby electrical nerve responses to applied stimuli are recorded (Waldman, 1996). Pain in a bone or joint may be pinpointed by plain x-rays, computed tomographic (CT) scanning, or magnetic resonance imaging (MRI).3 Bone scans made with a radionuclide contrast medium are often very helpful in locating the source of pain, and sometimes its cause as well. These scans can disclose a hidden or tiny fracture, demonstrate the spread of cancer and diagnose joint disease. Ultrasound is a safe and often revealing study. In special cases it may help to inject a contrast material into a joint, the spinal column (myelography), or a major blood vessel (Abrams, et al., 1996). FOOTNOTES: Footnote 3. See also ch. 70. P 177.40 GENERAL PRINCIPLES OF TREATMENT As for centuries past, there remain three fundamental ways of relieving pain. Analgesic drugs (pain-killers) are a mainstay of treatment. The choices available and the means of delivering them are both widening. Furthermore, drugs are being increasingly used in combination with what are called sensory-modulation techniques. These range from anesthetic methods (nerve blocks) and sophisticated surgical procedures to a broad range of physical methods. Finally, recognizing the importance of the psychological aspect of pain have prompted attempts to allow patients to use their own resources to cope with chronic pain (Wurm, 1992). Relaxation techniques, biofeedback, hypnosis, behavioral methods, and cognitive approaches all fall into this category.4 [177.41] Therapeutic Approach Whenever possible the specific condition producing pain will be the object of treatment. But this often is not possible in patients with chronic pain, and for some types of pain there may be no specific treatment. In these cases the goal must be to help patients carry on with their lives and their work as well as possible while controlling pain to some degree, hopefully without long- term narcotics (Wurm, 1992). An accepted guideline is to first try a relatively noninvasive procedure such as a local nerve block with anesthetic or electrical nerve stimulation before resorting to a more drastic approach, such as destroying a nerve. Increasingly today, multiple measures are given concurrently rather than sequentially in the hope that they will augment one another. For instance, a narcotic and a nonnarcotic drug will control pain better when used together than when each is used separately. A patient with chronic pain may benefit when, in addition to analgesics, a relaxation technique is taught and appropriate physical therapy is carried out. Prevention always is better than treatment. Caregivers should encourage their patients to ask for relief before pain becomes severe (when it will be more difficult to control). Relaxation exercises can help control postoperative pain (PHS, 1992).
Chronic pain is best managed using a team approach: the patient, the family, and all health care providers involved. The patient should be an active, not a passive member of the team. Patients and their relatives should know that numerous effective and safe ways of relieving pain are available, and they need not be reluctant to ask for relief (NCI, 1996). [177.42] Use of Drugs The issue of whether, and when people suffering chronic pain should receive narcotic drugs remains as controversial as ever. Most experts agree that fear of addiction (psychological dependence) should not cause these effective analgesics to be withheld from a patient with end- stage cancer who is not expected to live much longer. On the other hand, caution is appropriate for those with a longer life expectancy or patients with benign disease that is causing severe pain. They may require ever larger doses to keep the pain under control (tolerance), or they may become physically dependent and develop withdrawal symptoms if the dose is lowered or the drug dropped altogether (Freidberg, 1992). Patients with cancer should not, however, be confused with street addicts. They seek pain relief, not euphoria. When patients using narcotics gain relief from a neurosurgical procedure, the drugs often can be rapidly withdrawn with no signs of dependency (Melzack and Wall, 1988). Furthermore, many patients who are allowed to give themselves narcotics actually use less than if placed on a conventional dose schedule. Their dosage tends to stabilize (assuming disease does not progress), and they do not become addicted. [177.43] Placebo Effect A placebo is a substance that does not have any effect on the body, but nevertheless relieves pain. The so-called placebo effect is an element of pain control that must not be ignored. In some respects a placebo does act like a ''real'' drug. In headache patients, a larger amount of placebo will be more effective. The physician must take care not to lose the patient's trust when trying a placebo. When a placebo does relieve pain, it does not mean that there really was no pain. In general, placebos are about half as effective as whatever drug they are compared with. They tend to work better when pain is severe and in a patient who is anxious. The down side is that, over time, a placebo becomes less effective (Melzack and Wall, 1988). [177.44] Psychological Factors When psychological factors are an important part of the pain experience - not an uncommon circumstance - invasive treatment may make the situation worse. But pain must not be assumed to be purely psychological unless physical illness has been carefully ruled out. The physical and psychological aspects of pain often interact in complex ways. Among the many factors that may have to be taken into account are the patient's expectation of the final outcome, past experience with pain, ethnic or cultural attitudes toward pain and its treatment and ''secondary gain'' - effects of pain (such as not working or receiving attention) that the patient may welcome (Aronoff, 1992).
[177.45] Treating Pain in Children It often is assumed that a child's pain is, in a direct way, proportional to the nature of disease or injury and how much tissue damage has taken place. This view is incorrect, however. Pain in children seems to be even more plastic than in adults. How often pain is adequately relieved in children is far from clear. Opioids should not automatically be forbidden to children. Issues of safety are, however, paramount. It is helpful to design treatment programs aimed at specific conditions afflicting children, such as cystic fibrosis, sickle cell disease and cancer (Waldman and Winnie, 1996). [177.46] Treating Pain in the Elderly To assess how older persons are responding to treatment for pain, it may be necessary to use simpler measures and to repeat assessments at frequent intervals. This is especially important for those who are cognitively impaired, and for all elderly patients who undergo major surgery. Pain management should be re-evaluated when an elderly patient is discharged home or goes to a nursing home. Older patients very often are taking many drugs, and so are at risk of adverse drug interactions. Nonsteroidal anti-inflammatory drugs (NSAIDs), though effective, are especially likely to cause physical or mental side-effects in the elderly. Older persons tend to be sensitive to the pain-relieving effect of opioids, and so may require lower doses. In general, treatment should start with a low dose and be carefully adjusted to the clinical response (NCI, 1996). FOOTNOTES: Footnote 4. See also ch. 178 for a detailed discussion of the psychiatric aspects of pain. P 177.50 DRUG TREATMENT The three basic groups of drugs used to relieve pain include, firstly, nonnarcotic analgesics such as aspirin and acetaminophen. Aspirin is one of a large number of nonsteroidal anti- inflammatory drugs (NSAIDs), which effectively relieve pain that is not too severe. Secondly, there are the more potent narcotic drugs used to treat severe pain such as that caused by cancer. The opiates include morphine and drugs derived from morphine. The opioids are man-made drugs that resemble morphine in their chemical structure, and have similar effects. Thirdly, a wide range of drugs including antidepressants and muscle relaxants, do relieve some types of pain although they are not used primarily for this purpose. Finally, many attempts have been made to relieve pain by smoking marijuana or taking a drug that contains its active substance. [177.51] Nonnarcotic Analgesics Aspirin and acetaminophen are by far the most widely used of this class of painrelieving drugs. Probably more than twenty other nonnarcotic analgesics are widely prescribed. Some of the more familiar ones include ibuprofen, indomethacin, naproxen, diclofenac and phenylbutazone (Melzack and Wall, 1988).  Aspirin and Other NSAIDs
Aspirin, which chemically is acetylsalicylic acid, was developed along with many other drugs of this type in the late 1800s. Besides relieving pain, aspirin combats fever and suppresses inflammatory responses. The various NSAIDs differ in their ability to exert each of these effects. Which is prescribed may depend on the particular clinical circumstances. [a] Mode of Action NSAIDs relieve pain by their effects on the injured tissue itself, not the peripheral or central nerves. Relief of pain, fever and inflammation all are related to suppression of a substance called prostaglandin, which is released into injured tissues. It is these prostaglandins that sensitize the nerve endings to trigger pain messages. They also produce swelling, redness and other signs of inflammation. The NSAIDs not only inhibit the production and release of prostaglandins, but also counter the effect of bradykinin, another pain- producing chemical. NSAIDs also dilate peripheral blood vessels, which may lower the body temperature (Denson and Katz, 1992). [b] Uses Many clinical trials have shown that all NSAIDs are about equally effective. Most of them relieve pain about as well as a low dose of aspirin, 1 to 2 grams per day (Denson and Katz, 1992). Typical conditions treated by NSAIDs include arthritis, common headache, bone injury and sore muscles. They also are used after tooth extraction and some other minor operative procedures. Aspirin and other NSAIDs are generally given by mouth. Aspirin has a ceiling effect of about 1 gram (1,000 milligrams). That is, higher doses will not make them more effective (Aronoff and Evans, 1992). [c] Side Effects Because they are so widely used, aspirin and other NSAIDs are the major cause of serious drug side-effects. The commonest is irritation of the lining of the stomach and bowel. Aspirin also slows clotting of the blood. Together, these effects can cause serious gastrointestinal bleeding, especially in patients with an ulcer. Heavy drinkers who take aspirin to cure a hangover are especially at risk. Despite warnings and the availability of coated aspirin that slows its release into the bowel, many patients take too much of these drugs and suffer side-effects as a result. In fact, physicians today commonly advise their middle-aged male patients to take a low dose of aspirin on a regular basis to help prevent heart attacks (Denson and Katz, 1992).5 Clues that a person is overdosing with aspirin are trouble breathing easily, an irregular heartbeat, sudden trouble hearing clearly, a ringing in the ears (tinnitus), and nausea or vomiting. Tinnitus is a particularly reliable sign of toxicity from aspirin. Persons who have disorders of the gastrointestinal tract, liver or kidneys should avoid aspirin and other NSAIDs. The same applies to asthmatics. These drugs also should be kept from pregnant women and those with any type of bleeding disorder (Melzack and Wall, 1988).  Acetaminophen When aspirin and other NSAIDs are not tolerated for any reason, acetaminophen (also called paracetamol) is an option. Acetaminophen does no harm to persons who have an ulcer of the stomach or duodenum. It relieves pain as efficiently as aspirin, but lacks its anti-inflammatory effect and so does not help those with arthritis. Like aspirin, high doses of acetaminophen may seriously damage the liver (Aronoff and Evans, 1992).
