Current Diagnosis & Treatment of Pain, 1st Edition

1. The Current Issues in Pain Management

John D. Loeser MD

History

The present status of pain control is understandable only by looking backward at the developments of the past 45 years. In the 1960s and 1970s, John J. Bonica, MD, called attention to the inadequate treatment of pain as well as the absence of scientific information about the physiologic and psychological mechanisms of pain. Almost single-handedly, Bonica stimulated interest in physicians and scientists, raised funds from the National Institutes of Health and pharmaceutical companies, and attracted a motivated group of followers who carried his message all over the world. Before the efforts of Bonica, pain was always the by-product of a disease, and physicians who treated the diseases were expected to manage their patients' pains. Unfortunately, this often did not happen. Patients suffered needlessly, scientists did not recognize the need for basic and clinical studies on pain, and no one was willing to fund the necessary research.

By 1980, Bonica had changed the scene dramatically. The International Association for the Study of Pain and many of its national chapters had been founded, journals were being published, granting agencies recognized the need for funding of pain research, and clinical care was improving. Training programs and educational activities at all levels and in all the health professions expanded dramatically. Professional organizations were founded to provide a forum as well as educational activities about pain.

The treatment of pain has always been part of the physician's duties; only in the past 25 years have we seen the development of specialists in this new area of medicine. New concepts and new technologies have led to the development of the field of pain medicine.

In spite of major improvements in the understanding of the anatomy, physiology, and psychology of pain, and the application of many new treatments, chronic pain continues to be undertreated. Patients' complaints of pain remain second only to the common cold as a reason to see a primary care practitioner in the United States. Treatment of postoperative pain and cancer pain has improved significantly as has the management of pediatric and geriatric pain problems.

Key Developments

The improvements in pain management have been based primarily upon new concepts and paradigm shifts. Technologic advances in drugs, drug delivery systems, stimulation systems, and strategies of psychological interventions have all been significant.

Paradigm Shifts

A critical leap forward was the Melzack-Wall gate hypothesis, published in Science in 1965. This hypothesis focused attention upon modulation of afferent information, both at the dorsal horn and at suprasegmental levels. Line labeling was wrong; the nervous system was capable of controlling the upstream flow of information to the brain by modulating afferent activity through downstream circuits. This theory led directly to the attempt to reduce pain by non-noxious afferent input, such as transcutaneous electrical nerve stimulation and spinal cord stimulation with implanted electrical devices. It also paved the way for research on peripheral nociceptive mechanisms and dorsal horn synaptic mechanisms that could be influenced by medications. Drugs were studied, developed, and marketed that could alter the downstream modulation of dorsal horn information processing. The gate hypothesis also led to the realization that pain behaviors were influenced by affective and environmental events and that psychological strategies could be used to help reduce the impact of noxious stimulation on a person's cognitive and affective processes. This key theory led to the realization that a biopsychosocial approach to pain was far more effective than the traditional biomedical concept of pain being a genetically determined response of the brain to a noxious event.

A second paradigm shift was the recognition that tissue damage was not synonymous with pain and not directly linked to suffering or to pain behaviors. In 1982,

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the terms “nociception,” “pain,” “suffering,” and “pain behavior” were defined and helped channel thinking, research, and patient care into different components that could be addressed by specific pharmacologic, psychological, or surgical techniques. There are only loose linkages between tissue damage, pain, suffering, pain behaviors, and disability. Suffering and the behaviors it can generate are not always due to tissue damage (nociception) or to pain. Pain behaviors can be perpetuated by environmental factors and anticipated consequences-influences that cannot be evaluated.

The importance of listening to the patient's story and placing it within the context of his or her thoughts, beliefs, and culture, cannot be overemphasized; without listening to the patient, the symptom presentation and the responses (or lack thereof) to treatment cannot be understood. Just listening to the patient's narrative can have a therapeutic effect.

