Fw: Management of chronic pain

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Subject: Management of chronic pain

Articles

Management of chronic pain

A Ashburn, S Staats

Posted April 21, 2001

Department of Anesthesiology, University of Utah Health Sciences Center, Salt Lake City, UT 84132, USA (Prof A Ashburn MD); and Department of Anesthesiology, Pain Management Center, s Hopkins University, Baltimore, MD (Prof S Staats MD)

Correspondence to: Prof A Ashburn

Types of chronic pain Effect of chronic pain Management of chronic pain Conclusion References

Chronic pain is a common condition for which patients seek care from various health-care providers. This type of pain causes much suffering and disability and is frequently mistreated or undertreated. Patients who present for evaluation for chronic pain should undergo a careful assessment before therapy. Patients with chronic pain commonly experience depression, sleep disturbance, fatigue, and decreased overall physical and mental functioning. They frequently require an interdisciplinary model of care to allow care givers to address the multiple components of the patient's pain experience. After a careful evaluation, therapy may include medication, nerve blocks, active physical therapy, behavioural interventions, and assistance with vocational evaluation and training. Less frequently therapy may include placement of implantable devices to alter the pain experience. These patients suffer from a chronic condition and often require long-term care, with frequent reassessment and adjustment of therapy. Although cure is possible, it is also infrequent. Therefore, therapy is provided with the aim of decreasing pain and suffering while improving physical and mental functioning.

Chronic pain affects hundreds of millions of people worldwide and alters their physical and emotional functioning, decreases their quality of life, and impairs their ability to work.1 According to a 1998 WHO survey of nearly 26 000 primary-care patients in five continents, 22% of those surveyed reported that sometime over the past year they had suffered persistent pain.2 Indeed, patients with chronic pain can become so desperate for relief that they go from doctor to doctor seeking help. In fact, the rise in the use of non-traditional health-care providers partly reflects the large number of patients with chronic pain, especially from headache, neck and back disorders, and arthritis, who feel they must go outside of mainstream medicine to find help, despite the fact that there is little evidence that such interventions are effective.3-5

Types of chronic pain

In general, pain falls into three main categories: acute, chronic, and cancer-related pain (panel 1). Acute pain, such as that experienced after trauma or surgery, is a normal response to tissue damage and typically resolves as the injured tissue heals or soon after. Cancer-related pain refers to pain that is the result of primary tumour growth, metatatic disease, or the toxic effects of chemotherapy and radiation, such as neuropathies due to neurotoxic antineoplastic drugs. Chronic pain is commonly defined as pain that persists for longer than the expected time frame for healing or pain associated with progressive, non-malignant disease.

Panel 1: Categories of pain

Acute pain

Chronic pain

Cancer-related pain

Duration

Hours to days

Months to years

Unpredictable

Associated pathology

Present

Commonly none

Usually present

Prognosis

Predictable

Unpredictable

Increasing pain with possibility of disfigurement and fear of dying

Associated problems

Uncommon

Depression, anxiety,

Many, especially fear of loss of control secondary gain issues

Nerve conduction

Rapid

Slow

Slow

Autonomic-nervous-system

Present

Generally absent

Present or absent involvement

Biological value

High

Low or absent

Low

Social effects

Few

Profound

Variable, usually profound

Treatment

Primary analgesics

Multimodal, largely behavioural, drugs may have a moderate role

Multimodal, drugs usually have a major role

Revised with permission from Lipman AG.6

Chronic pain may be due to the persistent stimulation of nociceptors in areas of ongoing tissue damage, for example, chronic pain due to osteoarthritis. Frequently, however, chronic pain persists long after the tissue damage that initially triggered its onset has resolved, and in some people, chronic pain presents without any identified ongoing tissue damage or antecedent intury.7 Many patients with chronic pain suffer from clinical syndromes for which there are no confirmatory laboratory studies and which are currently diagnosed on the basis of clinical criteria alone. These common chronic pain syndromes include: chronic low back pain, headache, myofascial pain syndrome, fibromyalgia, neuropathic pain, phantom limb pain, and central pain syndromes.7-9 Knowledge about the underlying pathophysiology of many of these disorders is limited.