[177.52] Narcotic Analgesics Nerve cells, both peripherally and in the brain and spinal cord, possess receptors for opiates on their surfaces. Ordinarily these receptors are occupied by enkephalins and endorphins, the body's own opiate-like substances. Narcotic agonists like morphine relieve pain by binding chemically to these opiate receptors. Narcotic antagonists bind to the same receptors and prevent agonists, either endogenous (in the body) or administered, from relieving pain. There also is a group of mixed agonist-antagonist drugs which have opposed effects on pain. Opioids are the major type of drug used to relieve moderate to severe pain. They are effective when used properly, and the proper dose can readily be determined. Unfortunately, many patients do not receive the benefits of narcotic therapy because physicians confuse the predictable effects of long-term treatment - tolerance and physical dependence - with the much feared psychological dependence, or addiction (NCI, 1996). The key in any case is to balance a given drug's ability to control pain against its potential adverse effects.  Agonists Most agonist-type narcotics are opiates, so-called because they derive from opium, an extract of the poppy plant. Both morphine and codeine are extracted from opium, and further changes in their chemical structure have yielded hydromorphone (Dilaudid (R)), oxycodone and heroin. Synthetic narcotics such as meperidine (Demerol (R)), fentanyl, and methadone and propoxyphene (Darvon (R)) are attempts to separate the pain-relieving effect of narcotics from their often serious side-effects. Among the many myths surrounding opioids are that there is a maximal safe dose, that addiction is inevitable and that all users eventually require larger doses. Further, it should be recognized that not all types of pain respond to opioid treatment, and that opioids do not always depress respiration (Caillet, 1993). [a] Site of Action In the midbrain, opiates activate descending inhibitory nerve paths that keep the spinal cord form transmitting pain messages. In the spinal cord, the same drugs prevent pain messages from passing from incoming nerve paths to the brain cells that perceive pain. Apart from their direct effects on transmission of pain signals, opiates produce euphoria, a feeling of profound well-being, and they reduce tension and fear. These effects can be very helpful to ill or injured patients who need to rest. But they may be gained at the cost of excessive drowsiness and difficulty thinking clearly. Narcotics also can promote blood flow by paralyzing the muscle tissue in vessel walls that keep the vessel constricted. This can increase blood flow to the heart after a heart attack, or to the brain after a stroke. [b] Clinical Use Opiates are called on most often when severe pain develops suddenly, as after severe injury or a heart attack. They also are used to control chronic pain from cancer and other serious illnesses, severe labor pain and postoperative pain. The stronger narcotics such as morphine and Dilaudid (R) are used only when nothing less will suffice. Moderate pain may respond to a weaker
narcotic such as codeine or oxycodone. Opiates may be given by mouth or by injection into a muscle or vein. Injection is the norm in any emergency situation. Because individuals may differ widely in how they respond to the same dose of narcotic, it is essential to individualize treatment. A regular dose schedule will prevent pain from recurring and avoid the need to have to overcome it each time. As a rule, doses are altered by one-fourth to one-half of the previous dose. If changing from oral treatment to injection, a lower dose will be needed. When and if pain resolves, opiate treatment should be gradually withdrawn to avoid withdrawal symptoms (NCI, 1996).  Antagonists and Mixed Agonist-Antagonists The best example of a narcotic antagonist is naloxone, which totally blocks the action of morphine. As such, it is used to treat morphine overdose. The so-called mixed agonist-antagonist drugs, such as nalorphine and pentazocine (Talwin (R)), activate some opioid receptors while blocking (or not affecting) others. These agents are used mainly to relieve postoperative pain. They are avoided in patients with long-lasting pain because they may produce psychotic changes, and can trigger withdrawal symptoms in patients who are dependent on another narcotic.  Recent Narcotics Research Current research has attempted to produce chemicals resembling enkephalins, the body's own narcotics, so as to relieve pain while avoiding side-effects. One form of enkephalin has been used in lieu of morphine (Melzack and Wall, 1988). Current work in this area also focuses on better ways of managing narcotic withdrawal symptoms and new approaches to helping those who have survived serious illness but become psychologically dependent (addicted). Work also is being done on refining narcotic delivery systems for use in particular circumstances.  Side Effects of Narcotics Opiate receptors are found throughout the body, not merely in neural tissues. This explains the wide range of side-effects that can occur. Tolerance, if viewed as a side-effect, occurs when the period of relief shortens progressively and increasing doses of narcotic are needed. Either other drugs may be substituted, or a different approach such as a nerve block or neurosurgery may be tried. Respiratory depression is the most feared side-effect of narcotics, and the commonest cause of death from an overdose of morphine. The opiate antagonist naloxone is an effective treatment for depressed breathing. Some narcotics may produce nausea or vomiting, but patients often are relieved by changing to a different drug. Constipation also can result from narcotic treatment. Cathartics and stool softeners may help, as well as the right type of diet. Patients given narcotics may become drowsy and mentally confused. The answer often is to give smaller, more frequent doses or to give a shorter-acting narcotic. Alternatively, the narcotic may be combined with an amphetamine for its stimulating effects. Miscellaneous narcotic side-effects include dizziness, suppression of the cough reflex and muscle spasms (especially from Demerol (R)).
The mixed agonist-antagonist narcotics may cause serious psychiatric symptoms such as depression and hallucinations. Patients may have nightmares and experience a sense of unreality. When occurring postoperatively (when these drugs tend to be used), these symptoms may be relieved by naloxone. [177.53] Adjuvant Drugs Apart from NSAIDs and narcotics, a variety of other (adjuvant) drugs may help relieve pain even if this is not their prime clinical use. Adjuvants include drugs with psychiatric effects (psychotropic drugs), See also ch. 106. anticonvulsants (used to treat seizures), steroid drugs, muscle relaxants and a miscellaneous group including antihistamines and amphetamines.  Psychotropic Drugs The major tranquilizers such as phenothiazine drugs are able to relieve both superficial and internal (visceral) pain in patients who have become tolerant to narcotics. (Minor tranquilizers such as the benzodiazepines Valium (R) and Librium (R) are not effective painkillers; they may even make pain worse). Persons who are depressed are less tolerant of pain and, with any condition causing pain, they require higher doses of analgesic drugs. A vicious cycle of pain, depression and insomnia may be very difficult to break. Tricyclic antidepressant drugs such as imipramine may be helpful in this situation. They can relieve pain independently of any improvement in the depression itself (Aronoff and Evans, 1992). Antidepressants also can help relieve pain from arthritis, migraine and the neuralgia that follows herpes infection.  Anticonvulsants When pain arises directly from diseased or injured nerves, as in trigeminal neuralgia (a severe type of facial pain), it may be relieved by drugs used to treat convulsions. They include carbamazepine (Tegretol (R)), phenytoin (Dilantin (R)) and valproic acid.  Steroids Steroid drugs such as prednisone and dexamethasone have antiinflammatory effects, and can relieve pain caused by acute inflammation. Steroids also can relieve pain from tumors in bone or nerve tissue. Chronic back pain may be eliminated by injecting a steroid into the epidural space between the spinal cord itself and its covering membrane. This is the case when pain results from inflamed nerve roots. Steroids also relieve neuralgic pain following herpes infection. A side benefit is that they counter the nausea and vomiting so often seen in patients given narcotics.  Muscle Relaxants Many pain states are accompanied by muscle spasm. Both injury and inflammatory diseases can cause abnormal muscle contractions which may be very painful. Muscle relaxants such as baclofen may relieve pain by altering how it is perceived in the brain. These drugs are generally well tolerated, and cause few side-effects (Gallagher, 1994).  Other Adjuvants Amphetamines, which stimulate the central nervous system, can increase pain relief when used along with narcotics. They also are used to reduce the dose of narcotic and thereby its sedative effect. Antihistamines such as hydroxyzine also are used in conjunction with narcotics. They augment pain relief, lessen anxiety, and also have antiemetic (prevent nausea) effects. Sedatives, hypnotics, and anti-anxiety drugs occasionally are noted to relieve pain, but the effect is not striking and it is hard to separate this effect from the other clinical
actions of these drugs (Haddux, 1992). [177.54] Marijuana (Cannabis) Marijuana is the leaf of an easily cultivated plant, Cannabis sativa. Recreational users nearly always smoke marijuana (''pot'' and ''grass'' being common colloquial terms) in the form of a cigarette, or ''reefer.'' Rarely, though, it is chewed and eaten. The active chemicals derived from cannabis leaves are known as cannabinoids. The one used most often both for experimental purposes and in the clinical setting is known chemically as delta-9-tetrahydrocannabinol (THC). THC is taken orally as tablets of dronabinol (Marinol (R)).  Background Painful states always have been featured on the long list of conditions that putatively benefit from smoking cannabis. The use of cannabis for pain relief has been documented since ancient times. In the 19th century hemp was officially welcomed into the pharmaceutical repertoire both in Europe and America. It was marketed by major pharmaceutical companies in numerous forms available over-the-counter as well as by prescription (Robinson, 1996). A century ago, cannabis was second only to the opiates as a means of controlling chronic pain. Its mood-elevating properties were welcomed, as they seemed to enhance the relief of pain. Specific conditions for which cannabis products were used included migraine headache, a very severe form of facial pain called tic douloureux and other neuralgic disorders. Cannabis also was widely used as a topical anesthetic and to lessen the pain of childbirth (Mikuriya, 1994). Cannabinoids were censored from the U. S. Pharmacopoeia in 1942. In 1950 the Merck Index, a comprehensive list of accepted pharmaceutical agents, deleted its listing of cannabis.  Mode of Action When rats were given a synthetic cannabinoid, and at the same time pressure was applied to the hind paw to a degree that usually caused a painful response, the nerves in the spinal cord that convey pain signals stopped firing. This is direct evidence that cannabinoids can inhibit pain transmission in the spinal cord (Hohmann, et al., 1995). Another study identified specific receptor sites by which cannabinoids can attach themselves to nerve cells. In this way they might be able to mimic natural body compounds that regulate nerve signaling for mood, memory, movement and pain perception (Mackie and Hille, 1992). Finally, when pregnant rats received THC, it had the effect of altering pain sensitivity in their offspring. This probably resulted from the cannabinoid interacting with opioids naturally present in the brain (Vela, et al., 1995).  Clinical Use Studies and observations of how cannabinoids affect pain in humans entail certain problems not encountered with most other types of drugs. Firstly, how they are given seems to make a considerable difference. Those who habitually smoke marijuana often claim greater pain relief than when given tablets of THC. In contrast, some clinical studies suggest just the opposite, but these subjects often are thought to be ''naive,'' lacking past experience with the drug.