In some ways, the biggest conceptual change was promulgated by Wilbert Fordyce at the University of Washington; he demonstrated that the environment strongly influenced pain behaviors, and factors outside the patient were often responsible for the perpetuation of chronic pain behaviors. In addition, how people think and what they fear and anticipate are also strong determinants of suffering and pain behavior. Good pain management programs are now built upon a cognitive-behavioral approach and incorporate physical, pharmacologic, and psychological treatment strategies. Indeed, the best outcomes data that we have for the treatment of chronic pain comes from such programs. No isolated surgical, pharmacologic, physical, or psychological treatment has been shown to be as good as multidisciplinary pain management for refractory chronic pain. Unfortunately, this form of treatment is thought to be expensive and is poorly funded by most insurance programs.

Role of Opioids

Another conceptual change relates to the use of opioids in the treatment of both acute and chronic pain. Fear of opioids discouraged the rational use of these drugs except in the setting of trauma or postsurgical pain. Eventually, the lessons learned from the management of cancer pain reduced some of the fear of opioids. By the 1990s, much more aggressive use of opioids in the treatment of cancer pain was becoming standard. Although opioids are used more frequently, efficacy data for opioid therapy in noncancer pain conditions are scarce. Other forms of treatment for chronic pain may be more effective than opioids. Finally, the discovery of opiate receptors in the dorsal horn of the spinal cord led to the spinal administration of opioids. For properly selected patients, this has offered a dramatic improvement in pain relief.

Concepts of Pain

Physician-Patient Communication

The individual and his society can only understand the relationships between tissue damage, a person's report of pain, and the behaviors manifested by the patient if there is a meaningful conceptualization of the phenomena of pain and shared definitions of the terms that are used in a discussion of pain. Discussions of pain and suffering often fail because of disagreement about the meanings of the words used. Understanding their pain and suffering requires listening to the patients' stories.

Mechanisms of Pain & Suffering

The aspect of pain and suffering has long been overlooked by pain researchers. Reflex responses to noxious stimuli can occur without consciousness, but the presence of a nociceptive reflex is not a proxy for pain. A patient with a spinal cord transection due to injury may feel no pain when his toe is squeezed, but this noxious stimulus may generate a set of somatic and autonomic reflex responses. The development of brain imaging by positron emission tomography (PET) or functional magnetic resonance imaging (fMRI) has opened new windows for understanding the mechanisms by which pain, suffering, and their narratives are generated in the human brain. To make full use of this technology, we need concepts and terms that are reflective of the events within the nervous system that lead to the phenomena we wish to investigate.

Components of Pain

Four components comprise the complex phenomenon of pain: nociception, pain, suffering, and pain behavior (Figure 1-1). These components can help generate useful models that are compatible with what we are learning from brain imaging and psychological studies. This model allows us to construct a scientific vocabulary that will aid in research and clinical management.

  1. Nociception

Nociception is the detection of tissue damage by specialized transducers attached to the A delta and C fibers that transmit signals to the dorsal horn. Peripheral transducers may be biased by inflammatory and neural changes in their immediate environments and thereby alter their response characteristics. The nociceptive transducers, in their basal state, turn on at a level of mechanical, thermal, or chemical energy that is just sufficient to damage cells. Nociception can be blocked by local or regional anesthesia, usually accomplished by sodium channel blockers since they prevent axonal depolarization. Nociception can also be blocked by downstream modulation from

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the brain to the dorsal horn, as originally proposed in the Melzack-Wall gate hypothesis, for example, by hypnosis or distraction. Modulation is a feature of the human brain and is just as worthy of study as are afferent projection systems.

 

Figure 1-1. Nociception, pain, suffering and pain behavior are the four components that are necessary and sufficient to describe the phenomenon of pain. They have been drawn in an onion-skin pattern to emphasize that all except pain behavior are personal, private, internal events that cannot be measured objectively. (Reproduced, with permission, from Loeser JD. Concepts of Pain. In: Stanton-Hicks M, Boas RA, editors. Chronic Low Back Pain. New York: Raven Press, 1982:145-148.)