We focus on the management of chronic pain. Portenoy and ine Lesage10 have already reviewed cancer-related pain in this series, and in the forthcoming issue Clifford Woolf and Mannion11 examine neuropathic pain. Chronic pain syndromes are frequently due to changes in the peripheral or central nervous system, in response to tissue injury (panel 2). Several changes in the peripheral nervous system occur that persist even after healing has occurred. Similarly, changes in nociceptive processing within the central nervous system can lead to persistent pain. If these changes are the source of persistent pain, surgical intervention at the site of original tissue injury is unlikely to provide relief.

Panel 2: Possible mechanisms for chronic pain

Peripheral nervous system

Sensitisation of peripheral neurons

Unmasking of silent nociceptors Collateral sprouting

Increased activity of damaged axons and their sprouts

Invasion of dorsal root ganglia by sympathetic postganglionic fibres

Central nervous system

Hyperexcitability of central neurons (central sensitisation)

Reorganisation of synaptic connectivity in spinal cord and elsewhere within the central nervous system

Disinhibition--removal of tonic descending inhibitory activity and other mechanisms

Effect of chronic pain

Whatever the cause (panel 2), the effect of chronic pain on the patient tends to be more pervasive than that of acute pain: it often profoundly affects the patient's mood, personality, and social relationships. People with chronic pain typically experience concomitant depression, sleep disturbance, fatigue, and decreased overall physical and mental functioning. As a result, pain is only one of many issues that must be addressed in the management of patients with chronic pain. Single modalities of treatment are rarely sufficient to treat chronic pain.11,12 Indeed, pain therapy that addresses only one component of the pain experience is destined to fail. Interventions that, for example, only target nociception, with nerve blocks or implantable devices, without addressing the patient's depression and social stresses are unlikely to lead to long-term benefit. In most patients, chronic pain cannot be eradicated or cured. Thus, the goal of therapy is to control pain and to rehabilitate the patient so that they can function as well as possible.

Management of chronic pain

Evidence increasingly lends support to the use of an interdisciplinary approach to patients with chronic pain. The patient receives comprehensive rehabilitation that includes multiple therapies provided in a coordinated manner.13-16 Care must be designed so that all the dimensions of the patient's condition are treated. Indeed, because of the plastic nature of the nervous system, it is frequently necessary to both rehabilitate the patient with chronic pain and remove the cause of pain, if one exists.

Interdisciplinary approach

Multidisciplinary pain management involves health-care providers from several disciplines, each of whom specialises in different features of the pain experience. The shortcoming of this approach is that access to such a range of health-care providers is usually limited and the patient's care is rarely coordinated. In the 1950s, Bonica17 developed an interdisciplinary approach designed to integrate the efforts of these health-care providers. This approach was a fundamental change from what had gone before, as Fordyce,18 wrote:

"In a multidisciplinary exercise, two or more professions may make their respective contributions, but each contribution stands on its own and could emerge without the input of the other. In an interdisciplinary effort life is not so simple. The end product requires that there be an interactive and symbiotic interplay of the contributions from different disciplines. Without that interation, the outcome will fall short of the need . . . The essence of the matter is that each of the participating professions needs the others to accomplish what, collectively, they have agreed are their objectives."

In the interdisciplinary management of chronic pain, the core team typically comprises a pain management physician, a psychologist, a nurse specialist, a physical therapist, a vocational counsellor, and the pharmacist (panel 3). The initial screening of the patient by a member of the core team determines which members of the team will be needed for a complete assessment of the patient. After this evaluation, the patient is presented to the entire core team and a comprehensive treatment plan is developed.19 The care team tailors the care plan according to the individual needs of the patient, with a focus on achieving measureable treatment goals established with the patient. The plan must fit the patient's abilities and expectations. For some individuals, education and medical management suffice, whereas for others, care may need to include an intensive rehabilitation programme that requires the patient to remain at the treatment centre 8 h a day, 5 days a week, for 3-4 weeks.

Panel 3: Roles of members of interdisciplinary pain management team

Physician

Comprehensive assessment of patient, focusing on careful neurological and musculoskeletal examination, review of past interventions, and consideration of potential medical, block, and implantation interventions.

Psychologist

Comprehensive psychological assessment, focusing on use of active coping skills and the presence of psychological illness that may affect pain experience. Development of psychological interventions, including education on the use of self-management techniques, education, and cognitive-behavioural therapy.

Nurse

Coordination of care (case management), education, and medical therapy (advanced practice nursing).

