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Pain management

INTRODUCTION AND OVERVIEW

One of the most common reasons for people presenting to a healthcare practitioner is the presence of pain. Many people in our community also experience persistent pain, with most studies showing that around 20% of the population suffer from some type of chronic pain problem.¹ In the past 25 years, there have been some major shifts in our thinking regarding the treatment of pain. One is an increased understanding of the biological changes that occur in the presence of pain. These include neuroplastic changes within the central nervous system that need to be addressed as part of successful pain management. The other has been the increasing prominence of a holistic approach to assessment and treatment. This has come from two directions. Pain practitioners have increasingly recognised the limitations of a purely biomedical approach to pain management. Many patients have also demonstrated dissatisfaction with this type of approach. The large number of people using complementary and alternative treatments as part of their pain management indicates the limitations of currently available treatments as well as a desire for a more holistic approach.

BOX 38.4 Complex regional pain syndrome

• Complex regional pain syndrome (CRPS) refers to regional pain usually affecting a limb. The person typically complains of generalised burning or aching pain affecting the whole limb.

• The initiating injury can often seem fairly minor and the pain out of proportion to the injury or apparent pathology.

• They may have hypersensitivity to touch (allodynia), and the distinguishing characteristics are autonomic changes including mottling, pallor, reduction in skin temperature, changes in sweating, and swelling.

• If prolonged or severe, CRPS may be associated with bone demineralisation.

• In early stages (generally < 6 months), the patient may respond to sympathetic blocks. However, often the response is poor or of short duration, and other approaches are required, including anticonvulsants, tricyclic antidepressants, spinal cord stimulation and cognitive behavioural approaches with desensitisation and a graduated exposure and exercise program.

• Referral to a multidisciplinary pain clinic is suggested.

Taking an integrative approach to pain management is more, however, than adding in alternative or complementary treatments that merely provide another symptomatic approach to the patient’s treatment. Rather, integrative medicine means taking a holistic approach to the person’s experience of pain, assessing the relative contribution of all aspects of their pain, whether physical, psychological or spiritual, and applying the most appropriate treatment that evidence has demonstrated to be effective in the management of that aspect. Integrative pain management may therefore involve the judicious use of medications, stress reduction techniques, behavioural modification and re-examination of purpose and meaning. Any or all of these approaches may need to be considered as part of the prescription that best addresses the needs as well as the desires of the person in pain.

TYPES OF PAIN

Pain is often divided clinically into acute, cancer and chronic non-cancer pain. This division reflects differences in treatment approach, although to some extent each of these aims applies to any type of pain (Fig 38.1). For acute pain, the emphasis is generally on removing the pain by identifying the cause and providing pain relief until healing occurs. In cancer pain, there is a stronger focus on pain relief, as removal of the cause of pain may be difficult. The emphasis in chronic non-cancer pain is generally on pain relief, with a stronger focus on pain management. In many chronic pain conditions, the specific cause of the pain cannot be identified with certainty, or may not be treatable. Using an acute pain approach in people with chronic non-cancer pain, with its ongoing search for a cause and removal of the pain, can be counter-productive, preventing people from accepting and dealing with their pain, and prolonging and even exacerbating their disability.

FIGURE 38.1 Aims of pain management

PAIN PATHOLOGY

BIOLOGICAL

Pain is a primary indicator of tissue pathology. From a biological perspective, pain can be divided into two pain types, based on underlying mechanisms (Box 38.1). Nociceptive pain is pain arising from pathology in somatic and visceral structures, such as bone fractures, appendicitis and renal calculi. Neuropathic pain is pain arising from pathology in neural structures, including the peripheral nervous system (e.g. diabetic neuropathic pain and postherpetic neuralgia) and the central nervous system (e.g. spinal cord injury pain and central post-stroke pain). Pain is initiated by damage or potential damage to somatic, visceral or neural tissues. However, a number of secondary changes including sensitisation at the periphery (peripheral sensitisation) and in the central nervous system (central sensitisation) are associated with trauma and the transmission of pain signals.² These secondary processes further amplify the pain experience. This means that the treatment of pain often needs to address these secondary changes as well as the underlying cause or generator of the pain.

PSYCHOLOGICAL

Psychological processes are also extremely important in the experience of pain.³ Although many texts refer to psychogenic pain, pain caused by psychological factors is rare and the term may be unhelpful. On the other hand, psychological factors invariably contribute to pain and are a large determinant of the intensity and quality of the pain experience as well as the behaviours that arise as a result of nociceptive and neuropathic stimuli. Mood dysfunction is also a very common consequence of pain. Therefore psychological factors need to be considered and assessed in any person who presents with pain.