  1. Pain

The response to nociception is properly labeled pain. Pain is generated in the spinal cord and brain by nociceptive input (in the intact animal). Injuries to the peripheral nervous system, spinal cord, or brain can lead to the report of pain even in the absence of a noxious stimulus; for example, patients who have had a limb amputated may report pain in the missing limb (phantom limb pain). Some well-known clinical examples of pain without nociception include the following:

  1. Thalamic syndrome.
  2. Tic douloureux.
  3. Phantom limb pain.
  4. Complex regional pain syndrome.
  5. Atypical facial pain.
  6. Postparaplegic pain.
  7. Postherpetic neuralgia.
  8. Nerve root avulsion pain.
  9. Arachnoiditis.
  10. Postthoracotomy pain.
  11. Suffering

Suffering is a negative affective response generated in the brain by pain, fear, anxiety, stress, loss of loved objects, and other psychological states. What we do not know is whether this negative affective response to pain originates within the brain when information saying “pain” is received, or whether nociceptive information reaching the dorsal horn of the spinal cord leads to the activation of circuits leading to the production of both pain and suffering at the spinal and brainstem levels. That is, is suffering added onto pain in the brain or does it have an anatomic underpinning that starts in specific spinal projection systems? Very little research has been done on suffering, either from the physiologic perspective or from the behavioral viewpoint, although recent functional imaging studies have elucidated brain regions that play a role in suffering.

Suffering should be important to health care providers. Along with pain, it is what drives patients to seek medical care. However, to understand suffering, clinicians must listen to the patient, and listening takes time. Because of the demands on physicians' time, few patients have adequate access to their physicians to allow for an understanding of their suffering.

  1. Pain Behaviors

Suffering usually leads to pain behaviors. Grimacing, moaning, limping, lying down, continuous seeking of medical care, and failing to work are common pain behaviors that often occur when someone is suffering. All pain behaviors are real. The proper question for the health care provider is not the validity of the patient's complaints, but which of the four components is contributing to the complaint and what can be done to alleviate the symptoms.

Pain behaviors are always influenced by environmental prequels and consequences, either actual or anticipated. Pain behaviors that are chronic and expressed over time reveal with special clarity the influence of the environment: behavior, in this sense, is the result of learning. The role of anticipated consequences is nicely demonstrated in the 1993 work of Waddell and colleagues, who showed that fears about back injury were a major determinant of disability status and health care consumption.

Only pain behaviors, the things a person says and does, or avoids doing, can be measured. They are truly objective-in the sense of constituting recordable events-but they do not quantify the events within the patient. They have qualities that can be described: onset, duration, intensity, frequency, periodicity, type. Pain behaviors can be measured also in terms of the amount of

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disability they produce, the consumption of health care, or their impact upon quality of life.

How societies deal with suffering differs widely at different points in history. To some degree this difference is due to variations in the resources available to a society, but more is involved than resources. A society must be able to define and identify suffering before it can effectively respond.

Chapman CR et al. A passion of the soul: an introduction to pain for consciousness researchers. Conscious Cogn. 1999;8:391.

Loeser JD et al. A taxonomy of pain. Pain. 1975;1:81.

Melzack R et al. Pain mechanisms: a new theory. Science. 1965;150:971.

Waddell G et al. A Fear-Avoidance Beliefs Questionnaire (FABQ) and the role of fear-avoidance beliefs in chronic low back pain and disability. Pain.1993;52:157.

Types of Pain

There are four types of pain that are important to distinguish in the clinical setting: transient pain, acute pain, chronic pain due to cancer, and chronic pain due to non-malignant diseases.

There is no evidence that the neurophysiologic mechanisms underlying these four types of pain are different or that different neural circuits are involved, but in clinical medicine, the principles of management of each type are so different that it is important to discuss them independently. The future will tell us if these diverse types of pain have different neural substrates.

Transient Pain

Transient pain is elicited by the activation of nociceptors in the absence of tissue damage, such as with a needle stick. It occurs frequently in everyday life and is rarely a reason to seek health care. Relevant only to procedural pain, this is not a major issue in clinical medicine, although it is important in pediatric health care and in the performance of certain procedures such as venipuncture, lumbar puncture, and bone marrow aspiration. It has, however, been the subject of most experimental pain paradigms in humans and animals until the past 20 years. The failure to look at animal models of pain associated with tissue damage was one of the reasons why so little useful information was gleaned from such studies.

