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Understanding chronic pain

Margaret Stubbs  RGN MSc
Practice Nurse
Guildhall Walk Health Care Centre
Portsmouth

Chronic pain can persist for weeks, months and even years, seriously affecting the lives of the individuals who suffer from it. So what can health professionals do to help?

There is some controversy about when pain develops into chronic pain. Some experts define acute pain as lasting fewer than 30 days, and chronic pain as lasting more than six months. Other definitions are: 'Pain that extends beyond the expected period of healing' and 'Pain which occurs in diseases in which healing does not take place.'1,2

Chronic pain may develop where no obvious cause can be found, and it is thought to be due to changes somewhere in the nervous system.

Many people who suffer from chronic pain will have done so for months, if not years. Often, it is not linked to any tissue damage, as confirmed normally by MRI or X-ray. This type of pain can impact on many aspects of a person's life and may also be associated with functional, psychological and social problems, particularly depression, which may also involve the person's friends and family.

Some people can cope very well with chronic pain and are able to lead a relatively normal life, while others are reduced to a shadow of their former selves, finding the pain they suffer to be completely debilitating.

Diagnosis
How do we diagnose chronic pain in primary care? There are many different illnesses, conditions or injuries that can lead to chronic pain so, inevitably, there are varied presentations. However, the following general questions may be use to aid diagnosis:

  • How long has the patient been suffering from this pain?
  • Has the original injury or surgery healed?
  • What treatments have been tried?
  • What level of success with treatment has been reached?

If the pain has lasted for at least three months, and the original surgery or injury has healed, then the pain would appear to be chronic. Additionally, if treatments have been tried and lack of improvement seen, the pain may be diagnosed as chronic.

A diagnosis of chronic pain can be depressing for the patient as it indicates that there may be no long-term resolution. However, now the patient can start to make the emotional and psychological adjustments necessary for living with a chronic condition.

Chronic pain may manifest itself in a wide variety of ways, but the two main groups are nociceptive pain and neuropathic pain.

Nociceptive pain
Nociceptive pain is normally limited in duration and, when healing to the damaged organ or tissue occurs, the pain usually subsides. Arthritis is an example of nociceptive pain that is chronic. It is helpful to remember that nociceptive pain often responds well to opioid drugs and anti-inflammatory drugs. Nociceptive pain can be divided into subgroups of either somatic or visceral pain.

Neuropathic pain
Neuropathic pain tends to develop as the result of an injury or malfunction somewhere in the nervous system. As this type of pain persists well beyond the apparent healing of any damaged tissues, the pain occurs because the nervous system itself is malfunctioning. Nerves may be compressed by tumours, or damaged by scar tissue or infection.

The pain may originate from an injury, which may or may not have been caused by damage to the nervous system. Neuropathic pain may be experienced as burning, prickling, tingling, soreness, aching, stinging or numbness. Allodynia is pain resulting from non-painful stimuli. Neuropathic pain also includes phantom limb pain, nerve entrapment, such as carpal tunnel syndrome, or diabetic neuropathy.

Mixed category pain
A combination of different types of pain may occur and, as its name suggests, mixed category pain is a complex variation of elements of both types of pain. Migraine headaches are a good example of this, as is myofascial pain.

Management and treatment
Management of chronic pain involves addressing emotional and psychological health, as well as treating the physical pain. People with pain often think that healthcare professionals do not believe they really have pain. When dealing with someone who says they have chronic pain, they need their pain affirming, as it may not be obvious when first meeting that person.

Measuring pain is subjective, and does not give a complete picture of the person's pain experience. There are pain scales that can be used, but each person's pain is felt so differently; what feels like very little to one person may cause another intense distress. However, certain aspects of the pain should be assessed:

  •     When does the pain occur and how strong is it?
  •     Where is the pain felt?
  •     What triggers the pain or aggravates it?
  •     What relieves the pain?
  •     How does it impact on daily life?
  •     What is the emotional effect?

Management is about enabling the person to live with their pain as normally as possible. Initially, the hope is that treatment options might completely stop the pain; however, once the pain is acknowledged as chronic pain, the priority moves to control or management of the pain.

Primary care is most commonly where a patient will first present. It is also the place where the sufferer will come for long-term support. Management may require the involvement and support of a multidisciplinary team, which ideally should include at least two of the following: physiotherapy, neurology, psychology and anaesthesiology. To manage chronic pain in primary care, the healthcare professional must have a good understanding of the mechanisms of pain and the available medical treatments.

Nociceptive pain
There are two main classes of drug that may be used to treat chronic nociceptive pain: narcotic drugs and non-steroidal anti-inflammatory drugs (NSAIDs).

Generally, nociceptive pain responds well to the opioid class of drugs, so prescribing may be more straightforward. However, the prescribing of anti-inflammatory drugs necessitates caution, as there are risks of gastrointestinal irritation or, more importantly, gastric bleeding. Co-morbidities and their treatments must also be taken into consideration. The most commonly used drugs in this class are probably ibuprofen, diclofenac sodium (in various forms, including slow-release tablets and suppositories), naproxen, meloxicam and the current COX-2 inhibitors. The World Health Organization pain ladder is a useful guide when prescribing for chronic pain (see Figure 1).