Physical and occupational therapist

Comprehensive assessment, with emphasis on the musculoskeletal system, assessment of strength, flexibility, and physical endurance, assessment of the work site and home, education on active physical coping skills, management of physical rehabilitation process.

Vocational counsellor

Assess vocational skills and identify opportunities and strategies to return to work.

Pharmacist

Comprehensive review of past and current pharmacological interventions including the use of herbal and homoeopathic substances, education of patient with regard to appropriate use of pharmacological interventions.

An open discussion on treatment goals is essential before the therapy begins. It is particularly important for the team to address the patient's expectations, since many patients may expect a complete resolution of pain and a return to full function--something that may not be achievable. In many cases, the most realistic treatment goals for patients are: the reduction, but not elimination, of pain; improvement in physical functioning, mood and associated symptoms such as sleep; the development of active coping skills; and a return to work.

The roles of team members often overlap, which underscores the importance of communication between team members. For example, while the physical therapist is responsible for education of the patient with regard to their physical rehabilitation programme, the therapist also reinforces copings skills, such as pacing taught to the patient by the team psychologist. Similarly, the nurse specialist and pharmacist must typically work with the physician to monitor the patient's response to medical management, including the management of potential adverse side-effects. All members of the team must coordinate the care so that the patient can return to work, if this is the goal of the patient's treatment plan.

Treatment methods

Pharmacological approaches--Panel 4 shows the stages involved in the drug treatment of chronic pain. The most commonly prescribed non-steroidal anti-inflammatory drugs (NSAIDs) inhibit the synthesis of prostaglandins and thromboxane by inhibition of the enzymes cyclo-oxygenase 1 (COX-1), a constitutive form of the enzyme which has an important role in the normal homoeostasis of renal and hepatic tissue, and cyclo-oxygenase 2 (COX-2), a form of the enzyme induced in inflammatory states.20 The effect of these drugs on COX-2 is thought to be responsible for their analgesic and anti-inflammatory effects. Inhibition of COX-1 is responsible for the most common side-effects of this class of drugs: gastrointestinal irritation and ulceration, blockade of platelet aggregation, renal dysfunction, and hepatic damage.21,22 Thus, long-term use of NSAIDs carries the risk of substantial adverse side-effects. Various new COX-2 specific agents are available that may reduce the risk of these side-effects.23 NSAIDs, including the new COX-2-specific agents, have a role in the treatment of some chronic pain conditions, such as the pain associated with rheumatoid arthritis. However, NSAIDs are frequently ineffective in the treatment of other types of chronic pain. Recent data indicate that COX-2 selective NSAIDs should be used in patients who benefit from chronic administration of NSAIDs. The role of COX-2-specific agents in the management of chronic pain is not yet known. Indeed, since the available COX-2-specific agents are not "pure" COX-2 drugs, they may not have as a dramatic an impact on adverse side-effects as was previously hoped.

Panel 4: Steps used during pharmacological treatment of chronic pain

History and physical

A complete medical history and physical examination must be done.

Treatment plan

A written treatment plan should state objectives that will be used to assess treatment success, such as pain relief and improved physical and psychosocial function.

Informed consent and agreement for treatment

The physician should discuss the risks and benefits of the use of the substance with the patient.

Periodic review

The physician should review the course of treatment. Continuation or modification of therapy should depend on the physician's evaluation of progress toward stated treatment objectives. The physician should monitor patient's compliance with the treatment plan.

Consultation

The physician should be willing to refer the patient for additional evaluation and treatment to achieve treatment objectives.

*Modified from current US guidelines for the use of controlled substances for the treatment of pain.19

Opioid analgesics--Although controversial, regular use of low-dose, long-acting opioids can effectively control chronic pain in selected patients.24 However, patients should be carefully assessed before the start of long-term opioid therapy. Opioids should not be used as an alternative to comprehensive care, but rather should be integrated in the comprehensive care programme when indicated. Once therapy has begun, patients on opioids need careful monitoring so that adverse side-effects can be detected and treated to ensure that the patients improve. Common adverse side-effects include constipation, sedation, rebound pain (with short-acting opioids), and impaired cognition. Although the sedation associated with opioid therapy can diminish with time, constipation often requires therapy. Addiction is a concern among patients and health-care providers. When opioids are used appropriately, addiction is rare, but patients should be monitored to ensure that they are using the opioid correctly. Assessment of patients on opioids requires the quantification and recording of specific criteria, including pain quality and intensity, activity level, and functional capacity. Guidelines specify the conditions under which prescribing of opioids is appropriate in the treatment of chronic pain.25