Acute Pain

Acute pain is elicited by injury to the body and the activation of nociceptive transducers at the site of damage. The local injury alters the response characteristics of the regional nociceptors, their central connections, and the autonomic nervous system in the region. Nociceptor activity is processed in the dorsal horn and leads to the report of pain when upstream projection systems reach the brain. Healing of damaged tissue occurs and the restoration of normal nociceptor function is even more rapid than the entire healing process. Acute pain is a common medical problem, seen after surgery and trauma. The role of the health care provider is to treat the injury (eg, immobilization, suture of the skin) and to provide analgesia until the nociceptor function returns to baseline. After the acute injury has healed, the pain abates and the person can resume normal activities.

Chronic Pain due to Cancer

Chronic pain due to cancer is almost always associated with continuing tissue damage due to the disease process or the treatments (ie, surgery, radiation, chemotherapy). Although there is always a role for environmental factors and affective disturbances in the genesis of pain behaviors, these are not usually the predominant etiologic factors in patients with cancer pain. Furthermore, many patients with severe pain associated with cancer are nearing the end of their lives and palliative therapies are required. Issues such as social stigma of using opioids, work and functional status, and health care consumption are not likely to be important in the overall case management. Hence, the typical strategy for cancer pain management is to get the patient as comfortable as possible using opioids and other medications, surgery, and physical measures.

Chronic Pain due to Nonmalignant Diseases

Chronic pain due to nonmalignant diseases is an entirely different management problem. Typically, the pain complaints have been triggered by injury or disease in the past. Healing from such an injury should have occurred long ago. The pain is likely being perpetuated by factors other than those that were present at the time of the injury. The body is unable to heal because of a nerve injury, the loss of a body part, or changes in the central nervous system that persist after healing. Reorganization of spinal and brain modulatory systems may have occurred after the original traumatic events in the periphery, or the injury was directly to the nervous system and there is disruption of normal pathways; compensatory mechanisms may be perpetuating the pain. Because the pain is present over time, stress, affective, and environmental factors are likely to play a large role. When dealing with chronic pain, clinicians should not just focus upon the patient's symptoms but must also evaluate the roles of affective and environmental factors. Treatment must

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incorporate not only symptom relief but also restoration of well behaviors, including work. This means that chronic pain is not well managed by the utilization of Cartesian or Aristotelian concepts of the separation of mind and body. Instead, it requires a biopsychosocial model. Since the altered nervous system may not be amenable to standard pain-relieving therapies, control of pain through the activation of modulatory circuits may be the best available treatment. Hence, psychological strategies built upon cognitive and behavioral principles are useful.

Chronic pain, especially low back pain, is common, affecting 80% of persons at some point in their life. Most episodes of back pain are self-limiting, regardless of the health care delivered. The introduction of Western health care to Oman led to a surge of disability ascribed to low back pain without a change in the prevalence of pain. Health care and its many meanings and cultural links altered the way people thought about their symptoms and what actions they took because of their complaints.

Waddell G. 1987 Volvo award in clinical sciences. A new clinical model for the treatment of low-back pain. Spine. 1987;12:632.

Patient Issues

Issues that patients with acute and chronic pain face include the following:

  1. There is wide variability in the resources allocated to pain management.
  2. There are many subspecialties among pain specialists, making it difficult for patients to find the physician who might be most helpful.
  3. There are very few commonly agreed upon treatment algorithms and almost no evidence-based treatment plans.

Acute Pain

Inadequate management of acute pain is still common in the United States due to the lack of resources. Efforts by the community of pain specialists have succeeded in making pain “the fifth vital sign.” The Joint Commission on Accreditation of Hospitals has mandated that hospitals assess and treat pain in every inpatient and outpatient.

Nursing has played a leadership role in this change in procedures and policies. However, postoperative and posttrauma pain is very variably treated. Techniques of drug administration beyond oral medications or the intramuscular injection are not readily available in smaller hospitals. To some degree this is due to the lack of funding for pain management services. Furthermore, not all institutions have the equipment or staff to offer patient-controlled analgesia, intravenous infusions, or neuraxial opioids. Advanced pain management techniques are expensive and potentially hazardous, so there are often arguments against their use. Nurses need extensive training and physicians need very detailed education to provide the full gamut of acute pain management services. There remains a tendency to say “It is only pain” and “just wait until nature solves the problem in a few days.” In addition, often there is a belief that pain is somehow good for the patient when, in fact, there are plenty of data to show that pain delays recovery from surgery and raises the likelihood of many complications.