[[Fig 1. Chronic pain]]

Narcotics are useful if pain cannot otherwise be controlled and are more often used in moderate-to-severe pain. This group of medications may be dangerous and addictive, but they can also be extremely effective. Although useful for acute pain, they have significant side-effects. Short-acting forms can lead to overuse and the development of tolerance, but the longer-acting varieties generally have fewer side-effects, and control chronic pain more effectively. If used for long periods of time without gradually reducing the dose, they may become addictive. Oxycodone, a synthetic opioid often used in the management of moderate-to-severe pain, can be effective in managing neuropathic pain. Codeine derivatives are more commonly used in postoperative pain and sometimes lead to constipation problems.

It is vital to teach the patient how to take their medication to control their pain. Waiting until the pain is unbearable has little benefit, as the medication may then take a long time to be effective and, ultimately, more medication may be necessary. Regularly spaced administration of analgesia will work far more effectively than sporadic administration. Combinations of drugs may be more effective than relying solely on one drug, but it is essential to check that the patient knows how often to take oral drugs or apply analgesic patches. Fentanyl comes as patches as well as tablets; morphine comes in varying forms and strengths; tramadol (also an opioid agonist) comes in tablet form; and all these are mainly prescribed for moderate-to-severe pain.

Neuropathic pain
Neuropathic pain is more complex from a prescribing perspective and requires more than the standard analgesic regimens. There are a number of adjuvant drugs now available. It has been found that tricyclic antidepressants, such as amitriptyline, may be effective in controlling nerve pain. The starting dose is very small to minimise any drowsiness, and is then titrated up to a therapeutic dose. Anticonvulsant medications are also effective in relieving nerve pain. These medications alter the function of the nerves and the signals that are sent to the brain.

Gabapentin and pregabalin are commonly used in dealing with painful diabetic neuropathy, again starting at low doses and then gradually titrating up to a therapeutic dose. These drugs have a number of side-effects that intensify with increasing doses and some people are unable to tolerate a dose that is considered therapeutic.

Another class of drug that may be valuable are the selective serotonin reuptake inhibitors (SSRIs), including fluoxetine and the serotonin and norepinephrine reuptake inhibitors (SNRI); particularly duloxetine (a National Institute for Health and Clinical Excellence (NICE) gold standard drug for diabetic neuropathic pain) and venlafaxine. The SSRIs and SNRIs are not as well used in the treatment of nerve pain. All these drugs must be taken on a regular prescribed regimen. Neuropathic pain very often requires referral to a specialist centre.

All the drugs used in chronic pain management may be prescribed where tolerated by the patient and co-morbidities and potential drug interactions must be taken into account. Obviously they can be continued long term, although regular monitoring by a healthcare professional is recommended.
As with nociceptive pain, narcotic drugs can be used alongside specific nerve pain medications, although NSAIDs appear to have little therapeutic effect on neuropathic pain. Tramadol often has quite a positive effect on the pain, although it should be used with caution alongside the SSRIs and SNRIs to prevent development of serotonin syndrome.

Patient self-management
Self-management of chronic pain involves the patient being willing to take regular and sometimes unpleasant drugs to reduce the pain, enabling them to undertake activities that may have been impossible during episodes of severe pain, or to return to work. The use of a Tens machine, which interrupts the pain pathway so that pain may not be felt, can be invaluable in reducing the reliance on analgesia. The use of pain relief aids, such as cushions of various shapes, can make life for the patient more bearable. Ice packs and heat pads become invaluable in helping reduce muscle spasm and its impact on pain. Activities that trigger or aggravate the pain may have to be avoided where appropriate. A key part of self-management for patients is knowing when to seek help from healthcare professionals and where to find self-help groups (see Resources).

Conclusion
Outside the primary care setting there are specialist pain management teams who may be able to assist in improving the level of pain. Primary care health professionals should be proactive in seeking out such specialist support and advice. It is important that the psychological and emotional aspects of chronic pain management are considered as, at times, the individual can feel totally overwhelmed by their pain and find it difficult to cope emotionally. The use of antidepressants to manage nerve pain may also improve mood, but depression assessment tools should be used regularly in such cases.

References
1.     Chronic Pain Policy Coalition (CPPC). About chronic pain. Available from: www.policyconnect.org.uk/cppc/about-chronic-pain
2.     Loeser JD, Butler SH, Chapman RC, Turk DC (eds). Bonica's Management of Pain (3rd edn). New York: Lippincott Williams and Wilkins; 2000.
3.    World Health Organization (WHO). WHO Pain Relief Ladder. Available from: www.who.int/cancer/palliative/painladder/en/

Resources
Pain Concern www.painconcern.co.uk
British Pain Society www.britishpainsociety.org.uk
Pain Association www.painassociation.com
Action on Pain www.action-on-pain.co.uk
Pain Coalition www.paincoalition.org.uk
Pelvic Pain www.pelvicpain.org.uk
Vulval Pain Society www.vulvalpainsociety.org.uk