Psychological factors fall into two main categories. Alterations in mood, such as depression, anger, fear and anxiety, may contribute to the pain problem. Our emotional state is strongly linked to activation of descending pathways from the brain to the spinal cord that control the level of amplification of pain signals coming in from the periphery. Both depression and stress-induced anxiety result in increased levels of neurochemicals that result in amplification of incoming pain signals. This results in an increase in the levels of pain that we experience. Therefore, reducing anxiety by providing reassurance and support as well as appropriate management of depression helps to relieve pain by decreasing the level of amplification of pain signals. Unhelpful cognitions such as expectation of pain, catastrophising and fear avoidance may also contribute to and exacerbate both pain and pain-related disability.

Brain imaging studies demonstrate that the perception of pain is not localised to any one brain structure or region, but involves the interaction of many regions that register and modify pain signals, including those involved with attention, mood, emotion, fear and cognition. It is therefore extremely difficult to separate the physical aspect of the pain experience from the suffering that accompanies it. ‘Pain’ can also be experienced vicariously. Empathy, or experiencing another’s pain, has been shown to produce changes in brain activity in the observer that are similar to those in the loved one who is actually experiencing the physical pain—apart from the localisation of any pain inputs.⁴

Concluding that mind and emotion affect the experience of pain does not imply that the pain is ‘imagined’ but that the relationship between pain perception and the extent of physical tissue damage is very variable. There is strong evidence indicating that the central nervous system is sensitised in many chronic pain states, and it is hypothesised that this sensitisation may be maintained by ‘sustained attention and arousal’.^5,⁶ This means that a person with chronic pain can have accentuated pain in the presence of hypervigilance, preoccupation and neuronal hyperactivity, and may go some way to explaining why emotional state has such a major effect on symptomatology for people with chronic pain syndromes. These physiological and psychological changes provide a link between mind and body and a connection between mood, cognitions and the sensation of pain. From a therapeutic perspective, helping to diminish hypervigilance and reactivity to the experience of pain may explain on a clinical and neurological level the better outcomes of people with chronic pain syndromes who include psychological strategies such as stress management or mindfulness as part of their therapeutic approach. Other reasons why the relaxation response or improving emotional state and mental health may help with chronic pain include reduction in muscle tension, the anti-inflammatory effect of stress reduction, improved responsiveness to endorphins and effects on gamma aminobutyric acid (GABA).^7,⁸

SPIRITUAL

There is very little information regarding the contribution of spiritual factors to the experience of pain. Even the concept of spirituality is poorly defined. Spirituality is not limited to the religious dimension, and many see spirituality in broad terms involving meaning, purpose and connectedness with no religious connotations. Most people would identify certain activities and relationships that give them a sense of purpose and that enrich and energise them at a deep level. From this perspective, pain can have a significant impact on a person through the disruption of these important and meaningful activities and relationships. This in turn can contribute to the physical experience of pain and add further to depression and loss of hope. However, the relationship between pain and spirituality is not all negative. For many people, the experience of pain can be an opportunity for growth as they re-evaluate their priorities, relationships and direction and find new sources of strength, meaning and hope.

ENVIRONMENTAL INFLUENCES

Pain does not occur in isolation but instead within a context that has a direct bearing on the experience of pain and the person’s response to pain. Environmental influences can be divided into three broad categories: physical, social and spiritual (Fig 38.2). Physical factors that arise from a person’s working or living situation and recreational activities may directly influence or cause pain. For example, for someone in a sedentary occupation with chronic pain, seating posture may have a large bearing on the presence of pain. Social factors such as relationships with family, friends, colleagues, employer or supervisor and cultural background can also strongly influence a person’s experience of pain and their pain behaviour. For example, the way a spouse or partner responds to a person’s pain is a major determinant of the way in which a person with pain will behave. Spiritual factors refer to non-physical, non-personal factors that may influence a person’s experience of pain. From a religious perspective, it is known that a person’s view of God affects their pain. For example, those who view God as punishing or cruel have worse pain outcomes than those who see God as forgiving.⁹ Many people without any religious affiliation also attribute improvement in their pain to an inherent, ‘supernatural’ ability of certain objects, people or a ‘higher power’. Whether these improvements are real or imagined and whether they are simply due to the physical or psychological properties of the intervention is a matter of ongoing debate and study. Nevertheless, it is difficult to consider a person’s pain from a holistic perspective without recognising and assessing the possible contribution of these factors to their pain experience.

FIGURE 38.2 Interaction between the person and their environment

ASSESSMENT OF PAIN

AIMS OF ASSESSMENT

One aim of pain assessment is first to identify the contribution of biological factors to pain, whether nociceptive or neuropathic. The distinction between nociceptive and neuropathic pain is made because the underlying mechanisms giving rise to pain appear to be different, with different pain characteristics and response to treatment (Table 38.1). Nociceptive pain is often dull or aching and, in the case of musculoskeletal pain, related to activity or position. Although not diagnostic, neuropathic pain is suggested by descriptors such as burning, electric and shock-like with pain present in a region of sensory disturbance. Neuropathic pain often occurs in the absence of stimulation, and minor stimulation such as light touch can lead to exaggerated pain (allodynia).