Acute pain management can be improved without the development of new drugs or techniques of administration, although both of these will happen and lead to better patient care in selected cases. In the interim, physicians, nurses, and pharmacists need to be better educated about the available options. We must work to change the reimbursement systems prevalent in hospitals so that the provision of good pain management services is financially rewarded. Some HMOs have solved this problem by determining that they will have trained physicians and nurses on staff to provide the best possible pain management services. Other prepaid health care plans virtually exclude pain management services for their members. Hospitals as well as physicians need to be rewarded for providing optimal treatment for acute pain. Of course, we can anticipate that there will be new, useful drugs and treatments. However, we cannot wait for these to appear and must do a better job with what is available.

Chronic Pain due to Cancer

Tremendous progress has been made in the past 25 years in the management of cancer pain. Some interventional techniques, such as regional anesthesia and implantation of intrathecal catheters, have advanced the care of patients with chronic pain due to cancer. However, the progress in cancer pain management is mainly due to the more aggressive use of opioids and adjunctive medications.

Social stigmata are fewer, and the federal and state agencies do not scrutinize prescriptions for cancer pain nearly as much as they do for patients with chronic pain of nonmalignant origin. The treatment ladder for cancer pain established by the World Health Organization (WHO) has been widely accepted throughout the world and has set a reasonable initial approach into every physician's repertoire. Some patients with cancer pain require immediate implementation of strong opioids and rigid interpretation of the WHO ladder can be an impediment to their adequate treatment. It is commonly accepted that patients with cancer should not have to suffer with pain and that they are entitled to every possible effort to reduce their pain, no matter what the dose of medication

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or the magnitude of the intervention to control pain. This is not to say that there is not a large amount of variability in the quality of pain relief services that are offered to cancer patients. There have been successful lawsuits claiming inadequate attempts at pain relief by physicians and nursing homes, and certainly there will be more litigation on this issue. Clearly, both better tools for the treatment of pain due to cancer and more universal application of the medications and delivery strategies than we have available today are needed. Moreover, the desires of patients to obtain pain relief seem to be congruent with the interests of health care providers to make this possible. This is clearly not the case in patients with chronic pain due to nonmalignant disease.

Chronic Pain due to Nonmalignant Disease

Patients with chronic pain due to nonmalignant diseases often do not get adequate treatment. There are many factors that contribute to this unhappy state of affairs. First, accurate diagnosis of the causes of the pain may not be possible. Second, adequate treatments for the pain, even when the cause is thought to be known, may not be available. Third, we do not understand the mechanisms underlying chronic pain, and therefore, all of the treatments are empiric and lack a rational basis. Fourth, apparently identical injuries do not predictably lead to pain, so the link between tissue damage and the complaint of pain is not strong. This suggests, of course, that in addition to the tissue damage that might start a chronic pain process, there are changes in the nervous system in response to injury that long outlast the inciting cause of pain. Also, environmental and affective factors may contribute to chronic pain and may not be discernable by examination of the patient or the imaging studies.

Treatment of Nonmalignant Pain

The treatments for chronic pain due to a non-malignant disease are often inadequate. Anticonvulsants, antidepressants, antiarrhythmics, nonsteroidal anti-inflammatory drugs, and opioids sometimes work but often do not. If the data on efficacy of opioids in the treatment of this type of chronic pain is carefully examined, a 30% reduction in Visual Analogue Scale pain levels seems to be standard. Now, reducing a pain from a 9 to a 6 is certainly helpful, but a level 6 pain is by no means a cure of the problem of pain.

