ASSESSMENT AND MANAGEMENT OF CHRONIC PAIN

Miles J. Belgrade, M.D.,
Chronic Pain Rehabilitation Program
Sister Kenny Institute & Abbott Northwestern Hospital

Introduction: Chronic pain is one of the most common problems faced by physicians of all specialties; yet it is uniformly the diagnosis most shunned by care givers. The reasons for that include lack of knowledge of chronic pain assessment and lack of a strategy to deal with the many factors that contribute to the pain problem. Pain management is time consuming and chronic pain patients often have unrealistic expectations. In this essay, a strategy for case formulation and treatment will be developed and the role of pain rehabilitation will be introduced.

Definitions: Pain is defined by the International Association for the Study of Pain as an unpleasant sensory and emotional experience due to actual or potential tissue damage or described in terms of such damage. From this definition we learn several things about pain: First, it includes both sensory and emotional components; second, it may be present whether or not there is tissue damage or even the threat of tissue damage. What is universal is the idea of tissue damage making pain a high priority symptom in the mind of the person experiencing it.

Chronic pain is pain that persists far beyond the expected recovery time. Chronic pain syndrome is a condition in which chronic pain has substantially interfered with a person's ability to function in normal life roles, and has eroded the pain sufferer's self-esteem, well-being, and relationships. Understanding these terms will help us with our pain assessment. We can now assign a complexity level to the pain problem (from least complex to most complex) according to whether it is acute pain, chronic pain or chronic pain syndrome.

Pain Assessment: There are three components to a comprehensive pain assessment: Pain diagnosis base on inferred pathophysiology; identification of contributing factors; and identification of barriers. We always try to first identify what is the primary cause of pain. Based on the history, findings on examination, and the results of diagnostic testing, we infer what the cause of pain is. For example, thoracic pain due to compression fracture of a vertebral body resulting from trauma or osteoporosis or both. Typically, we don't go any farther with our assessment. Once we know the immediate cause of pain we feel we are done. That approach works satisfactorily for acute pain or uncomplicated pain. Try applying a single dimensional pain assessment like that to a case of chronic pain, or worse, to chronic pain syndrome, and suddenly we have slipped into a quagmire of failed therapies, increasing symptoms, angry, frustrated patients and weary, frustrated physicians.

Successful therapy depends on a multidimensional assessment of the pain problem that goes beyond the physiologic cause and includes the contributing factors and barriers. Contributing factors are those things which do not cause the pain in-and-of themselves, but which may amplify the pain or perpetuate it. Examples include poor posture in the chronic neck pain patient, or dietary factors in the migraine patient. Also, insomnia, anxiety and depression may contribute to an amplified pain experience. An intercurrent illness such as bronchitis with persistent cough may be a contributing factor in a patient with recent rib fracture pain.

Barriers make pain assessment harder, prevent successful application of a useful treatment, or block the recovery process. Examples should include language or cultural barriers, chemical dependency, chaotic psychosocial lifestyle, insurance non-coverage. A history of physical, emotional or sexual abuse can act as a barrier because patients with such a history may adopt poorly to a new physical injury. Medical illness can also act as a barrier: The patient with peptic ulcer disease may not be able to utilize non-steroidal anti-inflammatory drugs which would otherwise have helped the pain problem.

When formulating our comprehensive pain assessment (Figure 1), we write down first the inferred pathophysiology, then the contributing factors, and finally the barriers. From this formulation, the choice of treatments usually follows easily as we attempt to intervene on the cause, the contributing factors and, when possible, the barriers.

To help us establish the primary cause or type of pain, we must ask about the location of pain, its intensity and its quality. Severe burning pain confined to a single dermatome would suggest post herpetic neuralgia or some other neuropathic process affecting a nerve root. Multifocal pain confined to joints would favor arthritis as a cause. There are four basic types of pain: nociceptive (mechanical, inflammatory or tissue destructive), neuropathic, muscular and psychogenic.

Noiceptive implies active mechanical, thermal or chemical process which stimulates the primary sensory nerves for pain.

Neuropathic pain comes from aberrant signaling in the pain transmission or pain modulation pathways. The diabetic with neuropathy can experience pain due to spontaneous firing of damaged nerves. The location is usually in a peripheral nerve distribution or a stocking/glove distribution; or it may follow a dermatome or spinal level. The quality is typically burning and often there is a paroxysmal quality such as shooting, jabbing or shock-like pain.