TABLE 38.1 Distinguishing nociceptive from neuropathic pain

	Nociceptive	Neuropathic
Symptoms	Dull, aching, worse with movement, positional Relieved by heat, rest, anti-inflammatories

Electric, shock-like, burning, unrelated to activities, associated with paraesthesia, dysaesthesia^*, numbness Signs Tenderness to palpation and/or on movement Restriction of movement Disturbance of sensory, motor, reflex function, autonomic changes Investigations Somatic or visceral pathology on imaging Neural pathology on imaging

* Dysaesthesia: unpleasant abnormal sensations, e.g. ants crawling under the skin.

It is also important to assess the contribution of psychological, spiritual and environmental factors. Assessment of psychological function includes determining disturbances in mood such as anxiety or depression. It also includes assessing the patient’s cognitions, such as their beliefs regarding the cause of their pain, their expectations and preferences for pain management, fear avoidance behaviours, lack of belief in their ability to function normally (self-efficacy), the level of relief they need in order to return to previous activities and the strategies they use to cope with their pain. Assessment of spiritual factors may be as simple as finding out what activities and relationships are important to the person and how these have been affected by the pain. This may help understand what gives them strength, purpose and meaning in their life. Further enquiries about a person’s beliefs and spiritual practices and how they influence or have been influenced by their experience of pain may also be helpful. Obtaining an environmental history focuses on elucidating any factors in their environment that may be contributing to the pain problem. It includes determining the social context of the patient, such as significant relationships, work, hobbies and activities and how these may be acting to reinforce the pain or hinder recovery.

FIGURE 38.3 Pain intensity scales

As well as the contributors to pain, assessment aims to identify the functional consequences of pain. This will almost certainly involve the whole person and include physical, psychological and spiritual consequences. For example, acute pain is often associated with physical changes such as an increase in heart rate and blood pressure, pupil dilation and mood changes such as anxiety. Cancer pain may be associated with loss of appetite, anxiety about the diagnosis, and fears and re-evaluation of hopes for the future. A person with chronic non-cancer pain may have postural changes associated with an abnormal gait, sleep disturbance, depression, fear avoidance of activities, interference with social and recreational activities, and loss of identity and meaning in their relationships and work. Although these changes may not be directly contributing to pain, they are important components of the pain problem that need to be addressed. While some may resolve or improve if the pain can be relieved, others may be persistent or severe and require separate attention.

PAIN HISTORY

Taking a patient history is usually the first step towards identifying the main contributors and consequences associated with a person’s pain problem. A history provides information that allows some direction as to whether the pain is primarily somatic, visceral or neuropathic, as well as identifying contributing psychosocial factors. For example, lumbar spinal pain precipitated by a lifting incident, that is related to movement, eased by rest, with no radiation to the legs, no numbness or paraesthesiae and a positive response to simple analgesics, including anti-inflammatory drugs, all suggest a primarily somatic nociceptive pain. In addition, sleep disturbance, loss of appetite and loss of enjoyment of activities suggest an accompanying mood disturbance.

A clear history will then provide the basis for further examination and investigations that further refine these preliminary observations. In addition, the history will provide clues regarding other aspects of the person’s presentation. The patient’s manner, tone, emphasis of certain facts, expressions and language will all help to convey important aspects of their expectations, understanding of their problem and emotional state. Although there are many variations on taking pain history, the basic elements consist of:

• history of the presenting pain problem

• previous pain management

• effect of the pain on the person (associated consequences and effect on function)

• general history (past medical, family, developmental, psychological, social, educational and vocational history) (Box 38.2).

BOX 38.2 Pain history

Pain description

• Location and radiation

• Onset—mechanism of initiating event

• Character/descriptors (aching, sharp, electric etc)

• Temporal characteristics (constant, episodic or intermittent)

• Duration (overall, and of episodes)

• Intensity (verbal—mild, moderate, severe; or numerical rating from 0 to 10)

• Aggravating factors

• Relieving factors

Previous intervention for pain

• Other pain treatments (present and past, and response)

• Pain medications and substances (present and past, and response)

Pain-associated contributors and functional consequences

• Biological (nausea, fatigue, sleep, sexual activity etc)

• Psychological (mood—anxiety, depression, anger etc; cognitions—pain beliefs, concentration, memory, fear avoidance, catastrophising etc)

• Spiritual—source of strength, effect on purpose and meaning, connectedness, beliefs etc

• Environmental (impact on and contribution of physical, social, spiritual environment)

General history

• Medical/psychological problems past and present, and family history

• Other medications including non-prescription, alcohol use and supplements, herbs etc

• Social context and important relationships

• Educational and vocational history, including worker’s compensation issues

EXAMINATION

As mentioned above, biological pain generators can be broadly divided into nociceptive or neuropathic. Therefore the physical examination can be broadly divided along these same lines into musculoskeletal (or visceral) and neurological (Box 38.3). Other body systems (e.g. cardiovascular, respiratory and gastrointestinal) may also require examination, depending on the individual’s presentation. For example, a poor cardiovascular history in a person with low back pain should alert the clinician to the possibility of an underlying vascular cause. This would then warrant careful examination of the vascular system and, potentially, further investigation.