Determining peripheral mechanisms of pain has become a focus of drug companies, so that they can develop drugs aimed at treating all pain syndromes that have a similar mechanism. Thus far, we have not succeeded in identifying mechanisms underlying any pain syndrome. Hypotheses based upon animal experimentation are plentiful but unproven in humans. The role of genetic differences in response to injury has been studied in rodents, but human studies are few and far between. It may be that specific genes determine how a person's spinal cord responds to an injury or it may be that genes determine the behaviors produced in the brain in response to an injury. Hopefully, fMRI and PET scanning will provide insights into how the brain functions in response to injury and what parts of the brain are involved in generating a behavioral and affective response.

Finally, the roles of affect and environment in the generation and perpetuation of chronic pain are largely unexplored. Clearly, environmental factors play a role; however, how and why they impinge on those parts of the brain that generate pain behaviors is not understood. Again, genetic factors may be in play. Past experiences and anticipated consequences are also relevant factors in many patients with chronic pain. For many patients, these factors may be more important than the precipitating injury, but health care providers often ignore them. Curing chronic pain is a very rare event.

Variations in the Treatment of Pain

Patients with chronic pain are subjected to wide variations in the type of care they receive. There is no commonly agreed upon diagnostic or therapeutic algorithm for most chronic pain states. In addition to all the alternative care options, within allopathic medicine the treatment that the patient receives is more a reflection of the type of physician that is consulted than the patient's diagnosis. Csordas and Clark illustrated this problem by studying the 25 available pain treatment facilities in a single urban community in the United States. They reported that 27 different treatment modalities were used, with no two treatment facilities offering identical programs. Patient selection criteria, intensity and duration of treatment, the components of treatment, costs, and follow-up plans all differed. In addition, what treatment options exist for any particular patient are determined not only by the physician's wishes but also by the type of health insurance program that the patient is enrolled within; benefits for pain management vary widely and the payers often participate too much in the treatment decision-making process.

Measuring Outcomes

Determining outcomes for pain management and ascertaining the effects of treatment upon those outcomes is not the least of the problems. Whoever gets to determine the relevant outcomes will strongly influence what treatments are offered to patients with chronic pain. Almost everyone agrees that one aspect of outcome is the patient's self-rating of his or her pain, often obtained with a Visual Analogue Scale, although other validated measures

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exist. Most experts agree that this is only a portion of the information needed to determine the effects of a treatment. A patient's report of pain is certainly an important communication, but the meaning of this behavior needs to be determined by acquiring more information. Such things as functional status, health care consumption, and work status are also highly relevant in the assessment of the effects of treatment.

Functional status may be ascertained on validated questionnaires, such as the Oswestry, SF-36, or other objective measures of the patient's behavior. Health care consumption can include such markers as visits to the emergency department, office visits, hospitalizations, and medication consumption. Working, either in the home or at outside employment, is a helpful measure of outcome. Finally, there are numerous quality-of-life measures that can be used to assess overall well-being.

Once criteria for the measurement of outcome has been established, it is possible to determine costs of achieving that outcome and develop comparative measures of cost-effectiveness for different treatment strategies. Such measures do not take into account the risks to the patient nor do they consider patient preference as a determinant of outcome. This has been shown in several studies tomake an important contribution to a successful outcome.

In the United States, far more resources are devoted to the transplantation of hearts than to management of chronic pain, even though the economic and social burden of chronic pain dwarfs that of end-stage heart disease.

New Developments

There are many new drugs that have been developed that are used for pain management. Ironically, few, if any, were actually developed as pain-relieving substances; most have been marketed initially as anticonvulsants or antidepressants, blood pressure control agents, or anti-spasticity drugs. One area that has seen great activity is the treatment of neuropathic pain. Opioids are often not as useful for this type of pain; anticonvulsants have long been known to help some patients. New anticonvulsants, such as gabapentin, are now used more often to treat pain than they are to treat epilepsy, which was its original indication. Similar sodium channel blockers are being evaluated as pain relieving drugs. There has been a surge of interest in neuropathic pains in the past decade. It has at last become widely recognized that neuropathic pain often does not respond to standard analgesics, opioids, or other medications. The pharmaceutical industry has targeted the development of neuropathic pain treatment. Systemic and topical agents that are now available have significantly increased the treatment options and improved overall treatment results.

