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Dr Andrew Lawson is a Consultant in Anaesthesia and Pain Management at the Royal Berkshire Hospital and Senior Clinical Fellow in Medical Ethics at the Medical Ethics Unit, Imperial College School of Medicine. Dr. Lawson is also Chairman of the Pain Intervention Interest Group (Pain Society UK). His e-mail address is: Andrew.Lawson@rbbh-tr.nhs.uk

'All the happiness mankind can gain, is not in pleasure but relief from pain'. 

Introduction 

Dryden, who is quoted above, hit the nail on the head. Untreated pain remains one of our greatest fears. Despite recent great advances in pharmacology and the understanding of pain, some patients’ lives are still troubled by pain It would be foolish to suggest that all pain can be abolished at all times - but in up to 80% of patients pain can be managed, quality of life restored and the ability to function rejuvenated. This can be achieved with appropriate prescription of drugs and other pain management techniques.  

It continues to dismay me that patients who are suffering often do not seek help. Patients sometimes do not want to bother their doctor as they feel that 'nothing can be done' or that suffering is a normal part of their disease. Being sick does produce suffering of many types but as far as pain is concerned there are vanishingly few occasions when nothing can be done. My message is that patients should be encouraged to seek further help if their pain is uncontrolled or if the side-effects of the painkillers are worse than the pain. This is a problem that we occasionally see in the management of pain after surgery, where effective pain relief comes with such bad nausea that the patients would rather suffer the pain than experience the sickness! Changing to different painkillers or using different anti-sickness drugs can often solve the problem. The solution lies in knowledge of alternatives and it has to be said, thinking beyond our expectations.  

What is pain?  

The meaning of pain has troubled philosophers for hundreds of years. More recently it has been defined as ‘an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage’.[1 ]So pain may exist in the absence of disease. Occasional episodes of pain are part of normal life and pain is an important symptom of illness. We experience pain as part of a warning mechanism. It makes us, for example, remove our hand from a flame without thinking and warns us that part of our body has been damaged. This basic form of pain serves a sound evolutionary purpose to keep us safe and not having it can be disastrous. This type of pain is termed nociception - it is the sort that you get after surgery and with some types of cancer and is pretty much amenable to treatment. Nociception is caused by chemical, mechanical, or thermal stimuli, which cause nerve endings in our bodies to tell us ‘it hurts’. 

Damage to any nervous tissue can also produce pain which is called neuropathic pain. This sort of pain is associated with burning sensations, shooting pains and with sensory changes in the affected area. If you have ever fallen asleep in an unusual position and woken up with a numb arm or leg which then, as sensation returns, feels unpleasant, you have experienced something like neuropathic pain.  

Whilst attention to the underlying cause is part of proper management, when pain persists this symptom itself has become part of the disease process and not just a secondary problem. In many respects pain management is similar to palliative care. The symptom of ‘pain’ is palliated but the underlying disease process is unaltered. However, contemporary thinking suggests that persisting pain states are themselves a disease entity. Persisting pain is associated with alterations in the hormonal balance in the body along with changes in clotting mechanisms, alterations in mood, sleep deprivation and psychological problems. These secondary effects can themselves cause health to worsen so treating pain is not just symptom relief, but can produce more generalised therapeutic benefit.  

It is important to remember that ‘pain’ is more that just a sensation. If you are anaesthetised you cannot feel pain but were we to look at the brain activity of an unconscious patient we could see a response to a surgical stimulus. The experience of pain is more than just a sensation, it is a conscious experience and thus there are profound effects of pain on the mind and conversely the mind can be recruited to help control pain.  

How do we feel pain?

We experience pain in our consciousness.  We integrate the sensation of nociception or neuropathic pain with our emotive responses and our memories of what the pain signals to us. The pain is localised to an area by the cerebral cortex in our brain. The 17^th century philosopher, Descartes, thought that there was an anatomical pain pathway for pain. If we burned ourselves on a fire the particles of fire would travel to the brain, causing us to feel pain as though ringing a bell in our mind.

We now know that there is no discrete pathway for pain but that there are a series of interactive biological mechanisms that transmit the sensation (Figure 1) of heat (A) via cells that detect the presence of damage or potential damage (B). These cells send information through nerves to the spinal cord (C), thence to the brain (F) where we experience the pain.   