BOX 38.3 Physical examination

Examination of pain behaviours

• Verbal cues—crying, moaning

• Facial cues—grimacing

• Movement cues—posture, guarding, limping

Examination of the painful region

• Inspection—swelling, skin colour etc

• Palpation—sensitivity to touch (allodynia), palpation of deep structures

Musculoskeletal examination

• Inspection—posture including spinal curvature, guarding, stiffness and gait

• Palpation—generalised, regional or localised tenderness over specific structures

• Movement—active and passive range of joint motion and other features such as crepitus

Neurological examination

• Sensory—assessment of large- and small-fibre function in the region of pain compared with non-painful regions using light brushing and pin prick. Consideration should also be given to the use of other modalities such as proprioception, cool (e.g. applying a metal tuning fork) and heat. Record mode (thermal, mechanical), loss or reduction (hypoaesthesia) or increased sensitivity (hyperaesthesia) and level of increase (allodynia or hyperalgesia)^*

• Motor—determine the impact of pain upon motor function and identify any possible neurological lesion. Includes muscle power (usually 5-point scale), wasting (muscle circumference), increased tone, spasm, clonus or tremor

• Reflexes—deep tendon reflexes and Babinski ’s sign

• Autonomic function—location and nature of changes in temperature, sweating, skin colour, nail and hair growth and oedema (indicative of complex regional pain syndrome; see Box 38.4).

^* Allodynia: pain in response to a stimulus which is not normally painful, such as light touch or brushing. Hyperalgesia: heightened response to a stimulus which is normally painful, such as a pin prick.

The aim of a physical examination is to identify, where possible, the nature and location of the pathology that may be giving rise to the pain. In addition, any secondary physical consequences or features of the pain, such as muscle deconditioning, allodynia or hyperalgesia, may be a focus of treatment in themselves.

INVESTIGATIONS

A wide range of investigations may be indicated to complete an assessment of a patient presenting with persistent pain (Box 38.5). Unfortunately, while most investigations can demonstrate sinister pathology (e.g. fracture, infection, cancer and progressive neurological problems), they are less helpful in identifying the specific mechanisms that may be contributing to persistent pain. For example, in patients with spinal pain, it has been demonstrated that there is a poor correlation between pain report and the presence of pathology on anatomical imaging, even using sophisticated techniques such as magnetic resonance (MR) imaging of the spine.^10,¹¹ In patients with sciatica, imaging is recommended in the acute stage only if there are ‘red flags’ such as possible infection or malignancy rather than disc herniation, or in the person with severe symptoms who does not respond to 6–8 weeks of conservative management.¹²

BOX 38.5 Investigations

Imaging

The diagnosis of pain relies heavily on imaging techniques. These include:

• X-rays (although of limited value in the diagnosis of back pain and sciatica)

• CT scan

• MRI (± gadolinium)

• bone scan (technetium).

Clinical neurophysiology

May be useful in further characterising any neurological deficit. Useful tests include:

• electromyography (EMG)

• nerve conduction studies (NCS)

• somatosensory evoked potentials (SEP).

Thermography

Significant controversy surrounds the use of this technique in the assessment of persistent pain.¹³ Differences in skin temperature can be detected by using an infrared thermometer or thermal imaging.

Thermography does not indicate the presence or magnitude of pain, but reveals alterations in skin temperature that may be due to changes in vascular or neurological function.

However, measurement of temperature differences may be useful in conditions such as complex regional pain syndrome (CRPS) to detect autonomic dysfunction.¹⁴

Therefore, in ordering further investigations, the clinician needs to be clear as to what information they will provide and whether this information is likely to be of benefit in formulating a diagnosis. In patients with persistent pain who have been adequately investigated, continuing to seek a cause for the pain may make the patient and clinician feel that something is being done. However, a non-specific investigative approach tends to yield less information over time, adds considerably to medical costs and may delay pain management and functional improvement.

MANAGEMENT OF PAIN

There are a large number of options available for the treatment of persistent pain. Sadly, however, many of these options have only limited success and many have substantial side effects. These factors have contributed to the frequent use of psychological and complementary approaches in pain management. Many of the commonly used treatments for pain are listed in the boxes and tables below. Evidence for specific treatments is discussed in the text. Rather than provide an exhaustive review of all the evidence (positive and negative) for each treatment, this text focuses on treatments that have strong (consistent positive findings among multiple high-quality randomised controlled trials (RCTs)) or moderate (consistent findings among multiple low-quality RCTs and/or one high-quality RCT) evidence to support their use.