A second problem is that clinical studies of pain rely on participants reporting the point at which pain begins during stimulation, or ends when a painful stimulus is removed, an entity known as the threshold. The double-blind study design, in which neither the experimenter nor the subject knows whether active drug or a placebo has been given, is supposed to assure objectivity. But the psychoactive effects of cannabis (euphoria, clouded consciousness, a ''fuzzy'' or distanced feeling) may allow subjects to ''peek through the double-blind,'' rendering their responses unreliable (Clark, et al., 1984). [a] Indications for Use Today cannabis is probably used most widely to relieve chronic pain from cancer, and in patients with AIDS who may suffer from a number of painful conditions. In addition, cannabinoids are sometimes used to lessen pain from very severe arthritis, combat migraine headache and relieve intolerable itching in patients with inflammatory skin disorders (Robinson, 1991). When 57 San Franciscans, most of them HIV-positive, were interviewed at a cannabis buyers' club and asked their reasons for using cannabis, 22 mentioned arthritis and other forms of pain, and 11 cited migraine or vascular headache. Several of the aforementioned purchasers mentioned that they smoked marijuana as a substitute for drinking or for using opiates or sedatives. A study from the early 1940s found that patients attempting to stop using an opiate did better when they replaced it with a cannabis derivative than when they simply tried withdrawing, either suddenly or gradually. They reportedly experienced less marked withdrawal symptoms, felt much better, and were able to return sooner to their work (Grinspoon, 1994). [b] Effectiveness Results from a series of studies conducted in the 1970s run the gamut from an impressive rise in pain tolerance to an actual increase in sensitivity to painful stimuli. Marijuana smoking did augment pain tolerance in one double-blind investigation. In another study, a series of cancer patients gained relief from orally administered THC, but a competing trial failed to confirm this finding. Two independent studies found that both THC and smoked marijuana made normal subjects more sensitive to pain when their fingers were stimulated electrically. (This should not be unexpected, as marijuana smokers often report that they feel all manner of stimuli more acutely, a form of ''heightened consciousness.'') The overall conclusion from these studies is that any analgesic effect of THC is not consistent enough to recommend its clinical use (Nahas, 1984). Another series of studies from the same period were well-controlled trials comparing cannabinoids with analgesics. Good pain relief was the rule but, as in many of the previously cited studies, it often was accompanied by euphoric feelings and a wide range of side-effects. Again, the overall conclusion was that cannabinoids cannot be routinely recommended explicitly for treating cancer pain (Raj, 1992). [c] Side-Effects Although euphoria and other aspects of ''getting high'' may be purposefully sought by recreational users of cannabis, from a clinical standpoint they must be viewed as side-effects. Apart from these so-called psychoactive actions, marijuana users (and subjects in experimental studies who receive THC) frequently become drowsy and develop a slow heartbeat and low blood pressure. How and whether cannabis affects the brain is perhaps the greatest concern. A recent survey, covering both volunteer subjects given known amounts of cannabis
and habitually heavy users, showed that there are in fact residual effects on shortterm memory, attention, and the ability to perform tasks requiring clear thinking and coordination. These effects generally last from 12 to 24 hours after exposure. Whether some users may have more persistent changes remains uncertain (Pope, Jr. et al., 1995). An extensive review of the literature suggests that using cannabis heavily on a regular basis may impair the ability to process information. There is, however, no firm evidence that the brain is irreversibly damaged (Castel and Ames, 1996). The U.S. Pharmacopeia warns against giving THC to pregnant women (because studies suggest the fetus is at risk), or to lactating women (as cannabis passes into the breast milk). It also cautions against using THC along with agents (including alcohol) that depress the central nervous system, or with the tricyclic antidepressant drugs used to treat depression. Finally, THC can worsen the symptoms of heart disease, and may aggravate schizophrenia or manic-depressive illness (U.S. Pharmacopeia, 1994).  Prospects The National Institute on Drug Abuse has convened a panel of 8 experts to recommend studies that will clarify the clinical uses of marijuana. Their proposals will be subject to approval by the director of the National Institutes of Health. The panel is expected to recommend that controlled studies should in fact be carried out. The panel asserted that among the medical uses of cannabis to be considered is alleviating the suffering of patients with severe pain. Whether to study the effects of smoked marijuana or THC remains an open question. The present position of the Food & Drug Administration (FDA) is that no drug has to be demonstrably better than existing agents - or even as good - in order to be approved (New York Times, 1997). [177.55] Drug Combinations It is very often possible to afford the patient greater relief from a combination of drugs than is possible with a single type of drug. For instance, an analgesic acting locally to stop the release of prostaglandin (such as an NSAID) may be combined with one (possibly an opioid drug) that inhibits pain perception in the central nervous system. When ongoing narcotic treatment is supplemented by a nonnarcotic drug, the patient benefits without having to raise the dose of narcotic. Another advantage of using drugs that work differently is that the risk of side-effects is reduced. Drug combinations that have proved helpful include codeine plus aspirin, and adding a small dose of desipramine, an antidepressant, to morphine. Using dextroamphetamine (''speed'') along with morphine is a very effective means of relieving pain from cancer, despite their reputation as ''street drugs.'' A three-drug regimen for resistant cancer pain could include the opiate methadone, the antidepressant amitriptyline and a nonnarcotic analgesic (Melzack and Wall, 1988). Combining a potent codeine derivative such as hydrocodone or oxycodone with acetaminophen helps control postpartum and postoperative pain. Propoxyphene, a relatively weak narcotic, works much better when combined with aspirin or acetaminophen. There currently is interest in adding a weak opioid to NSAID treatment when this by itself does not adequately relieve pain (Beaver, 1992). [177.56] Delivery Systems
Customarily, pain-relieving drugs have either been taken by mouth or injected into a muscle. New ways of administering analgesics can make them more effective while at the same time limiting their adverse effects. Patients may be spared the discomfort of repeated injections - a considerable boon for those who need long-term or indefinite treatment. Patients who vomit easily can receive drugs rectally. Some drugs, such as fentanyl, may be given transdermally (through the skin), although it is difficult to find the proper dose (NCI, 1996).  Slow Release Preparations Morphine may now be given in the form of an implanted pellet whose coating releases the active drug over a period of 8-12 hours. This allows patients to sleep through the night.  Continuous Infusion When a patient cannot take a narcotic by mouth for any reason and refuses (or cannot tolerate) repeated intramuscular injections, the drug may be given continuously (infused) either intravenously or beneath the skin surface (subcutaneously). If a patient needs long-term treatment, a pouch may be easily implanted under the skin. A timer mechanism releases the drug at the desired rate into a tube leading to the spinal cord or the brain itself. The pouch can be refilled by simply injecting drug through the skin.  Spinal Administration of Morphine Giving an opioid directly into the spinal canal is an effective means of controlling postoperative pain as well as severe cancer-related pain. The drug may be injected or infused into the space separating the membranes covering the spinal cord and the cord itself. The great advantage of this approach is that motor and sensory functions are unaffected. The patient is able to walk without the danger of sudden low blood pressure - a risk when a local anesthetic is used. Spinal opioid therapy is especially useful in elderly patients, those who are very obese, and those whose heart and lung function is compromised (Rawal, 1996). In addition, little narcotic reaches the brain, so that patients are not excessively sedated or confused. Morphine has a stronger effect when given spinally rather than intravenously, and its effects last longer. There is, however, always a risk of injuring the spinal cord, suggesting that this method be used only when it has very definite advantages.  Patient-Controlled Analgesia-Postoperative patients who wish to avoid repeated injections to control pain can take partial control of their own treatment. With patient-controlled analgesia (PCA), the patient is able to deliver small amounts of morphine or another analgesic, up to a limit and at specified intervals. The injection itself can be subcutaneous or into a muscle or vein, although the intravenous route is most convenient. When the patient is able to take oral analgesia, the physician can learn how well it is working by noting how much PCA the patient is using (PHS, 1992). FOOTNOTES: Footnote 5. See also ch. 30. P 177.60 NERVE BLOCKS When the cause of pain cannot be corrected and drugs fail to control it, other approaches are possible. One of them is the nerve block, which generally uses a drug such as a local anesthetic to stop the transmission of pain signals along those nerves