Antidepressants--Tricyclic antidepressants are effective for many painful conditions.26 The mechanism of analgesic action of tricyclic antidepressants is unclear, but it seems to be independent of their antidepressant effect. Tricyclic antidepressants may enhance endogenous pain-inhibiting mechanisms within the central nervous system by inhibition of serotonin and norepinephrine reuptake at the synapse. In addition to the direct analgesic effect,27 these medications can relieve other common symptoms in patients with pain, such as sleep disorder. Tricyclic antidepressants can be helpful in several chronic pain states, especially in patients with head pain (including headache), central pain, and neuropathic pain. The analgesic effect of tricyclic antidepressants usually occurs at doses lower than those required for an antidepressant effect. However, these drugs have the potential for adverse side-effects, including bothersome anticholingeric effects and life-threatening cardiovascular effects. Thus, antidepressants other than tricyclic antidepressants are commonly used in patients with chronic pain. These drugs can be effective in the treatment of a co-existing major depressive or anxiety disorder and in sleep disorder. As a result, these drugs are often an important part of an integrated pain care plan, and can improve the overall quality of life of these patients.

Anticonvulsants--Anticonvulsants, such as carbamazepine, valproic acid, gabapentin, and phenytoin, can be effective in the treatment of a range of neuropathic pain states.28 The mechanism of action of anticonvulsants for the treatment of chronic pain is unclear, but these drugs may act by stabilising sodium channels. This action may suppress firing in polysnaptic neurones within the central nervous system that process nociceptive signals. A fairly new anticonvulsant, gabapentin, has shown promise for the treatment of chronic pain and seems to have fewer potential for adverse side-effects than other anticonvulsants.28,29 Other relatively new anticonvulsants, such as tiagabine, lamotrigine, and oxycarbaxzepine, have not been studied extensively in the chronic pain population.

Other agents--There are several other drugs that are effective in the treatment of pain in selected individuals. These include autonomic nervous system agents, such as clonidine, baclofen, tizanidine, and N-methyl-D-aspartate receptor antagonists, such as dextromethorphan and ketamine. However, in spite of the advances made in pharmacological approaches to the management of pain, many patients do not respond to drug therapy trials, and alternative approaches must be tried.

Behavioural approaches

There are several behavioural approaches (panel 5) that lead to long-term reduction in pain intensity and improvement in physical functioning in individuals with chronic pain.30 As with drug and interventional approaches, these methods should be integrated into an interdisciplinary approach to the treatment of the patient with chronic pain. Cognitive-behavioural therapy is widely used in the treatment of the chronic pain.30 This psychological method attempts to change patterns of negative thoughts and dysfunctional attitudes to foster more healthy and adaptive thoughts, emotions, and actions in the patient.31 This treatment method has four basic components: education, skills acquisition, cognitive and behavioural rehearsal, and generalisation and maintenance (panel 5). Other methods of behavioural therapy are also integrated into this treatment approach. Relaxation techniques comprise a group of therapeutic approaches that allow the patient to achieve non-directed relaxation, and are effective in the treatment of chronic pain.32 Although there are several ways to achieve relaxation, one method may be more effective than another for an individual patient. Biofeedback techniques provide the patient with information on physiological functions to help in the relaxation process. Feedback information that is provided to the patient can include electromyography, electroencephalography, galvanometry, and temperature. Hypnotic techniques can help induce states of directed relaxation;30 they typically include a presuggestion component, a suggestion component, and a postsuggestion component. The presuggestion component involves the use of imagery, distraction, or relaxation to obtain attentional focusing. The hypnotist can introduce specific goals (eg, pain relief) during the suggestion component. Patients continue to use the new behaviour after the end of hypnosis during the postsuggestion component.

Panel 5: Behavioural methods used to treat chronic pain

Relaxation techniques

Deep methods

Autogenic training

Meditation

Progressive muscle relaxation

Brief methods

Self-control relaxation

Paced respiration

Deep breathing

Hypnotic techniques

Biofeedback

Cognitive-behavioural therapy Basic components

Education

Skills acqusition

Cognitive and behavioural rehersal

Generalisation and maintenance

Interventional methods

Anaesthesiologists frequently perform nerve blocks to modulate nociception. Nerve blocks are procedures that involve the administration of local anaesthetics, steroids, or neurodestructive agents centrally, to visceral plexi, or to peripheral nerves and muscles. Sympathetic nerve blocks are performed at the stellate ganglion, coeliac plexus, lumbar sympathetic chain, the superior hypogastric plexus, and the ganglion impar. These blocks are particularly effective in visceral pain states (eg, abdominal malignant disease) and in sympathetically maintained pains. Lumbar sympathetic and stellate ganglion blocks have also been used in the treatment of painful vascular diseases and frostbite to improve perfusion.