MINIMAL INTERVENTION: IS THIS A VALID OPTION?

Before examining available treatments, it is worth considering whether it is valid to ‘do nothing’ for the person with pain. A great danger for the practitioner facing the person in pain is feeling the need to do something to relieve the person’s suffering. While this is entirely appropriate in the acute pain setting, it may actually contribute to disability in those with persistent pain. In the semi-acute phase of low back pain, it has been demonstrated that long periods of rest have little benefit. Current guidelines indicate that the best approach is analgesia, short-term rest (up to 5 days) and encouragement to return to work (see Box 38.6). Over-medicalisation of chronic pain can lead to increased dependency on pharmacological approaches, increased healthcare practitioner visits, increased passivity and little gain in either pain relief or function.

HERBAL AND HOMEOPATHIC REMEDIES, VITAMINS AND SUPPLEMENTS

Complementary and alternative therapies are widely used in the management of chronic pain, and studies indicate that more than half the population use complementary approaches for the treatment of pain.¹⁶ However, many of the studies that have been done have low subject numbers, are not adequately controlled and have variability in design and outcome measures. Although there are a large number of remedies used, stronger evidence exists for:

• willow bark (Salix alba), devil’s claw (Harpagophytum procumbens) and cayenne (Capsicum frutescens) for the relief of low back pain ^17,¹⁸

• willow bark (S. alba), Phytodolor® (a standardised herbal preparation of aspen, ash and golden rod), S-adenosylmethionine (SAMe), devil’s claw (H. procumbens), chondroitin sulfate and glucosamine (in moderate to severe pain),¹⁹ ginger extract,²⁰ capsaicin and avocado–soybean unsaponifiables for osteoarthritis^21,²²

• fish oil and gamma-linolenic acid for pain associated with rheumatoid arthritis ^22,²³

• peppermint oil for irritable bowel syndrome ²⁴

• vitamin B₁ for the treatment of dysmenorrhoea.^25,²⁶

PHARMACOLOGICAL

Although pharmacological approaches remain the mainstay of pain management (see Table 38.2), it is important to remember the holistic perspective on the management of pain. For example, where the experience of pain is being amplified by emotional, spiritual or existential concerns, the solution is to confront those issues as much as they can be and not merely to mask the problem with ever-escalating doses of medication while leaving the underlying issues unaddressed. Alternatively, providing sensitive and empathic emotional support is adjunctive to, but not a substitute for, the appropriate prescription of analgesics.

TABLE 38.2 Medications used in pain management

Drug	Indications	Side effects
Paracetamol and NSAIDs
Paracetamol	Mild to moderate pain (particularly soft tissue and musculoskeletal) Headache Dental pain Dysmenorrhoea Mild procedural pain Supplementation of opioids in moderate to severe pain

Liver toxicity in high doses (> 4 g/day) NSAIDs (including non-selective and selective COX-1 and COX-2 inhibitors)

Mild to moderate pain associated with inflammation and trauma

Back pain and arthralgias with an inflammatory component

GI upset including nausea, dyspepsia, bleeding and ulceration, headache, dizziness, drowsiness; pruritis, rash, skin reactions; tinnitus; oedema, hypertension, haematological, renal, hepatic, central nervous, respiratory system effects, hearing, visual disturbances; increased risk of thrombotic events including myocardial infarction and stroke; female infertility

Reye’s syndrome with aspirin

Opioids

Unless indicated otherwise, opioids are used for severe acute traumatic, postoperative, cancer and chronic non-cancer pain All opioids may produce constipation, respiratory depression, hypotension, urinary retention, sedation, nausea, vomiting, sweating, pruritis, hypogonadism, antidiuretic effect, biliary spasm, miosis, increased muscle tone, tolerance, dependence, decreased libido Codeine Moderate to severe pain Approximately 10% of population may be poor metabolisers of codeine; high incidence of constipation Dextropropoxyphene Moderate to severe pain Low-potency opioid with long and variable half-life. Major metabolite is cardiotoxic, and chronic high dosing may result in convulsions and psychosis. Tramadol Moderate to severe pain, possible advantage in neuropathic pain because of serotonergic, noradrenergic effects Serotonergic and noradrenergic actions. Lowers seizure threshold and possibility of serotonin syndrome when mixed with other serotonergic drugs such as MAOIs. Methadone NMDA antagonist effect. May be more effective in neuropathic pain conditions. Care required with dose adjustment because of long and variable half-life. Buprenorphine Mixed agonist/antagonist. Ceiling effect and may antagonise effects of other opioids. Pethidine