We can explain how we manage pain in the 21^st century with reference to the 17^th century model of Descartes. We can remove the cause (extinguish the ‘fire’ A by using surgery, radiotherapy or chemotherapy). We can alter the way that pain receptors are stimulated by, for example, suppressing inflammation using steroids or non-steroidal anti-inflammatory drugs (NSAIDs) – see later. The painful stimulus can be interrupted in the nerve by nerve blocks or in the spinal cord (C). The pain signal can be ‘flooded’ by counter stimulation such as with a TENS (trans cutaneous electrical nerve stimulation) device (see later), which may act at B or C. Or the perception of pain can be changed by drugs such as morphine acting in the brain (F).  

Assessing how it feels 

When a doctor or nurse makes an assessment of pain it is dependent upon the patient reporting the degree of pain; pain is what the patient says it is, as all pain is personal and subjective. The impact of pain is related to our mood, to its context, and to our general physical health. For example, the pain of childbirth, though intense, may not produce as much fear as the pain of bone cancer. The knowledge that pain will go away may make it more bearable for some patients, the fear that it will not may make it much worse. Pain is also worse after a bad night’s sleep or if there is associated anxiety. This subjectivity and variability can make pain difficult to assess and treat and it is a challenge for health professionals. Complete, regular and repeated assessments with realistic objectives are required. Often doctors will use a Visual Analogue Pain Scale to assess pain and measure the effects of treatment. The patient is asked to rate his or her pain on a scale from 'no pain' to 'worst imaginable pain' and this can be read off the line as a score.  

Using such a scale can show the effects of both pain treatment and treatment aimed at the underlying cause (putting out Descartes' fire). Treatment should be patient focused and tailored to individual needs. 

While the focus for patients and their carers would naturally tend to be on pain levels, important issues such as quality of life and ability to function need to be borne in mind too.

General Principles  

Empathy, understanding, diversion and elevation of mood are essential adjuncts to the effective use of analgesics (painkillers).[2]  Where at all possible, the cause as well as the symptom should be treated. For example, we would fix a broken leg as well as giving painkillers. There are times when doctors cannot find the exact cause of the pain, even so something should be done to make the person more comfortable and make the pain easier to live with. Measures to control symptoms should not be delayed whilst a diagnosis is made.  

Proper advice about posture and positioning along with diet and occupational therapy may be as effective as other aspects of care. It makes no sense to simply abolish pain at the expense of side-effects when other simple measures may be as effective. This is particularly so when pain is only present on movement. It is also vital to remember that if a patient has pain from one cause, say for example a pelvic tumour, this does not exclude other causes of pain.  An episode of acute low back pain may be entirely unrelated to the underlying disease - people with malignant disease slip discs and strain their backs too.  

Most hospitals now have pain control teams. Where post-operative pain becomes a problem or pain management becomes complex these teams can help to improve pain control.  

Treating Pain  

Drugs

Broadly speaking painkillers are divided into those that are opioid based and those which are not:

NSAID - non-steroidal anti-inflammatory drug; opioid - opioid painkillers are those which may be naturally occurring and derived from the opium poppy such as morphine or synthetic such as pethidine.  

The nature of the pain is an important guide to treatment. How we experience the pain is a guide to its cause and its treatment. So taking a pain history is an important aspect of assessment. 

Sensory changes in the area that is painful and the symptom of pain produced by a non-painful stimulus (called allodynia) are characteristic of neuropathic pain.  In general terms neuropathic pain is treated using adjuvant painkilling drugs (something that doesn’t necessarily work directly on the pain, but aids the process of pain relief - see later), whereas nociceptive pain is treated with paracetamol, NSAID's and opioids. There is however much overlap and clinicians are increasingly realising that neuropathic pain may respond to opioids.  

Where pain is continuous, as is often the case in malignant disease, three principles guide drug therapy: giving drugs regularly by the clock to avoid recurrence of symptoms; preventing side-effects in advance of their occurrence such as by giving anti-sickness tablets in anticipation of nausea, and providing drugs by mouth unless otherwise indicated.  

In the initial stages of pain management the first step should be to gain control of the pain using rapidly acting painkillers. Once control is achieved then slow release or continuous delivery formulations of drugs may be substituted where appropriate.  

The World Health Organisation has proposed an 'analgesic ladder' where there is a stepwise increase in the strength of painkillers prescribed as pain intensity increases.  Whilst using this ladder is standard practice there is increasing realisation that in some patients using weak opioids produces inadequate analgesia with unwanted effects and that small doses of strong opioids may produce better pain relief. Adjunctive therapies (see later) include corticosteroids, antidepressants and anticonvulsants. These drugs principally have indirect methods of producing pain relief.