Nerve block therapy is frequently overused in the hope that it will be curative.33 However, single method of therapy is rarely curative in chronic pain. Nonetheless, block therapy may be useful occasionally as a cure in itself, but more frequently to allow the patient to take part in activating physical therapy. Individuals with chronic pain commonly have a restricted range of motion and poor physical conditioning as a result of disuse of the affected body parts and decreased physical activity. These changes can contribute to the patient's overall disability and pain experience. Although passive physical therapy techniques may provide transient relief, there are limited data available to show that these techniques improve long-term outcome. On the other hand, activating physical therapy as part of an interdisciplinary treatment approach can improve range of motion and strength, and decrease disability. Although block therapy alone is rarely curative, it can facilitate participation in rehabilitation and therefore does have a role in the management of pain.

Epidural steroid injections have been used for many years to achieve pain relief. The procedure involves placing a small amount of steroid around spinal nerve roots. The epidural steroid decreases oedema, the synthesis of prostaglandins, and spontaneous activity in C fibres. Epidural steroid injections can provide pain relief in patients with acute radicular low back pain. However, the efficacy of epidural steroid injections is not known.34 Anaesthesiologists may perform these procedures under fluoroscopic guidance to ensure that the steroid is placed in the appropriate place. Although it makes sense that the fluoroscopic approach would be more effective, no studies have been done to validate that this method improves outcome.

Trigger point injections involve injection of local anaesthetics into the trigger points associated with myofascial pain syndrome.35 This procedure seems to provide pain relief and facilitate patients' participation in activating physical therapy.

Implantable methods

When other therapies have failed, it may be reasonable to consider implantable methods of pain therapy; the two most common are epidural and intrathecal drug delivery systems and dorsal column stimulators. Both methods require surgical implantation, and, thus, carry the risk of surgical complications. Epidural and intrathecal drug delivery systems have been effectively used for the treatment of some patients with intractable chronic pain. This method has been effective in the treatment of pain associated with cancer and in the treatment of some cases of chronic pain not associated with cancer. Invasive techniques are usually used only after failure of less invasive techniques, and after a comprehensive assessment of the patient that includes careful physiological screening. Before implantation, the patient usually undergoes a trial of the technique under consideration to ensure efficacy. A retrospective review of 120 patients over a mean of 3·4 years showed that 92% were satisfied with intrathecal therapy.36 Unfortunately, others have reported that, even with a successful drug trial, 5-35% of patients do not gain significant long-term benefit from this technique.37 Many new intrathecal therapies are under investigation.

Spinal cord stimulation involves the implantation of electrodes near the spine or into peripheral nerves to modulate the transmission of pain. Spinal cord stimulation is effective in reducing radicular low back pain. In a prospective randomised trial, patients offered repeat back operation or spinal cord stimulation for failed back surgery syndrome obtained the best relief with spinal cord stimulation.37 Only 17% of the patients randomised to the stimulation group were crossed over to repeat surgery, whereas 67% of those randomised to repeat surgery crossed over to spinal cord stimulation. Despite the reduction in pain observed,however, only 25% of patients who received spinal cord stimulation returned to gainful employment. Spinal cord stimulation is widely used throughout Europe in the treatment of peripheral vascular disease and ischaemic pain. Spinal cord stimulation may also be useful in the treatment of neuropathic pains, reflex sympathetic dystrophies, and in angina38 or pelvic pain.39

Conclusion

Patients with chronic pain frequently require the attention of pain specialists, however, the management of pain is the responsibility of all providers, including the primary-care physician. Although there are limited data on how individuals with chronic pain should be treated, there are many treatment options to consider, each of which has the potential for harm. These individuals have a chronic condition that will require continual therapy with regular reassessment to obtain the best outcome. When possible, care should be evidence-based. However, care should always be focused on the patient with a goal of decreasing pain and suffering and improving physical and mental functioning.

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