responsible for the pain. A more drastic type of nerve block is to use a neurotoxic substance to permanently destroy a nerve (neurolysis). A nerve block may also help when a patient does respond to drugs, but requires doses so large that they seriously interfere with the patient's activity or mental function.6 Another use of the nerve block technique is for diagnosis: to determine the exact origin of pain in a particular patient. This is done by surrounding (infiltrating) the suspect nerve with a local anesthetic to see whether pain ceases. The effect is intended to be a temporary one. A nerve block also may be used prognostically, to predict the outcome were a nerve to be destroyed. Finally, when a procedure is planned that may lead to some painful state such as causalgia, a nerve block may be given ahead of time to forestall pain (NCI, 1996). [177.61] Indications and Selection of Patients A nerve block, whether temporary or permanent, should be viewed as part of a range of treatments that can help a patient cope with pain. Any physical measure such as a nerve block must not ignore the behavioral and psychosocial aspects of the patient's condition and how they relate to the pain that is experienced. The success of neural blockade will depend on the patients ability to estimate the severity of pain and how it is changing during the procedure. A diagnostic nerve block can help distinguish between pain of somatic and psychogenic origin. (Wurm, 1992). A nerve block can effectively control either acute or chronic pain. In patients with acutely painful conditions, the block will temporarily cut off the source of pain from where it is consciously perceived. A bone fracture and dental surgery are good applications. Although nerve blocks may be less dramatically effective in relieving chronic pain, they still may have considerable diagnostic and even therapeutic value. If neurosurgery is being considered to permanently ablate the source of pain, a temporary block will inform the patient of what may be expected and help in making the decision of whether to operate (Raj, 1992). Nerve blocks are avoided in patients who have a bleeding problem or are on anticoagulants, and also in those with infection in the region. Poorly localized pain seldom responds to neural blockade. Patients dependent on narcotics are not good candidates. A nerve block may not be feasible if the patient cannot tolerate the pain of the procedure itself without receiving an analgesic. If a patient clearly has psychogenic pain, a nerve block will not be helpful (Wurm, 1992). [177.62] Mechanism of Action Neural blockade is intended to halt the transmission of pain messages to the brain. A small area of localized pain may be abolished by blocking the peripheral nerve serving the area. More diffuse pain requires a block closer to the spine - the site where all peripheral nerves converge.  Local Anesthetics The nerve impulse actually is a wave of electrical energy spreading along the extended part of the nerve, the axon. Anesthetics abolish pain by blocking this wave, or action potential. Usually a local anesthetic is injected directly into the nerve, but it may also be injected (infiltrated) into the area surrounding the nerve. Unlike cocaine, the original local anesthetic, its successors (lidocaine, procaine, etc.) halt pain
impulses without causing mental effects. Using a small amount of anesthetic it is possible to block, say, sympathetic nerve fibers (those controlling many organ functions) without altering nerve transmission in sensory or motor nerve fibers. This makes it possible for a patient to remain active without suffering musculoskeletal pain. [a] Epidural Infusion A local anesthetic may be injected continuously (infused) through a catheter placed in the epidural space surrounding the spinal cord. Bupivacaine is often used for this purpose. The anesthetic stops pain transmission in the nerve roots to abolish pain in the legs, pelvis, abdomen or chest, depending on the spinal level where the injection is made. Epidural infusion of a local anesthetic is a very effective way of controlling labor pain. It also is used diagnostically in an attempt to relieve low back pain spreading to the legs (sciatica). [b] Side Effects Unless special techniques are used, a nerve block generally paralyzes the area injected as well as relieves pain. If a local anesthetic is given for too long a time, it may damage the nerve. Rarely a patient will suffer an allergic reaction to a local anesthetic. Too high a dose can affect the brain and cause convulsions. Local anesthetics can impair the electrical activity of cardiac nerves and thereby keep the heart from functioning normally. Newer local anesthetics that will not affect the heart are being developed (de Jong, 1996).  Neurolytic Agents Neurolysis (literally, lysing or killing a nerve) is an aggressive measure used, for instance, to relieve cancer pain that is resistant to even potent narcotics. It also is used in some patients with severe neuralgia or pain from occlusion of blood vessels, and when neurosurgery is not possible for any reason. Alcohol and phenol are often used for neurolysis, as they destroy nerve proteins and the myelin sheath that covers and protects the nerve axon. It is important to get the material as close as possible to the target nerve. A nerve also may be destroyed by freezing (cryoanesthesia), by alternately freezing and thawing the nerve or applying radiofrequency energy. When alcohol is used for neurolysis, very painful neuralgia may complicate the procedure. The area served by the treated nerve may be numbed for a time, but usually this resolves fairly quickly. When a neurolytic agent is injected into the lower part of the spinal column, bowel or bladder function may be lost (Jain and Gupta, 1996). [177.63] Diagnostic Nerve Blocks A local anesthetic block is ideal for demonstrating just which nerve, or nerves, are responsible for a patient's pain. A block can indicate whether pain is arising from the body surface, an internal organ, or a site in the central nervous system. Exclusion of all these possibilities might suggest psychogenic pain (but cannot establish it with certainty). A neural block is helpful when neurolysis or neurosurgery is planned. It may indicate how effective the more invasive treatment will be. It also can show whether new pain develops elsewhere in the body. If this in fact happens, neurolysis or neurosurgery might better be avoided (Wurm, 1992). [177.64] Therapeutic Nerve Blocks
Either temporary nerve block with a local anesthetic or neurolysis, permanently destroying a nerve or nerves, may be used to relieve pain.  Local Anesthetic Block It is common to administer a series of temporary nerve blocks to patients with chronic pain. Used with other appropriate measures, the blocks can provide long-lasting relief, especially when muscle spasm is part of the problem. Many painful conditions involve a cycle of increased muscle tension, poor posture, immobility and pain. Injecting anesthetic into a trigger point can break the cycle (Wurm, 1992). Other indications for local anesthetic nerve block are reflex sympathetic dystrophy (a chronic post-injury disorder caused by degenerating sympathetic nerves), neuralgia, postoperative pain and phantom limb pain. In patients with cancer-related pain, it is worth trying neural blockade before proceeding to neurolysis. Infusing an anesthetic epidurally can relieve severe pain from cancer in the pelvic region.  Neurolytic Blocks Pain may be relieved for as long as a year after neurolysis, but the average time is less than a month. For this reason, and because of the risk of side-effects, neurolysis often is used when less invasive measures have failed to relieve cancer- related pain and when life expectancy is limited. Pain resulting from interruption of an afferent nerve is not helped by neurolysis. Somatic nerves rarely are lysed for reasons other than cancer (Wurm, 1992).  Common Nerve Block Procedures Among the commonest sites for neural blockade are the stellate ganglia (groups of nerves in the neck and chest), lumbar sympathetic ganglia in the lower back and the celiac plexus (a mass of ganglia in the region of the pancreas). [a] Stellate Ganglion Block Sympathetic ganglia in the upper chest and lower neck may be blocked to relieve pain from reflex sympathetic dystrophy following injury in this region. Pain from whiplash injury is commonly managed in this way. A stellate ganglion block can also relieve pain caused by herpes zoster and tumors in the upper part of the lung. Other indications are Raynaud's disease (a disorder of the sympathetic nerves controlling blood vessels), and pain arising from a clot (embolus) lodging in a blood vessel of the arm (Raj, 1996). [b] Lumbar Sympathetic Block Burning pain in the lower legs resulting from a deficient supply of oxygenated blood is a prime indication for neural blockade at this level. A lumbar block also may relieve posttraumatic reflex sympathetic dystrophy in the legs, pain arising from disease of the pelvis or ureter (the tube conducting urine from the kidneys) and pain arising from an amputation stump or phantom limb. Renal colic is one of the most severe forms of pain, and can be relieved by neural block in the area of the second to fourth lumbar vertebrae, the area of the loin (Stanton-Hicks, 1996). [c] Celiac Plexus Block The celiac plexus, a mass of sympathetic ganglia near the first lumbar vertebrae, may be blocked by inserting a needle into the flank. It can relieve pain from pancreatic cancer, which may be extremely severe. This block also can help tell whether pain is arising in an organ like the pancreas or from the abdominal wall (Wurm, 1992). Recently temporary leg weakness was described as a complication of blocking the