Some acute pain conditions where a short duration of action is preferable

Not indicated for the management of chronic pain

Short duration of action. Metabolite (norpethidine) accumulation and toxicity may occur. Possibility of serotonin syndrome when administered with some drugs, e.g. MAOIs. High addictive potential. Antidepressants Tricyclic antidepressants, e.g. amitriptyline, nortriptyline Neuropathic pain, fibromyalgia Contraindicated in patients with ischaemic heart disease, heart failure, cardiac conduction disturbances or a history of seizures. Sedation, weight gain and anticholinergic side effects such as constipation, blurred vision, postural hypotension, dry mouth and urinary retention. Anticonvulsants Valproate Neuropathic pain Skin reactions, gastrointestinal upset, weight gain, tremor, hair loss, liver dysfunction, haematological and teratogenic effects Carbamazepine Neuropathic pain, especially trigeminal neuralgia CNS toxicity, sedation, nausea, ataxia, diplopia, rash, bone marrow toxicity, hepatotoxicity, hyponatraemia Gabapentin, pregabalin Neuropathic pain, fibromyalgia Dizziness, sedation, ataxia, constipation, dryness of the mouth, peripheral oedema Other adjuvants Ketamine Neuropathic pain (acute or chronic episodes) Parenteral administration, narrow therapeutic window, hallucinations Antiarrhythmics, e.g. lignocaine, mexiletine Neuropathic pain Proarrhythmic effects. Drowsiness, GI upset, dizziness with mexiletine. Corticosteroids, e.g. dexamethasone, prednisone Reduction of inflammation and oedema Adverse effects with prolonged use. Local osteoporosis and joint damage with repeated intraarticular use. Benzodiazepines, e.g. diazepam Short-term relief of muscle spasm Drowsiness, memory impairment, ataxia, confusion, dependence with long-term use Clonazepam Neuropathic pain

MAOIs: monamine oxidase inhibitors; NMDA: N-methyl-D-aspartate; NSAIDs: non-steroidal anti-inflammatory drugs.

Most people with pain rely on prescription, over-the-counter or non-prescription medications for pain relief. As mentioned previously, pain is broadly divided into nociceptive (musculoskeletal and visceral) and neuropathic. The main drugs used for the treatment of musculoskeletal pain are non-steroidal anti-inflammatory drugs (NSAIDs), paracetamol and opioids.

• These are generally effective for acute and chronic musculoskeletal pain.

• Best results are achieved with ‘around the clock’ dosing rather than ‘as needed’.

• Pain is usually managed in a stepwise approach using simple analgesics for mild pain, compound analgesics and ‘weak’ opioids such as tramadol for moderate pain, and ‘strong’ opioids such as morphine, oxycodone, buprenorphine, hydromorphone, methadone and fentanyl for severe pain.

There has been a swing to increased use of strong opioids for the treatment of chronic non-cancer pain over the past 20 years based on published evidence of the low rate of addiction following short-term use of opioids. Several points are relevant to clinical practice:

• Oral morphine, oxycodone and methadone are regarded as first-line agents for the treatment of moderate to severe chronic non-cancer pain.²⁷

• Parenteral administration of strong opioids is best avoided in the management of persistent pain.

• Pethidine should be avoided because of the availability of other effective opioids, the high risk of dependence and the possibility of convulsions from the metabolite norpethidine.

• Long-acting formulations of opioids are preferable to short-acting formulations.

The development of long-acting formulations such as slow- or controlled-release agents and transdermal patches has been an advance in providing more stable levels of analgesia. However, there are an increasing number of people now maintained on strong opioids who still report ongoing pain, with few gains in function and other effects such as alterations in endocrine function. This has led to increasing concerns and debate about the wisdom of this approach and has raised several issues.

• Patients need to be warned about the risks of dependence, tolerance and driving while using opioids.

• Side effects such as nausea and constipation require appropriate treatment.

• Opioids should generally not be prescribed in those who have a history of substance abuse.

• A questionnaire (CAGE) is available which may help to identify those at risk of substance abuse (available from the Australian Government Department of Health and Ageing website ²⁷).

In contrast to musculoskeletal pain, neuropathic pain generally responds poorly to anti-inflammatory medications, and opioids have reduced efficacy. Pharmacological treatment of neuropathic pain relies on a number of other adjunctive medications.²⁸ The two main classes are tricyclic antidepressants and anticonvulsants.

• Tricyclic antidepressants are generally used in lower doses (10–75 mg) than for the treatment of depression and have an analgesic action quite apart from their mood-altering effect. They may also help with sleeplessness and comorbid depression.

• Despite the widespread use of specific reuptake inhibitors and their improved side effect profile, evidence from pain studies still indicates that tricyclic antidepressants have greater efficacy.

• Anticonvulsants have a variety of actions but broadly reduce the abnormal firing of sensory nerves that occurs with neuropathic pain. These include the older anticonvulsants such as valproate and carbamazepine and newer anticonvulsants such as gabapentin and pregabalin.

• Although cost is often an issue, use of the newer anticonvulsants with their better side effect profile is gradually replacing the use of older anticonvulsants. The possible exception to this is carbamazepine, which still is regarded as the first-line agent in the treatment of trigeminal neuralgia.