Non Opioid Pain Killers 

Paracetamol (acitaminophen)

Paracetamol is used extensively both alone and in combination with weak opioids. It has excellent pain relieving properties and reduces fever but is unlikely to be effective alone against anything other than mild pains. It is relatively free of gastrointestinal side-effects. Its exact mode of action is unclear but it blocks the action of some of the chemicals known as prostacyclins which are involved in inflammation and pain sensation.  

Non-steroidal anti-inflammatory drugs

This group of drugs includes non-prescription drugs such as ibuprofen and prescription-only drugs such as celecoxib. There are over thirty such drugs available and they all exert their action by blocking the production of prostaglandins. Prostaglandins are biologically active fat-like molecules. NSAIDs are involved in inflammatory responses, the production and perception of pain and in the regulation of blood flow in the stomach lining and the kidneys. They are painkillers of varying intensity but all have the potential to produce gastric bleeding and kidney problems.  

Drugs for neuropathic pain

Gabapentin

As well as the antidepressants a variety of other medications have been tried to treat ‘nerve pain’. Carbamazepine and sodium valproate (which are anticonvulsants) have been the agents of choice for many years but gabapentin, which has a reasonable side-effect profile and has been documented to be effective in a wide range of neuropathic pain states, is considered by many to be the drug of first choice. Gabapentin is the only drug of its kind to have a specific product licence for the treatment of nerve pain.  

Other agents

Infusion of local anaesthetics and drugs such as NMDA (N-methyl-D-aspartate) antagonists, an example being the anaesthetic agent ketamine which affects the transmission of pain, have also been tried in severe neuropathic pain. These treatments are generally limited to specialist centres due to logistical factors and problems with side-effects. Ketamine has been used along with other anaesthetic agents in palliative care units.  

Adjuvant drugs 

Corticosteroids

Steroids reduce tissue swelling and are used extensively in cancer pain management and in the management of pain where acute inflammation seems to be a significant problem such as in acute sciatica due a prolapsed disc.  Where lymph nodes are swollen and pressing on nerves causing neuropathic pain, or where radiation has produced inflammation of nerves, steroids may be effective. Steroids reduce swelling around nerves and suppress the formation of chemicals which stimulate pain receptors; they also reduce spontaneous pain in excitable nerve tissue. They can be administered both by mouth and also by direct injection around swollen tissue. Steroids, when given acutely or for short periods of time, are not generally associated with serious side-effects.  

Antidepressants

Antidepressants have been prescribed as adjuvant painkillers for over thirty years. Evidence has demonstrated that they are effective in treating nerve pain but they are commonly prescribed in patients with persisting pain as a co-analgesic. They do not exert their effect by removing depression but possibly have some effect on pain transmission in the spinal cord or in the brain. In many patients, when taken at night, they seem to help re-establish a normal sleeping pattern and this of itself may be beneficial.  A common complaint of patients with continuous pain is sleep deprivation which, when severe, may produce anxiety, depression and daytime sleepiness.

Opioid Drugs  

Opium derived and synthetic opium-like drugs (opioids) remain the mainstay of management of all but moderate pain. These drugs share the common properties of pain relief, mood changes, changes in pupil size and a degree of respiratory depression. They can all produce nausea and vomiting, constipation and changes in blood pressure.  Some tolerance to the wanted and side-effects of the drug occurs.  

This class of drug acts by mimicking the effects of chemicals made by the brain which produce pain relief - the ‘endorphins’. The drugs act on a variety of specialised areas in the body, the ‘receptors’ to produce both desired and unwanted effects.  

Weak opioid drugs such as codeine and dihydrocodeine are usually prescribed for mild to moderate pain. There is little to be gained by giving large doses of weak opioid drugs or multiple drugs when pain is severe. When pain is severe and not helped by weak opioids a strong opioid should be used.  Starting doses will vary from patient to patient but in essence the correct dose is that which is enough to contain symptoms without unacceptable side-effects.  

Individuals vary in their response to differing opioids so if analgesia is produced with unacceptable side-effects then changing to another drug at an equivalent dosage is an appropriate next step. The most popular opioid drugs are long-acting morphine preparations given by mouth. The dose is calculated after dosage titration (an assessment process) with a short acting preparation or by working out what the equivalent dose of morphine is for a given dose of codeine for example. Recently opioid delivery systems have been introduced for administering drugs across the skin through a patch which is changed every three days. These systems have been shown to be effective with a seemingly lower side-effect profile in some patients. Methadone is an effective painkiller and has the advantage of a single daily dose and possibility of being more effective than other opioids in neuropathic pain. 

Complementary therapies                     

TENS and acupuncture have both been advocated for the treatment of pain. These treatments are widely used and whilst the effectiveness is unlikely to be that of standard analgesics they are useful adjuncts to standard therapies. 