Modern brain imaging techniques, such as PET scanning and fMRI scanning, have improved the understanding of brain function. This is likely to lead to new drug treatments as well as an explosion of electrical stimulation techniques to treat pain. Motor cortex stimulation for neuropathic pain is likely to be the next major step forward, but associated conditions (such as depression, obsessive-compulsive disorder, and panic disorder) may soon have treatment opportunities through implanted stimulation or drug delivery systems. Functional imaging of the brain is a new area of endeavor, and it is not clear how far this area will develop into new treatment modalities.

Intrathecal drug delivery systems have been used clinically for the past 15 years to treat both spasticity and pain. The technology is reasonably effective, but better hardware is on the horizon. In addition, there is the opportunity to develop an entirely new set of pharmaco-logic agents that will work at the dorsal horn level to alter spinal cord function. Other methods of delivering drugs that do not require a pump or fluid delivery system are also under development.

New medications that target specific molecular complexes or membrane channels are being studied. Coupling a toxic agent to a protein that is incorporated at specific sites in the cell membrane or cytoplasm offers a new way of selectively damaging specific axons or synapses and sparing other classes of cells. Making use of axon transport systems permits the delivery of a drug to sites remote from the injection point in a highly selective fashion. Similarly, targeting specific genes within neural and glial cells to alter their function can become a new therapeutic modality.

Ablative neurosurgical procedures have become much less common in pain management, in part because of the development of aggressive oral and intrathecal opioid therapy, but also because long-term results were found to be not as good as the early proponents had claimed. Widespread use of opioid therapy seems to be meeting a similar fate; opioid use is becoming more limited. Behavioral and cognitive techniques are not being usedas much as the evidence suggests they should. Funding issues may be at play in this area as well as an unawareness of the potential benefits of biobehavioral medicine. Many of the alternative health care pain treatment strategies are going to fall by the wayside as outcomes-based medicine studies the efficacy for such modalities as chiropractic manipulation, acupuncture, dietary regimens, food supplements, and magnets.

There are some patients who respond well to opioids with reduced pain behaviors and increased functional abilities. Then, there are others who manifest rapid tolerance and never get pain relief. Other patients have intractable side effects that cannot be adequately controlled. Yet, most patients have both some benefits and

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some problems with opioids. No one yet knows how to predict who will have a good response and who will not. The percentage of good results with opioid therapy is not known.

Csordas TJ et al. Ends of the line: diversity among chronic pain centers. Soc Sci Med. 1992;34:383.

Kalauokalani D et al. Lessons from a trial of acupuncture and massage for low back pain: patient expectations and treatment effects. Spine. 2001;26:1418.

Mondloch MV et al. Does how you do depend on how you think you'll do? A systematic review of the evidence for a relation between patients' recovery expectations and health outcomes. CMAJ. 2001;165:174.

Societal Issues

Costs of Chronic Pain

The treatment of patients with chronic pain due to non-malignant diseases is an issue for society as well as the individual patient. Health care resources are finite and what is consumed in one area is not available in another. Furthermore, the costs of the social support systems provided to those who are unable to work because of pain are three to four times the costs of the health care they consume. Not only are there direct costs of wage replacement systems and the administration of such programs, but there are indirect costs such as loss of taxes on income and expenditures, loss of skilled workers necessitating training of new workers, and the huge psychological and economic burden placed on those who do not work and their families.

The magnitude of the chronic pain problem in industrialized societies is enormous. Population surveys, utilization of resources such as hospitalization data, operations performed, outpatient visits, prescriptions, over-the-counter medications, physical treatments all indicate the widespread prevalence of chronic pain. We have very little data on the use and costs of complementary and alternative medicine, but we do know that they are heavily used. By far, the most important type of chronic pain from the viewpoint of the patient, health care providers, and society is low back pain. The point prevalence for low back pain in the United States and European countries ranges from 14 to 42%, and the lifetime prevalence ranges from 51 to 81%. Surprisingly, the 5% of back pain patients who do not respond to therapy are responsible for 90% of all costs for back pain. We know that the correlations between pain, suffering, pain behaviors, and work disability are generally low and explain less than 25% of the variance.