• As well as the tricyclic antidepressants and the anticonvulsants, a number of other medications and topical local anaesthetics are used but with more limited evidence of efficacy.

STIMULATION TECHNIQUES

A variety of stimulation techniques such as acupuncture, transcutaneous electrical nerve stimulation (TENS), low-level laser therapy, electromagnetic fields, spinal cord stimulation, deep brain stimulation and motor cortex stimulation are used, with varying levels of invasiveness and support. Although many studies do not provide long-term outcomes, there is positive support from at least one well-controlled trial for:

• high-frequency TENS for primary dysmenorrhoea ²⁹ and osteoarthritic knee pain³⁰

• low-level laser therapy for treatment of chronic neck pain and osteoarthritic knee pain ^30,³¹

• electroacupuncture for labour pain,³² ‘idiopathic’ headache,³³ acute dental pain and postoperative pain, fibromyalgia,³⁴ shoulder pain,³⁵ lateral epicondylitis (short-term relief),³⁶ chronic neck pain (short-term relief),³⁷ chronic low back pain (short-term relief)³⁸ and osteoarthritic knee pain.³⁰

PHYSICAL AND MANUAL THERAPIES

FIGURE 38.8 Massage therapy for back pain

FIGURE 38.7 Needle acupuncture

FIGURE 38.6 Laser acupuncture

FIGURE 38.5 Electro acupuncture

FIGURE 38.4 TENS machine/treatment

Although physical and manual therapies are widely used in the treatment of musculoskeletal pain problems (Table 38.3), there is continuing debate about their long-term effectiveness. There is stronger evidence for some approaches as indicated below:

• Spinal manipulation and neck exercises have a positive effect on cervicogenic headache.³⁹

• Physiotherapist-directed exercise and advice have significant beneficial effects on pain and function in people with subacute low back pain at 6 weeks but with only a small effect on function at 12 months.⁴⁰

• Massage has a positive effect in low back pain that is maintained for at least 12 months.⁴¹

• Heat is effective for the relief of acute low back pain.⁴²

• Exercise, spinal manipulation and interdisciplinary rehabilitation are effective for chronic and subacute low back pain.⁴³

• Physical conditioning programs that include a cognitive behavioural approach plus intensive physical training are effective in reducing disability associated with chronic back pain.⁴⁴

• Yoga has been demonstrated to be superior to exercise and a self-care book in the treatment of low back pain.⁴⁴

• One study demonstrated a positive short-term effect of therapeutic touch on tension-type headache.⁴⁵

TABLE 38.3 Biological treatments

Nociceptive	Neuropathic
Pharmacological
Simple analgesics, e.g. paracetamol, NSAIDs, opioids Antispasmodics (if spasm present) Glucosamine, herbal medicines, traditional Chinese medicine, traditional Indian medicine (Ayurveda), homeopathic remedies, naturopathic preparations, aromatherapy, vitamins and supplements, diet

Antidepressants, anticonvulsants, opioids, other adjuvants Physical

Physiotherapy, chiropractic, osteopathy, craniosacral therapy, massage

Specific techniques, e.g. Alexander, Pilates, t’ai chi, qi gong, yoga, Rolfing, therapeutic touch, reiki

Little benefit Stimulation techniques TENS, acupuncture, magnets, low-level laser therapy TENS, acupuncture, spinal cord stimulation, deep brain stimulation, motor cortex stimulation Nerve blocks

Skeletal blocks, e.g. facet joint blocks

Epidural blockade

Nerve root blocks

Surgical Nerve, spinal cord section (indicated only in cancer pain)

Dorsal root entry zone (DREZ) lesions (brachial plexus avulsion)

Other procedures provide short-term relief with high likelihood of pain returning

Spinal drug delivery Intrathecal opioids Intrathecal opioids, clonidine

Chiropractic and osteopathy are widely used treatments in the management of spinal pain. However, there is very little research that compares the two techniques or other forms of spinal manipulation.

• As indicated above, there is evidence that spinal manipulation may be beneficial in the treatment of cervicogenic headache and chronic and subacute low back pain.

• There are reports of worsening disc protrusion or cauda equina syndrome following low back manipulation, but these are extremely rare and serious adverse events have been reported to be as low as 1 per 1 million visits.⁴²

• Rotational cervical manipulation may be associated with vertebral artery dissection. Although the incidence is very low, it may be associated with serious and permanent disability and the potential benefit does not appear to justify the risk.

As mentioned previously, the experience of pain is ‘holistic’ in that every part of our mental, emotional and physical make-up is affected when we experience chronic pain. Therefore the management of chronic pain needs to address the mind as well as the body. For this reason, mind–body practices such as mindfulness, hypnosis and relaxation therapies (see Box 38.7) can reduce hypervigilance, arousal and reactivity, and reduce anxiety or depression by helping to gently shift the focus of attention. Such adjunctive techniques have excellent long-term effects in the management of chronic pain and related symptoms for those who are motivated to use them.⁴⁶^–⁴⁸

Mood is often affected by the presence of persistent pain and may need to be addressed by use of antidepressant or anxiolytic medications and cognitive behavioural approaches. Several cognitive, behavioural or mind–body approaches, including those listed below, have been demonstrated to be effective in reducing pain.