celiac plexus with alcohol (Wong and Brown, 1995). [d] Other Nerve Blocks Injecting anesthetic into the subarachnoid space surrounding the spinal cord may relieve severe pelvic pain caused by cancer. It may prove helpful to block a specific nerve root when the origin of limb pain is not clear or if pain may result from disease of an intervertebral disk. Injecting specific intercostal nerves can show just which of them have been injured (from an accident or chest surgery). Pain caused by injury to various somatic nerves, such as the greater occipital nerve of the scalp or the lateral femoral cutaneous nerve in the thigh, can readily be blocked by injecting a local anesthetic (Rybock, 1994). [177.65] Nitrous Oxide The very first inhaled anesthetic, nitrous oxide (''laughing gas'') is becoming an increasingly popular analgesic. Inhaled through a face mask, it can control pain from minor surgery (such as dental extraction) or procedures such as spinal puncture. At the other end of the scale, patients with terminal cancer may control episodes of pain by inhaling nitrous oxide from a small tank kept at hand. When a woman in labor does not want regional analgesia or it is unavailable, nitrous oxide may be a very acceptable substitute. Typically the woman herself administers the gas. It is cleared from the newborn infant in a matter of minutes (Eisenach, 1992). FOOTNOTES: Footnote 6. See also ch. 58 for additional information on nerve blocks. P 177.70 NEUROSURGERY When drugs fail to control pain and even neural blockade or neurolysis proves inadequate, the next step is a neurosurgical procedure. Traditionally a nerve or nerve pathway was severed at the proper point in order to stop the transmission of pain impulses. Virtually every part of the nervous system - peripheral and central has been cut (sectioned) in order to control unrelenting pain. Even when this works, however, the pain is likely to recur and may be even more marked than before (Freidberg, 1992). Conventional sectioning procedures still are used in some patients with intractable pain, especially those with advanced cancer who are not expected to live long. For many other patients, however, sectioning has been replaced by more refined methods of creating small, discrete lesions at any level of the nervous system. These procedures often can be done through the skin (percutaneously) under local or regional anesthesia, and they entail little blood loss. Another approach that sometimes relieves pain is to electrically stimulate rather than damage or destroy the pain-carrying nerve fibers (Melzack and Wall, 1988). [177.71] Radiofrequency Coagulation Discrete nerve lesions of limited extent may be produced by placing a needle into the target site and inserting an electrode through it. The nerve tissue is burn-damaged by heat from a high-frequency current. This technique can be applied to tiny brain sites through the use of stereotactic radiography. The head is rigidly fixed in place, and a system of coordinates is used to map the site where a target lesion is to be
made. In most cases a series of small lesions are used to ablate pain-transmitting nerve tissue. The patient remains conscious so that the surgeon is able to gauge the effect of each lesion before placing the next one. [177.72] Peripheral Lesions Cutting a peripheral nerve, known as peripheral neurectomy, generally relieves pain only when a particular nerve (and no other tissues) is involved by a tumor. Pain in the chest wall caused by an invading tumor may be relieved by cutting one or more intercostal nerves, those running alongside the ribs. With these exceptions, cutting several peripheral nerves usually fails to relieve pain and may instead produce numbness or feelings of burning and tingling (Freidberg, 1992). [177.73] Spinal Root Lesions When pain results from cancer or other disease in the chest, pelvis or spinal column, cutting peripheral nerves will not help. Instead, the spinal root, where peripheral nerve fibers come together to enter the spinal cord, is sectioned (cut). All sensation including pain travels through the dorsal (sensory) root. Leaving the ventral (motor) root intact will avoid paralysis or muscle wasting. The downside is that all sensation, not only pain, is abolished when the dorsal root is cut.  Multiple Lesions Any dorsal spinal root contains nerve fibers from overlapping areas of the body. For this reason, at least three roots have to be treated to assure that pain in any one part of the body will be relieved. The usual procedure is to inject a nerve- damaging substance into the proper region of the spinal cord, and then turn the patient so that only the nerve roots on the affected side are damaged. This is a common treatment for patients who have cancer in the pelvis (Melzack and Wall, 1988).  DREZ Lesions Patients with severe pain from post-herpes neuralgia or from tearing (avulsion) of peripheral nerves or nerve roots themselves may be relieved by cutting the dorsal nerve root where it enters the spinal cord. This point is termed the dorsal root entry zone (DREZ). Avulsed spinal roots should be confirmed by contrast (dye) radiography (myelography) before proceeding. Today many patients suffer damaged nerve roots in the upper (cervical) spine as a result of a motorcycle, auto or snowmobile accident. Formerly the affected nerve roots were simply sectioned. A more refined approach is to expose the involved area of spinal cord and produce a group of tiny thermal radiofrequency lesions in the dorsal surface of the spinal cord itself (the dorsal horn). If other parts of the cord are avoided the desired effect will be achieved without serious side-effects (Nashold, Jr. et al., 1994). Use of a laser attached to an operating microscope to make the lesions may be even safer (Powers et al., 1988).  Rhizotomy Strictly speaking, rhizotomy refers to surgical cutting of a nerve or nerve root. Formerly this was done as an open operation, but long-term success rates were as low as one in five patients. Removing the ganglion (a collection of nerve cells) is only slightly more effective. Today rhizotomy is done percutaneously by injecting alcohol into the nerve tissue, or by using a radiofrequency current to damage it thermally. This procedure does carry a risk of impairing motor or sensory function (Coffey, 1992).
 Treatment of Trigeminal Neuralgia The trigeminal nerve is one of the major cranial nerves serving large areas of the face. Neuralgia at this site is the commonest pain disorder of the head/neck region that is treatable surgically. The goal is to damage the nerves ganglion (the gasserian ganglion) either by radiofrequency coagulation or injecting glycerol. Another option is to inflate a small balloon at the end of a catheter to compress the nerve. All these techniques now may be done through the skin by inserting a needle through an opening in the base of the skull. Neuralgias affecting other cranial nerves may be managed in the same way (Coffey, 1992). Open surgery to relieve pressure on the ganglion is seldom performed today. The pain commonly returns, and normal sensation may be impaired (Melzack and Wall, 1988). [177.74] Cordotomy Cutting the spinothalamic tract of the spinal cord, a major nerve pathway leading to the thalamus of the brain, is used especially to relieve pain localized to one side of the body below the shoulder level. The thalamus is an important relay site sending pain signals to other parts of the brain. If life expectancy is less than one year, cordotomy is often strongly considered. If desired, the cord may be cut at a level that preserves feeling in the upper limb but relieves pain in the lower chest, abdomen and lower extremity. Either an open technique may be used, or cordotomy can be done percutaneously using radiofrequency current. This operation must be avoided in any patient who has trouble breathing. Pain is relieved after a successful cordotomy and temperature sensation is lost, but the patient still has feeling in the skin and retains normal motor function. When combined with drugs and other measures, as many as 90 percent of patients have good to excellent initial results. But pain relief tends to lessen as time passes, which is why cordotomy is not advisable for those whose cancer may permit long-term survival. Some patients develop uncomfortable feelings (dysesthesias), or actual pain ''mirrored'' at the same site on the opposite side of the body (Rosen, 1996). Another spinal cord operation, commissural myelotomy, uses an incision in the lower spinal cord to relieve pain in the pelvic region. Leg weakness and other complications are frequent, however, even when the surgery is done using a microscope (Freidberg, 1994). [177.75] Cerebral Operations Often the last resort for relieving intractable pain is to cut nerve paths in the brain itself. Lesions at certain regions in the central part of the brain (mesencephalon), the thalamus, and a part of the limbic system called the cingulum that is important in pain perception. Damaging the pituitary gland also may prove helpful in some cases.  Mesencephalic Tractotomy This procedure no longer is done to interrupt the spinothalamic fibers, those severed at cordotomy, at the level of the midbrain. Its mortality is very high, and many surviving patients develop dysesthesias that can be worse than the initial pain (Melzack and Wall, 1988). It is, however, possible to make discrete radiofrequency lesions at this level to relieve pain on one side of the head or neck. Using the stereotactic radiographic method the surgeon can be sure that only pain-transmitting fibers are damaged (Bosch, 1991).