Muscular pain is pulling, tight or aching. Certain movements or positions may accelerate or trigger muscular pain. The location is frequently drawn by the patient on a pain diagram in a pattern that coincides very closely with the affected muscles.

Psychogenic pain is pain that originates through cognitive and emotional processing. Examples are conversion disorder, factitious disorder, and somatization disorder.

In acute pain, a strong emphasis is placed on continual assessment of pain intensity using formal rating scales like 0-10, or a visual analog scale where intensity is marked on a 10 cm line from NO PAIN to WORST POSSIBLE PAIN. Such scales and formalized intensity ratings are important in a hospital setting where care is delivered by many, and where doses and drugs are continually changing. In chronic pain management, intensity scores play a lesser role to the role of assessing impairment, function, impact of pain and relative improvement in pain.

Pain Treatment: Pharmacological therapy alone is rarely sufficient and sometimes counterproductive in the treatment of chronic pain. In most cases, successful management requires a comprehensive approach, utilizing not only sequential drug trials but also intense physical and psychological rehabilitation. Complementary approaches such as biofeedback, relaxation, acupuncture, and hypnosis are also useful in some cases. In selected cases, regional anesthetic or neuroablative procedures have a role.

Analgesic drugs in the management of chronic pain of non-malignant origin can be divided into three groups: non-opioid analgesics, opioid analgesics and adjuvant analgesics (see Tables 1,2). Acetaminophen and NSAIDs including aspirin are in the non-opioid group. These are often used early in the course of the pain, frequently self-administered by patients in therapeutic to toxic doses. No one NSAID is a priori a more potent analgesic than another. Individual response, side effects and dosing schedule dictate the choice of NSAID for mild to moderate pain. They are a rational choice when pain is mediated by an inflammatory process. In chronic nonmalignant pain they are best used on an occasional basis only. Serious complications from gastrointestinal, hematologic and renal toxicity necessitate screening for risk factors before prescribing NSAIDs. In patients with chronic migraine, daily use of NSAIDs over a prolonged period can result in rebound headaches which present as an evolving pattern of headache into a daily syndrome with diminishing effectiveness of the offending drug and little or no response to other agents. Abstinence from the NSAID at first increases the headache intensity; but after several weeks there is a dramatic reduction in headache frequency.

Tramadol (Ultram®) is an analgesic drug that works through two different mechanisms: It is a weak mu opioid receptor agonist with about one tenth the affinity of codeine for the mu receptor. It also has properties of serotonin and norepinephrine reuptake inhibition like amitriptyline. It remains an unscheduled drug even though there are limited reports of abuse. Analgesic potency is similar to that of other weak opioids. Doses are 50-100mg every 4-6 hours up to 400mg per day. The most common side effects are gastrointestinal symptoms, dizziness, dry mouth, drowsiness and constipation. Seizures have been reported, so Ultram® is generally avoided when other factors are present that lower seizure threshold.

Tricyclic antidepressants are effective adjuvant analgesics in a wide range of painful conditions. Their analgesic effect is distinct from their effect on mood. Unless contraindicated, they should be considered in most chronic pain patients, especially in cases of neuropathic pain with continuous dysesthesias. Side effects of these drugs help us choose them for individual patients based on which side effects are minimized or advantageous. Trazodone may have adjuvant analgesic properties though there is less data supporting this. It has the advantage of fewer side effects and a better safety profile. Fluoxetine and the other selective serotonin reuptake inhibitors have not been shown to possess analgesic effects independent of their effect on depression.

Anti-convulsant drugs are also widely used in the management of neuropathic pain. We tend to use them when pain is characterized as lancinating or paroxysmal. Compared with tricyclic antidepressants, there is much less data supporting the effectiveness of anti-convulsants as analgesics. Trigeminal neuralgia is the exception, where these drugs are well established choices. Anti-convulsants are administered for pain in the same manner as for seizures: beginning with low doses and titrating up as tolerated toward a therapeutic effort or blood level. Carbamazepine is usually the first choice anti-convulsant for pain. Phenytoin, clonazepam and valproic acid are also used in the same settings. Many pain specialists and neurologists now favor the newer anti-convulsant gabapentin (Neurontin®) for managing neuropathic pain. Its use in pain is based on anecdotal reports and experience rather than on clinical trials. Gabapentin generally has less toxicity and fewer drug interactions than other anti-convulsants. Typical doses range from 300mg per day to 2700mg per day in three individual doses.