• Cognitive behavioural interventions that focus on building coping strategies such as reducing fear avoidance or catastrophising, and may take the form of individual counselling or intensive group interventions, generally have a significant impact on functional outcomes such as medication use, mood, activity levels and sleep, with less impact on pain levels,⁴⁹ and there is good evidence of moderate efficacy in chronic and subacute low back pain.⁴²

• Education regarding surgical procedures, including the nature of the procedure and the likely experience of pain, may be helpful.⁵⁰

• Relaxation techniques such as progressive muscle relaxation and self-hypnosis may be effective in reducing pain.⁵¹

• Meditation, including techniques such as mindfulness meditation, may be useful in helping patients to cope with chronic pain.⁴⁶ Its mode of action may be by reducing the preoccupation/hypervigilance and hyperreactivity that often accompany chronic pain.

• Hypnosis may reduce acute pain and labour pain.³⁸

• Attentional techniques such as imagery or focusing on the sensory rather than emotional aspects of the pain.⁵²

• Music reduces pain intensity in acute pain.⁵³

SPIRITUAL

There is wide variation in understanding as to what constitutes a spiritual approach to treatment (see Box 38.8), and very little evidence regarding the effectiveness of most treatments. Some people use the term to refer to treatments such as reiki, therapeutic touch or prayer that are believed to have a spiritual quality even when they are used simply with the aim of producing physical healing and symptomatic relief. On the other hand, spiritual approaches may refer to treatments or activities that are engaged in with the aim of addressing a person at a deeper, ‘spiritual’ level and trying to build qualities such as meaning, courage, gratitude and hope. For example, some people may find that music, art or a relationship with a higher power develops these qualities and gives them strength. People in pain can feel that they no longer have a meaningful purpose if activities and relationships they valued as important are lost or affected. It may be helpful to work with the person to develop a purpose beyond their pain which they recognise as meaningful. Using a spiritual approach then may include the process of identifying and fostering relationships and activities which strengthen a person’s spirit and provide the person with a purpose that again brings meaning and hope to their life. As mentioned previously, pain and suffering can actually be positive things by providing the person with the catalyst for change, and many people can emerge from pain and suffering with a deeper sense of meaning, strength and purpose.

BOX 38.8 Spiritual approaches to pain management

• Spiritual healing practices (e.g. therapeutic touch, prayer)

• Activities that a person finds spiritually moving (e.g. music, art therapy)

• Looking to a ‘higher power’ for spiritual strength

• Developing ‘spiritual’ qualities (e.g. gratitude, forgiveness, courage)

• Re-evaluation of meaning and purpose

SURGERY

Surgery has a major role in the treatment of pain, although results are usually poorer when the primary criterion for surgery is pain relief. Outcomes studies indicate that at 12 months there is little advantage of surgery over conservative management in the treatment of low back and sciatica.⁵⁴ Therefore, while surgery may be indicated for those with severe pain, continuing neurological compromise and disability despite intensive conservative treatment, these studies suggest that the long-term outcomes between the two groups are similar. In addition, further surgical intervention in people with chronic back pain results in a decreasing likelihood of success with possible complications such as epidural fibrosis. Therefore, the promise of pain relief with re-operation is fraught with danger.

OTHER MEDICAL AND PARAMEDICAL APPROACHES

Because of the multifactorial nature of pain, treatment is often heavily reliant on input from other healthcare professionals. The treatment of pain, and chronic pain in particular, will often benefit from assessment and treatment in an interdisciplinary setting. Pain management centres can provide a comprehensive assessment with input from appropriately qualified practitioners such as rheumatologists, psychiatrists, neurologists, anaesthetists, physiotherapists, occupational therapists, clinical psychologists, social workers, nurses and other specialties that have expertise in the underlying condition that may be giving rise to the pain. A comprehensive assessment may help to provide a holistic treatment plan that addresses the many factors involved in the pain problem. This can help to avoid the expense, frustration and disappointment that sometimes occur when people seek out a long list of various practitioners in the hope of finding the person who is going to take away their pain.

SELF-MANAGEMENT

Chronic pain is increasingly moving towards a self-management approach. Education by the primary care physician should encourage the person with chronic pain to manage the pain by themselves. Resources such as the book Manage Your Pain⁵⁵ are available which provide the patient with active coping strategies to assist them to manage chronic pain effectively, with reduced reliance on healthcare professionals and medications. Other resources such as patient information sheets on acute low back pain and other acute musculoskeletal pain problems are available and can be downloaded from the National Health and Medical Research Council of Australia website (see the Resources list below).