 Thalamotomy Stereotactic methods also may be used to produce small lesions in the thalamus, where pain fibers from the spinothalamic tract of the spinal cord converge. Cancer patients with chronic pain on one side of the body often gain relief from unilateral thalamotomy. In those who do not respond, lesions may be made on the other side with little added risk (Freidberg, 1994).  Cingulotomy In earlier years an operation called lobotomy was done to cut fibers connecting the cerebral cortex (the outer covering of the brain that controls intellect and personality) with the rest of the brain. It did not actually relieve pain but was intended to lessen the anxiety and depression that often accompanies it. Unfortunately lobotomy also tended to seriously damage the patient's personality and ability to think. A modern substitute for lobotomy is cingulotomy. Lesions are made stereotactically in the cingulum (a central brain structure close to the fibers connecting the two cerebral hemispheres). The cingulum is part of the limbic system, which has a role in both pain and behavior. When successful, cingulotomy can abolish some of the negative emotions emanating from severe pain without substantially altering the patient's personality. Nevertheless, the procedure is seldom performed in the US because of a strong bias against lobotomy and other so-called ''psychosurgery'' (Freidberg, 1992).  Pituitary Gland Surgery While not part of the brain proper, the pituitary gland is a gland at the base of the brain that produces a number of hormones, some of which support the growth of some cancers. When cancer has spread to the bones it can cause excruciating pain that can seriously disrupt the patient's life and activities. Damaging the pituitary by applying heat or injecting alcohol can bring much needed relief to patients whose cancer has spread to multiple skeletal sites. Some cancers not dependent on pituitary hormones also may respond (Augustinsson, 1996). [177.76] Lesions of the Sympathetic System The sympathetic nervous system (part of the autonomic, or ''automatic'' nervous system) consists of chains of ganglia (nerve cell bodies) running along the spinal cord. Sympathetic nerves send signals to and from the internal organs, glands and blood vessels. Because these nerves release adrenaline (a substance that activates injured sensory nerve fibers) lesioning these fibers may sometimes relieve pain. In addition, noradrenaline constricts blood vessels, and limited blood flow to muscle tissue (including the heart) may cause pain (Melzack and Wall, 1988). Destroying the sympathetic ganglia by injecting alcohol or phenol often helps lessen the burning pain of causalgia that follows injury of a peripheral nerve. Lumbar sympathectomy has relieved painful causalgia of the lower extremity as well as pain caused by constricted blood vessels. A repeat procedure is sometimes needed. If done on both sides, lumbar sympathectomy can impair ejaculation in males (Coffey, 1992). [177.77] Neurostimulation There are two problems with the idea that merely cutting a nerve or nerve pathway will prevent pain messages from reaching the brain. It may in fact act like a nerve injury, activating the cut ends of the nerve cells to fire and causing deafferentation
pain. In addition, the nervous system can undo the effects of destructive nerve surgery by reorganizing its paths so that the pain signals will ascend to the brain via a different route. An alternative is to electrically stimulate rather than destroy central and peripheral nerves. Electrostimulation may be especially useful for patients who resist analgesic drugs. It may be done surgically or using electrodes on the skin surface (transcutaneous electrical nerve stimulation, or TENS). With reference to the gate theory of pain, electrostimulation may act by activating mechanisms that normally inhibit pain impulses, thereby ''closing the gate.''  Technique For electrostimulation an electrode is implanted in the appropriate part of the nervous system and attached to a wire leading to an implanted radio receiver. The patient can begin stimulation, and control its intensity, by holding the antenna of an external radio transmitter over the site of the receiver. Electrodes with multiple contact points now are available to provide stimulation at just the right points. Perhaps two of three patients with resistant chronic pain will respond to modern forms of electrostimulation (Racz, et al., 1992).  Stimulation of Dorsal Column of Spinal Cord The dorsal columns of the spinal cord, carrying the pain fibers, are the commonest target site for electrostimulation. It no longer is necessary to remove bony tissue from the spinal column to implant electrodes. A set of electrodes may be placed using a needle, anchored in place, and activated by an implanted pulse generator that can be externally programmed. Many patients with low back pain in whom surgery has failed have responded to electrostimulation of the dorsal columns (North, 1994).  Stimulation of the Brain Electrical stimulation of deep brain structures is generally used in two groups of patients. Electrodes are placed in the thalamus in patients with deafferentation pain caused by interruption of a nerve. They include patients with phantom limb pain, spinal cord injury, lesions of the brachial nerve plexus of the upper extremity or the lumbosacral plexus of the lower limb and neuralgia following herpes infection. Patients with chronic low back or leg pain and some who have noncancer pain in the abdomen or perineal region may respond to electrostimulation of neural tissue surrounding the cavities (ventricles) of the brain (North, 1994). Electrodes are implanted under local anesthesia, using a stereotactic radiographic technique. Test stimuli are delivered and the awake patient is asked for a response. When a tingling sensation replaces the customary pain, the electrode is correctly placed. After further testing to learn the correct voltage and frequency of stimulation, the electrode is attached to a receiver implanted in the chest wall. Occasionally the procedure is complicated by bleeding into the brain (which may be fatal) or infection (Melzack and Wall, 1988).  Tolerance Patients tend to build up tolerance to electrostimulation of either the spinal cord or brain, requiring stimulation at progressively higher levels and for longer periods. This tolerance may be avoided, or delayed, by limiting stimulation to no more than 20 minutes three or four times a day. The drug L-dopa, used to treat Parkinson's disease, can greatly reduce tolerance in patients who require long periods of stimulation (Melzack and Wall, 1988). [177.78] Complications of Neurosurgery
A declining analgesic effect as time passes after neurosurgery is not, strictly speaking, a complication. A relatively few patients, however, will develop a new type of pain in the form of severe burning after cordotomy. This may be even worse than the initial pain and is very difficult to treat. It probably is caused by abnormal firing of hypersensitive spinal cord nerves following operative injury (Melzack and Wall, 1988). Some ablative neurosurgical procedures carry a risk of numbing the target area or of causing muscle weakness. Bladder dysfunction also is a possibility. Whenever a catheter system is placed within the spinal column there is a risk of infection (Byers, et al., 1995). [177.79] An Experimental Approach to Pain Control Recent laboratory studies suggest that pain is effectively reduced when tissue from the adrenal medulla (the central hormone-secreting part of the adrenal gland) is placed into the space surrounding the spinal cord. Tolerance did not develop. The hope is that such a ''biological pump'' could provide a limitless, locally placed source of pain-reducing substances. The method was tried in five patients with chronic pain, three of whom had substantial and long-lasting relief (Winnie, 1996). P 177.80 OTHER PHYSICAL METHODS A very broad range of relatively noninvasive physical methods of alleviating pain, particularly musculoskeletal pain, have long been available. Medical history tells of cupping and scarification, the latter being the practice of cutting the skin with blades. Heat and cold application are time-honored methods, and acupuncture itself is an age-old remedy for pain anywhere on, or within the body.7 More modern methods include passing an electric current through the skin, applying heat using ultrasound energy and injecting the ''trigger points'' that give rise to pain. Some of these methods work by causing pain in order to relieve it, a process long known as counterirritation and more formally termed hyperstimulation analgesia (Melzack and Wall, 1988). Physical therapy is intended to correct any condition, such as poor muscle tone, spasm or weakness, that keeps a patient from functioning normally. With the correct method or combination of methods, the patient will in time gain confidence in being able to function better without suffering undue pain. Yeh and colleagues (1992) believe strongly that all patients with chronic pain should at least be evaluated by a physical therapist. Many medical professionals unfortunately place little value on the potential role of physical therapy. Through regular physical therapy a patient can learn what can be done to maintain function and prevent, or at least slow deterioration of his or her physical state. Physiatrists are medical doctors trained in physical medicine and rehabilitation, and are expert in distinguishing between pain and disability. The physiatrist is the logical choice to prescribe a comprehensive, team-managed rehabilitative program for patients with painful musculoskeletal disorders (Cole and Herring, 1994).8 Physical therapy may be delivered in an office or clinic, or at specialized rehabilitation centers. [177.81] Transcutaneous Electrical Nerve Stimulation (TENS)