Two oral antiarrhythmic drugs, mexiletine and tocainide, are accepted in the treatment of neuropathic pain; mexiletine more so due to fewer side effects. Mexiletine, like lidocaine, blocks sodium channels and therefore inhibits transmission of impulses along injured nerves. It is considered a second line agent for painful neuropathy.

Capsicin (Zostrix®) is a novel topical analgesic which works by depleting substance P from the primary sensory nerve for pain thus inhibiting pain signal transmission. It is beneficial for chronic, localized pain states and has been studied in postherpectic neuralgia, post-mastectomy pain syndrome, monoarticular joint pain, and diabetic neuropathy. It must be applied several times daily for at least a month before evaluating its effect. Initially there can be severe burning which may limit compliance during the first couple weeks of therapy. Capsaicin vapors can irritate the airway and the cornea so that its use on the face is limited.

The Roles of Opioids in Chronic Pain: Using opioids for chronic non-malignant pain remains controversial and problematic. They are the undisputed gold standard of all analgesics and are widely used for severe acute pain. They are also well accepted as the cornerstone of drug management in cancer pain; but there are barriers to their application in chronic non-malignant pain. The barriers include fear of addiction; concern for debilitating side effects which may interfere with normal function; concern for unmanageable tolerance; lack of experience in managing opioid therapy; and fear of scrutiny by regulatory agencies.

There are no controlled trials of long-term opioids in chronic non-malignant pain. Available data in the form of case studies suggest that, in carefully selected chronic pain patients, opioids may provide substantial benefit and can be maintained for years with acceptable side effects, including a low risk of iatrogenic addiction and a manageable amount of tolerance. Common sense and our own clinical experience indicate that patients with major psychiatric disturbances limiting communication and assessment are not appropriate candidates for long-term opioid therapy. Likewise, patients with a recent history of drug abuse, or those living in a chaotic social situation are inappropriate candidates. We require that there be a clearly defined physical diagnosis consistent with the pain symptoms. All reasonable alternative therapies should have been explored adequately; and patients should not be planning a pregnancy when beginning daily opioid maintenance. These selection criteria which we have found useful are summarized in Table 3. The patient signs an agreement informing him or her of the risks and issues of opioid maintenance and laying out the ground rules for treatment. Laborious documentation is provided in the medical record detailing the decision-making process and the plan of care.

The patient's responsibilities are to be reliable about scheduled office visits, to abstain from recreational drugs, to report any emergency or acute care treatment with opioids; to guard against loss or theft of their drugs and to take their medication exactly as prescribed.

In spite of careful patient selection and vigorous monitoring, opioid maintenance for chronic pain is an arduous, time-consuming and frequently frustrating task. Abuse does occur; but in the right patient, opioid maintenance can work, allowing the patient to restore function and hope.

Pain Rehabilitation: The diagnosis of chronic pain syndrome defined above, does not represent a separate pathophysiologic entity, but represents a state of being in which persistent pain results in an eroded quality of life. Work, relationships, leisure activities, mood and spirit suffer; negative emotions increase and function declines. This diagnosis gives warning to the care-giver that simple interventions will not work. One more medication trial or one more round of physical therapy or continued chiropractic may be counterproductive by setting the patient up for failure and avoiding the necessary work of pain management. Pain rehabilitation programs provide an intensive multi disciplinary effort toward the restoration of function through physical activation, relaxation, education, and group interaction. Supervised medication withdrawal can also be accomplished more effectively during such programs. The goal of pain rehabilitation is not pain elimination, but restoration of function and spirit in spite of ongoing pain. Pain rehabilitation programs are usually three to four weeks long and may be inpatient or outpatient based. There are some important stylistic and philosophical differences among the different programs: Some will emphasize exercise over the behavioral and emotional components. Others have an operant approach and seek mainly to modify pain behaviors. Still other programs lay heavy emphasis on the elimination of all drugs as a sine qua non for optimal pain management. The best programs will maintain some flexibility and emphasize those aspects that are most needed for the individual patient. Dogma seldom produces long-lasting change. Compassionate leadership toward healthier lifestyles and more adaptive behavior will nurture pain self-management that is ongoing.

 Source: Minnesota Board of Medical Practice Update Newsletter, Spring 1997