In addition, the disability ascribed to chronic pain has become a major cost for developed societies. The total costs are thought to be $100 billion in the United States and $9 billion in the United Kingdom. Estimates suggest that 1 to 5% of the gross domestic product is expended on low back pain in Western societies. Disability costs far exceed health care costs. One way of looking at the costs of chronic pain is from survey data such as that published by Stewart et al. In the American workforce, 53% of workers report having had a pain problem in the past two weeks, 13% have lost productive time averaging 4.6 hours per week. This loss of productive time is estimated to cost $61 billion per year and accounts for about 25% of all costs related to pain in the workplace. Chronic pain costs American businesses $240 billion each year, and these costs are rapidly increasing.

Headache is the most common form of pain recalled in most surveys. Over 75% of the adult population report having headaches, and 5% report headaches more than 100 days per year. Although headaches are responsible for many sickness days and much absenteeism, they are not a major cause of health care costs and wage replacement. Other types of pain are also relatively common: menstrual pains, abdominal pain, extremity pain, neck pain, arthritis pain, and dental pain. Added together, these do not equal the impact of low back pain on health care or disability systems.

Disability Ascribed to Chronic Pain

Disability ascribed to chronic pain is a major concern for society because over 75% of the costs are related to the inability to work and not the symptom of pain. We know that addressing only the symptom of pain behavior fails to restore most patients with chronic pain to gainful employment. This is a major problem for medicine in the United States, since physicians are mandated to determine on the basis of a history, physical examination, and diagnostic studies whether or not a patient is capable of employment. There are serious ethical issues hidden in this mandate because the doctor-patient relationship is violated by providing information about the patient to a governmental agency or insurance company without the patient's consent or with the coercion that the insurance company will only pay for care if it has full access to the patient's medical records.

Rating Disability

Determining the amount of disability that is ascribed to a complaint of pain is a problem. The American Medical Association Guide for the Assessment of Impairment, now in its fifth edition, is the commonly used system; the idea behind this guide is that loss of a body part or the function of this part can be given a percentage of total disability. However, there has never been any validation of the methods promulgated in this volume, and pain is

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largely ignored by those rating disability. Yet, disability ascribed to pain is the major cause of disability in the federal programs in the United States.

Managing Disability

Yet another issue is the management of disability ascribed to pain. The systems that are in place in the United States today seem to have been designed to use behavioral principles to increase and prolong disability, rather than the reverse as most would desire. Being enmeshed in a compensation system is a type of comorbidity that adversely affects outcomes for any condition, including pain. Financial incentives, such as a high wage-replacement ratio, tend to perpetuate disability. The systems tend to have dehumanizing influence that contributes to the failures of the health care system to rehabilitate vast numbers of patients.

Cultural Differences & Aging Populations

As our population ages, chronic diseases including chronic pain associated with arthritis and neuropathy become more prevalent. More health care resources will be required to adequately manage the complaints of the elderly. Outcomes-based diagnostic and therapeutic algorithms are essential. Preventive programs would, of course be most effective, but insurance companies are generally not interested in such because the average beneficiary changes insurance carriers every three years. We cannot wait for such data to be produced, for patients want their symptoms alleviated now, with whatever resources may be available and with whatever treatment strategies their provider has to offer.

Quo Vadis?

Despite the widespread use of opiates for chronic, non-malignant pain, there are no data on long-term efficacy or complications. Furthermore, there is no head-to-head testing of one type of treatment versus another. Prodigious numbers of nerve blocks and corticosteroid injections are performed for back pain with little, if any, evidence for long-term outcomes. The cost for these injection therapies was over $250 million to Medicare, which funds a minority of health care costs in the United States. Major increases in the rate of surgery for low back pain have not resulted in improved function or pain relief in most patients. Chiropractic and naturopathic practitioners are treating more and more pain sufferers but results are unclear. The role of nonspecific treatment factors in clinical outcomes needs much more exploration.

Vast sums are spent by individuals and society in the treatment of chronic pain and support of those who do not work because of pain. Patients suffer without adequate treatments and now 15% of the gross national product goes to health care in the United States. The costs, both to the patient and society are large. We need a new conceptualization of the meaning of the complaint of pain and its management.

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