The sensory nerves lying just beneath the skin surface can be stimulated in various ways using a battery-powered electric pulse generator and electrodes attached to the skin. TENS is widely considered to be very effective in relieving both acute and chronic pain, but just how it works remains uncertain. In terms of the gate theory, stimulation could interfere with the cycle of pain and muscle spasm by inhibiting nerves in the spinal cord that transmit pain signals. TENS also might directly depress the firing of damaged peripheral nerves. Generally the patient adjusts the frequency and strength of pulses until a tingling feeling is noted in the painful region. A lengthy trial-and-error process may be needed to determine the most effective type of stimulation. Apart from conventional high-intensity pulses, special modes are available (one of them resembling acupuncture stimulation) that may prove helpful in particular patients. The acupuncture-like mode of longer but fewer pulses at high intensity often relieves chronic pain. High-voltage galvanic stimulation may be helpful if there is prominent swelling in addition to pain. The electrodes may be placed over a trigger point, the spinal nerve roots or a dermatome (an area of skin supplied by branches of a particular spinal nerve). TENS has proved very helpful to patients with such conditions as rheumatoid arthritis, causalgia, and post-herpes neuralgia even when nerve blocks or neurosurgery have failed. Another application of TENS is to limit postoperative pain by attaching electrodes near the incision. In this way the patient may require less narcotic medication. TENS causes no serious side-effects, but it should not be used near a fetus in a pregnant woman or when a cardiac pacemaker is present (Yeh, et al., 1992). [177.82] Trigger Point Injections Pain following injury most often arises from myofascial structures including bone tissue, the muscle itself, tendon, ligament and other soft tissues. In fibrositis and fibromyalgia, both very common painful conditions, focal areas within a muscle can develop trigger points which can be felt as taut muscle bands that are tender when pressed on. Painful trigger points can limit motion of a body and, in time, cause it to weaken or waste away. Trigger points also may cause referred pain in a distant area.  Causes Chemical changes in injured tissues may produce a state of constant contraction, or spasm, accounting for the band of tight muscle tissue. In time acidic chemicals accumulate and sensitize nearby pain receptors. Another cause may be an increase in sympathetic nerve activity and noradrenaline release when nociceptors are sensitized. This itself further activates nociceptors in a cycle of continuous selfgenerated pain. The longer trigger points remain, the likelier it is that new ones will develop, resulting in expanded and overlapping areas of pain.  Treatment It is most important to maintain function of the affected body part by stretching out the trigger points, although it may first be necessary to relieve the severe pain this causes. This may be done using a vapor coolant spray, by compressing the part to cut down blood flow or by injecting a local anesthetic. Some believe that a ''dry'' injection (needling) or injecting saline (salt solution) is equally, or more, effective. If a number of trigger points are present in a confined area, individual injections may be replaced by a nerve block of the entire region. Regional sympathetic blockade may also be effective. Some patients gain relief using relaxation methods or biofeedback based on a recording of muscle activity
(electromyogram). These latter measures are intended to supplement but not replace the primary approach of injection and stretching (Hartrick, 1992). [177.83] Acupuncture Acupuncture to relieve pain (acupuncture analgesia) has been practiced in China for nearly 2,500 years. The practice is based on stimulating specific points on the body surface by inserting needles. Certain painful conditions, such as arthritis, headaches and dental pain, are amenable to acupuncture treatments. Recent uses for acupuncture include relief from the painful symptoms of AIDS. Now that infection is no longer a risk, acupuncture is becoming increasingly popular in western countries.9 [177.84] Heat Heat has been used to relieve pain at least since the time of the thermal baths in Rome, and still is in the Finnish sauna and many other settings. Locally applied heat relaxes muscles and dilates blood vessels. Increased circulation may remove painproducing substances from a site of injury or illness. Heat also could act by inhibiting neural pain signals. This method should be avoided unless there is normal cardiovascular and respiratory function (Yeh, et al., 1992). Age-old methods of local heating include the ubiquitous hot pack and heating pad, the use of liniments and plasters and the whirlpool. Two modern methods of generating more penetrating heat to reach deeper structures are diathermy and ultrasound.  Diathermy Shortwave diathermy is a form of deep heating that uses a highfrequency current to raise the temperature in the soft tissue just beneath the skin and the more superficial muscles. It can relieve pain even in deep-seated joints such as the hip. Two precautions: contact lenses should first be removed, and the method avoided if a metal implant is present as it may cause a burn. Another technique called microwave diathermy uses energy that is absorbed by tissues having a high water content (such as muscle tissue). Present units do not always operate efficiently, however, and ''hot spots'' are a risk (Wilensky, 1992). Diathermy causes the muscles to relax and relieves painful spasms. Arthritis is a frequent indication for its use, but actively inflamed tissues may be made worse. Reasons to avoid diathermy include vascular disease, recent radiotherapy or heavy bleeding and pregnancy. Also, patients who lack feeling in the target region or are unable to describe what they feel should not receive diathermy treatment (Melzack and Wall, 1988).  Ultrasound Today ultrasound energy is the most popular form of deep heating. High-frequency acoustic vibrations are converted to heat energy. Ultrasound energy tends to localize at the borders between bone and soft tissues, where injuries and lesions are very frequent. Bones, joints, muscle tendons, and large, deep-lying nerves are easily reached by ultrasound. Ultrasound energy also makes collagen, part of the soft tissue structure, more flexible and it induces muscle relaxation. This method is especially helpful in making the tissues surrounding joints less stiff (Vasudevan, 1992). The heart, malignant tumors, and areas of vascular insufficiency should not be exposed to ultrasound energy. Joint replacements also should be avoided, as the materials used absorb much ultrasound energy (Wilensky, 1992).
[177.85] Cold Applying cold (cryotherapy) is an easy-to-use method of suppressing inflammation, slowing nerve conduction, and countering muscle spasm. Ice is a popular counterirritant that very often is used in treating acute sports-related injuries (the acronym ICE means ice, compression, and elevation). Cold, always readily available, can relieve acute pain and limit edema formation (swelling) in the injured tissues. Methods of applying cold range from the simple ice pack to ''ice massage,'' cold baths, and a vapor coolant spray such as ethyl chloride. A rare patient will be hypersensitive to cold and of course should not be treated in this way. Raynaud's phenomenon, when the digital vessels constrict in the cold, calls for great caution (Vasudevan, 1992). [177.86] Massage Soft tissue massage is another easy way of relaxing muscles and promoting blood flow. A broad range of techniques are practiced by professionals, ranging from superficial, relaxing massage of much of the body to the application of deep pressure to a localized site of pain. Massage can show the physical therapist where trigger points or sites of muscle spasm are located. Hardened scar tissue can be softened by repeated massage. After a total-body massage, the relaxed patient will be able to engage in activities that formerly would have been too painful (Yeh, 1992). [177.87] Therapeutic Movement Pain limits motion and as such may seriously interfere not only with exercise but with the simplest of daily activities. Therapeutically guided movements, manipulation where indicated, and an individualized exercise regimen are key aspects of rehabilitation. Therapeutic movement is designed to restore muscle balance and correct limb and body posture, to extend the range of joint motion and through exercise to restore body functions and enhance the patient's general health.  Manipulation Just what manipulation of spinal and other structures consists of, and how safe it is, continue to be controversial. Manipulation as practiced by physiotherapists, osteopaths, physiatrists, or chiropractors,10 can undoubtedly help relieve low back or neck pain and chronic headaches. The better the lesion can be localized and defined, the likelier it is that manipulation will help. Some of the less common indications for manipulation are torticollis (also called wry neck, an abnormal posture of the head and neck), acute pain in the chest (which may be referred from the cervical spine) and rib pain. Many specific techniques exist for stretching, twisting and pulling on different parts in order to break up scar tissues and relax chronically contracted connective tissue and spastic muscles. The procedure sometimes is quite painful. The risk of serious side-effects will be reduced in the hands of a competent and experienced professional (Langley, 1994).  Mobilization Maximizing the range of joint motion in order to mobilize joints and improve limb motion involves taking a joint to its limit of passive motion, and then somewhat beyond it through manipulation. Caution is all important because excessive or too rapid mobilization may damage the ligaments attached to the joint. Both small oscillating movements and sharp jerks may be used. Once an increased
range of movement is achieved, appropriate exercises are begun (Yeh, et al., 1992).  Exercise In acute pain, exercise usually is limited to passive movements of the affected joints to prevent stiffening and ''locking up'' (contracture). More active exercises are indicated in patients with subacute pain (developing over days or weeks rather than abruptly), to maintain and restore function in the affected region. If pain is chronic, exercise is aimed at countering the effects of decreased activity, which may include muscle weakness, wasting (atrophy) of muscle tissue and contracted joints. In addition to its local effects, exercise, - especially aerobic activities such as cycling and swimming - can increase levels of endorphin in the brain and thereby lessen pain (Caillet, 1993). Generally the physical therapist will prescribe exercises in the same way that drug treatment is prescribed, and will supervise the patient's progress at frequent intervals. What exercises are done and the level of intensity are continually adjusted to the patient's progress. Often it is helpful for patients to exercise in a group setting.  Posture Faulty posture may contribute to many painful conditions resulting from injury, overuse and advancing age. Often poor postural habits, such as slumping, develop in childhood years. Spending long hours before a computer or wearing bifocal glasses may compromise good posture, and footwear also may be a factor. Emotions also are important; how we stand, sit and walk reflects how we feel. Examples of how poor posture can lead to musculoskeletal pain include too forward a head posture, which affects the upper spine, and shoulder pain caused by abnormal upper spinal posture (Caillet, 1993). [177.88] Vibrators and Percussion Use of a mechanical vibrator and the application of pressure to the tissues may help the patient relax or take attention away from pain. Percussion (the rhythmic application of ''beats'' of pressure) can have similar effects. Pain sometimes will increase before the patient feels relief (NCI, 1996). [177.89] Supporting Devices The use of a brace, collar, cane or crutches may be very helpful or even essential at times for limiting pain and allowing the patient to be as active as possible. A lumbar brace or support, by compressing the abdomen, increases pressure within the abdomen and lowers stress on the spine. The idea of using any support device is to restore correct posture and body mechanics and help gain muscle strength. The patient should stop using any support device as soon as possible so as not to become dependent on it. Restricting movement over the long term will weaken the muscles, restrict joint motion and produce abnormal postural changes. In patients with chronic pain it is especially important to periodically review and justify the use of a support device (Yeh, et al., 1992). FOOTNOTES: Footnote 7. See also ch. 12A for a complete discussion of acupuncture. Footnote 8. See also ch. 182.