Relaxation techniques and massage all promote well being and reduction of anxiety and may also reduce muscle spasm. Pain relief may thus be helped by both primary and secondary approaches.   

Pain clinics and pain programmes                           

Up to 80% of patients with pain due to malignant disease should be able to be managed without referral to specialist pain units. Nonetheless some patients will experience persisting pain despite appropriate primary management.  If the fire in Descartes’ model of pain cannot be extinguished then pain clinics offer a resource for patients.  

Pain specialists offer advice about opioid rotation and switching to uncommonly used opioids as well as the expertise for nerve blocks and other interventional techniques for pain control.  

In some circumstances repeated nerve blocks can reduce the requirement for other drugs for pain control, and in a few circumstances destroying nerves with nerve poisons, temperature or cold can produce long periods of pain reduction.  There are similarly some circumstances where drugs can be administered directly onto the spinal cord or through the epidural space to provide continuous pain relief. Whilst these occasions are few in number, in well chosen patients the results can be dramatic.  

Many pain clinics can offer pain management programmes which are mostly based on cognitive behavioural therapy models. These programmes are aimed at coping with the effects of pain on the individual and reducing its negative effect on the patient rather than by primary reduction in pain. Even so, where a degree of pain relief has been achieved, improving management strategies along with coping mechanisms can provide additional benefit to patients. 

Unsound fears of addiction 

A man was sent to me many years ago with a chronic pain in his pancreas. I eventually persuaded him to try some strong morphine-like painkillers, which did the trick. He was not keen to take them as he had a fear of becoming addicted. This man had symptoms that were not going to go away, were not curable but could be treated by taking drugs. Someone being treated for high blood pressure would not be too worried about taking blood pressure tablets forever. They would not feel guilty or fear being thought weak-willed if they needed more tablets for their blood pressure, nor would they be weaned off them as soon as their blood pressure came down. Pain is different it seems, but it is hard to understand why. 

This fear of addiction by patients and worry about addiction by doctors has permeated our attitudes to pain and its treatment, but we should not use the minimal risk of addiction as an excuse to under-treat pain. Opioids remain the most effective and simplest method to control severe pain. 

Conclusions 

Long-term, untreated pain can cause feelings of hopelessness and depression, as well as making people feel isolated. An independent panel of experts, established to provide advice to the NHS and UK health ministers, the Clinical Standards Advisory Group, reported to the government in 2000 on the way in which specialist pain services were being delivered and advised on standards and availability of care for NHS patients with acute and chronic pain. The report said that a great deal could be done to treat pain and to alleviate its effects on people's quality of life[3].  

Techniques to manage pain are improving all the time so it is important if you are feeling pain to tell your health professionals - ‘don’t suffer in silence’ – the more you tell them the more likely they will be able to help. There is a wealth of information on pain management available on the internet and you can use it to inform your discussions with your doctor.  

Dr. Lawson has provided the Helpline with a list of useful websites and further references relating to information in this article. Please call the Helpline if you would like these details. 

Frequently asked questions  

Q. If I take morphine will I become addicted?

A. There is no serious risk of addiction when morphine-like drugs are given for pain control.  

Q. If I take morphine will it mask any new disease and prevent my doctor from treating me properly?

A. No. Though an increase in the strength of drug needed to control pain may be a harbinger of new disease, treating pain does not prevent diagnosis.  

Q. If I can manage without painkillers am I better off by just putting up with the pain?

A. No. Evidence suggests that just tolerating the pain is physically bad for you.  

Q. If I resort to morphine-like drugs will my life expectancy be shortened?

A. The opposite is probably true, good control of pain will increase life expectancy. 

Q. Is it true that nerve blocks cannot help pain caused by cancer?

A. No. In certain circumstance they can give dramatic improvements.  

Q. Why is my pain worse at night?

A. Probably because you are less distracted and likely to notice it more.   

Q. If my doctor wants to start morphine does that mean nothing more can be done to fight the disease?

A. No. Getting good control of pain goes hand in hand with treatment. 

Q. What if I cannot swallow tablets?

A. Pain killers also come as liquids, in lozenges that dissolve under the tongue, as lollipops, as suppositories and as patches which act through the skin. 

Q. Won’t morphine make me feel sick, drowsy and unable to function or drive?

A. There are ways to deal with side-effects and there is some evidence that driving with effective pain relief is safer than driving in pain*.

* The Drivers Medical Group (tel: 0870 600 0301) of the Driver and Vehicle Licensing Agency (DVLA) and your car insurer may need to be informed about your medical condition and/or your treatment.