Footnote 9. See also ch. 12A for a complete discussion of acupuncture. Footnote 10. See also ch. 12. P 177.90 BEHAVIOR MODIFICATION Chronic pain, with all its emotional, cognitive, behavioral, and psychosocial concomitants, may legitimately be viewed as a type of learned behavior. Just what pain means to, and for, a particular patient, and how much control the patient can exert over the pain experience, have a great deal to do with how pain is perceived. Accordingly, methods such as relaxation training, hypnosis, and ''re-learning'' (cognitive-behavioral approaches) have been widely used in conjunction with traditional pharmacological and physical methods of alleviating pain. Relaxation techniques lessen the state of arousal and make it possible, through suggestion and use of one's imagination, to gain some degree of control over chronic pain. Hypnosis operates in the area of suggestion. Its effectiveness, though acknowledged, still is largely unexplained, but hypnosis does provide a sense of peace and comfort and lessens pain over the short term. Finally, cognitive methods of pain management focus on the patient's expectations, beliefs and attitudes concerning pain. Patients can be taught specific methods for dealing with pain. The ''behavioral,'' or operant element of cognitive-behavioral therapy attempts to reinforce appropriate behaviors and to not reward pain behavior itself. [177.91] Relaxation The stress of suffering chronic pain, or of living under the threat that severe pain can occur at any time, can lead to a chronic state of muscle tension, high blood pressure, and excessive production of adrenaline. The latter, by increasing sympathetic neural activity, can worsen muscle tension or hasten the transmission of pain signals to the brain. Chronic sufferers may have ''forgotten'' how to relax, and must learn again how to do so in order to break this cycle. Focusing on one part of the body or on the breathing process can dispel the patient's constant preoccupation with pain. Relaxation often is used along with biofeedback methods. There is convincing evidence that relaxation helps relieve muscle contraction headaches, migraine, chronic back pain, pain arising form the temporomandibular joint (TMJ) of the jaw and myofascial pain syndrome anywhere in the body (Kelly and Lynch, 1992).  Progressive Relaxation PMR (progressive muscular relaxation) is the most widely used relaxation method for relieving chronic pain. It was popularized in the U.S. by Indian practitioners. Successive muscle groups (or a particular group such as the jaw muscles) are tensed for several seconds and then released, concentrating on how the muscles feel in these two states. Most often this sequence is applied to all major muscle groups, starting with the lower extremities. It may be combined with deep, rhythmical breathing, expiring when relaxing the muscles, and also with pleasant imagery (Gaupp, et al., 1994).  Benson Technique This method, too, is based on Eastern meditative practices. The patient sits quietly with the muscles relaxed, and focuses on breathing while repeating the word ''one'' (or ''om,'' or some other mantra) for 20 minutes. The more one practices, the more easily a fully relaxed state and sense of well-being are achieved (Melzack and Wall, 1988).
 Other Methods Autogenic training instructs the patient to concentrate on several states such as a steady heartbeat, a calm inner feeling, and warmth or heaviness of an extremity. In time the patient is able to rapidly assume a state of low arousal while remaining fully awake. Patients can learn to focus on some pleasing, personally meaningful event or experience, and make this part of whatever formal relaxation methods is being used. This tactic is called dissociative visualization (Gaupp, et al., 1994). Some patients are distracted from their pain when listening to favorite musical pieces (PHS, 1992). [177.92] Biofeedback Through the process called biofeedback, a patient can learn, to some degree, to influence body responses that ordinarily occur automatically, such as contraction and relaxation of the walls of blood vessels. Tension and migraine types of headache often respond to biofeedback training. Chronically tense neck muscles, fibromyositis and pain in the jaw or shoulder are other indications (Caillet, 1993). Examples of biofeedback are the recording of electrical muscle activity (the electromyogram) to lower muscle tension, thermal feedback from a finger to increase the temperature (through dilating the blood vessels) and recording the pulse of the temporal artery in the scalp to lower the pulse and counter distention of the vessel (a cause of headache). It is reported that biofeedback training can relieve phantom limb pain, angina (chest pain), painful menstruation, the severe pain episodes of sickle cell disease and pain from burn injury. There is growing interest in trying biofeedback in both children and the elderly (Gaupp, et al., 1994). No firm scientific basis for biofeedback training has been offered. Some or even most of its effect may result from the relaxation training which is often part of the process, on distracting patients from their pain and by providing some sense of control over pain. [177.93] Hypnosis Before the first anesthetics became available, hypnosis was used in an attempt to combat the pain of major surgery. Even today there are examples where hypnosis alone has sufficed, even for major abdominal surgery and open heart surgery. How deeply a person can be hypnotized (only about one-third can reach deep hypnosis, and 40 percent of all persons can be lightly hypnotized if at all) has much to do with whether significant pain relief is achieved. Hypnosis has relieved severe pain in burninjured children who require frequent dressing changes and cutting away of dead tissue. Cancer patients frequently are helped by hypnosis, even if some pain remains. Those who are able to achieve a deep trance may have dramatic relief of pain. Hypnosis has often proved useful in dental practice. The mechanisms underlying hypnotic effects remain poorly understood, but its ability to induce relaxation may be a key factor. How hypnotizability may relate to the placebo response is also an enigma. Patients under hypnosis tend to suppress outward signs of pain, and later they will report that they felt more comfortable while in the trance state (Orne, 1992). [177.94] Cognitive-Behavioral Approach
The cognitive-behavioral approach to relieving pain operates at two levels. Like any behavior, pain-related behavior can be altered through reward and punishment. Patients may be rewarded for appropriate behavior by receiving more attention or medication, and ''punished'' through actual adverse measures or simply by withholding reward. At the cognitive level, patients can learn new strategies that can change the way pain is perceived and experienced. Basic to this approach is to increase the patient's confidence in gaining some measure of control over pain responses. Contrary to what many believe, behavioral therapy does take into account the patient's past history, family and social relationships, educational level and work history. Relatives and friends are brought into the process whenever possible. The patient's interests and hobbies can provide valuable clues as to what will be the best reinforcers of desired behavior. The patient constantly receives feedback on whether and how much progress is being made. Cognitive therapy makes use of mental imagery and self-statements about the state of ones body as it changes over time. Patients can learn to distract themselves from their pain. Increased socialization may be very helpful. A given patient may benefit from reading, listening to music, exercising or watching television. The process by which a patient learns how to think about pain in a positive way and how to become less obsessed with the pain is called cognitive restructuring (Ott, 1992). Efforts should always be made to persuade patients that nearly all pain, no matter how severe, can be effectively managed. Some patients, especially those who are substance abusers or are clinically depressed, will benefit from short-term psychotherapy. Suicidal thoughts should never be ignored. All patients should be informed about support groups in their area. Often a religious counselor can help to define the patient's needs and offer spiritual support (NCI, 1996). P 177.100 PAIN CLINICS The various adjunctive measures to relieve pain as well as cognitive-behavioral treatment offer examples of the advantage of combining two or more treatments for the same patient. It is this impetus toward an interdisciplinary approach that inspired the establishment of pain clinics, or pain centers, where patients suffering chronic pain can participate in an individualized management program. Any and all modalities are offered, but management often attempts to minimize drug use, modify pain-related behavior, maximize function and promote psychosocial rehabilitation. Strong emphasis is placed on enabling the patient to return to work, even though the suggested job may differ from past employment. The overall goal is not to totally eliminate pain, but to make patients better able to cope with it and more confident in living a normal lifestyle (Aronoff and McAlary, 1992). Whatever specific measures are offered patients at pain centers, certain attributes are constantly emphasized. They include: comprehensive patient education by interested staff; stress management skills; the ability to communicate assertively;
how to interact positively with others; and maintenance of high self-esteem. Follow-up planning is a key aspect of management. Maintaining positive behavioral changes over the long term calls for careful planning. Any quality program will develop meaningful ways of monitoring its effectiveness on a regular basis. Part of this process is to ascertain how satisfied patients are with their management and outcome (Chapman, 1994). P 177.110 HOME CARE Economic considerations have prompted increasing interest in home health care in general. Pain management is one of the latest forms of home care. Home care agencies provide for laboratory and pharmacy services, financial arrangements, and whatever social, dietary, or other services may be needed in a given case. For many, perhaps most, seriously ill patients, home is the optimal site at which to be cared for. It must be clear that home treatment will be more cost- effective than a prolonged stay at a hospital or other institution. Infusion of medication is the cornerstone of home pain management. Catheters placed either beneath the skin or within a body cavity are used to constantly infuse analgesic drugs. Infection is a major concern, but intraspinal infusion, a common approach, carries a relatively low risk of infection. A leaking or broken catheter and bleeding are the other major complications. Good clinical results are reported in patients given combinations of drugs by infusion for prolonged periods at home. Hopefully the future will bring to home pain management smaller, more efficient, and safer delivery systems, easier means of monitoring patients and analgesic drugs that are safer and cause fewer side-effects. It should not be long before the patient's condition can be automatically monitored and transmitted by radiofrequency communication (Leak, 1992). P 177.120 PATIENT EDUCATION Today's patients being treated for chronic pain must understand the needed procedures, what to expect from them both positively and in terms of side-effects and what they can do to optimize their status at any given time. In the area of chronic pain, even more than with other conditions, it is vital that the patient be a knowledgeable and active part of the treatment team. Patients should be encouraged to ask questions, not only of their physicians but of all practitioners, such as nurses and physical therapists, who contribute to their care. A biomechanical explanation of what has gone wrong and how it may be approached therapeutically is often a good starting point. A patient with chronic low back pain, for instance, will learn the importance of proper posture, how to perform various activities with the least stress on the lower spine and how to maintain strength elsewhere in the body. The result will be a patient who enjoys physical activities more confidently and with less fear of reinjury or worsening pain (Yeh, et al., 1992).