Pain is a complex, subjective personal experience. It is variously described as ‘an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage’ or, more simply, ‘pain is what the patient says hurts’. These definitions make it clear that tissue damage is not required to experience pain.
In 1990, the joint report of the Royal College of Surgeons and the College of Anaesthetists highlighted the need for patients’ self-report of pain to be taken seriously. Medical and paramedical staff tend to underestimate patients’ pain, and consequently under-treat it.
Importance of pain assessment
Assessment of pain is the essential prerequisite for successful pain management. First, ask the patient about the pain intensity and believe them. While many people have anecdotes of drug-seeking behaviour, it is extremely rare compared with the number of patients with untreated pain. Second, use validated pain scales and record the findings as a baseline for the management strategy. In acute pain management, one-dimensional pain intensity scores are mainly used. In chronic pain, multidimensional scales are more commonly used. Third, after assessment, begin treatment and then reassess to gauge the degree of success. Continue the cycle of treatment and reassessment until there is a successful outcome, or treatments are exhausted.
Assessment of acute pain Despite the recommendations from the joint Colleges’ report in 1990, and good quality research showing the benefits of pain relief, acute pain is still often poorly managed. Acute pain is often seen as a short-term symptom, rather than a problem in its own right. Often no individual, neither doctor nor nurse, is willing to take responsibility for addressing the pain.
Acute pain often has an obvious cause - for example, following trauma, surgery, or the onset of a well-recognised disease process (e.g. myocardial ischaemia, pancreatitis). Acute pain may be of nociceptive or neuropathic origin. The words used to describe the pain, as well as the cause of the pain, are helpful in making the diagnosis. Pain described as burning, stabbing or like an electric shock suggests a neuropathic origin. However, lack of a diagnosis should not preclude administration of adequate analgesia while a diagnosis is sought.
In most situations, the simple model of ‘assessment, treatment, reassessment’ in combination with diagnosis and treatment of the underlying condition will resolve the problem.
Pain intensity should be measured using one of the standard one-dimensional pain scales described below. Figure 1 shows the pain chart and management plan used in the author’s hospital. It shows how a simple pain assessment can help to direct treatment plans. It also emphasises the need for stronger regular analgesia in severe pain, with a step-down in analgesia as the acute pain resolves.
Simple pain scales
Visual analogue scale (Figure 2)
This is the most common simple scale used in pain research. It consists of a 10 cm line with two anchor points of ‘no pain’ and ‘worst pain imaginable’. The patient is asked to put a mark across the line at the point that best describes their pain level. This scale is relatively simple to use, can be translated into other languages and is sensitive to small changes in pain report. The visually impaired, young children and cognitively impaired adults may have problems with the concept.
Numerical rating scale (Figure 3)
This is similar to the visual analogue scale, with the two anchors of ‘no pain’ and ‘worst pain imaginable’, but it has numbers across the scale from 0 to 10 (making an 11-point scale). This scale requires the patient to understand how to translate their pain severity into a number. This scale has similar disadvantages to the visual analogue scale, but is less sensitive in measuring small changes in intensity.
The verbal rating scale usually has four points: no pain, mild pain, moderate pain and severe pain. It is easy to use and can be used in the mildly cognitively impaired, but it is insensitive to small changes in pain intensity.
The faces pain scale is mainly used in the non-verbal or young children under the age of about 7 years. Assessment of pain in children is covered in Anaesthesia and Intensive Care Medicine 4:12: 401.
Difference between acute and chronic pain
Acute and chronic pain are often separated by the artificial time limit of 3 months. In reality, they are part of a continuum. Chronic pain is better defined as pain from continuing disease or pain that continues beyond the time expected for normal healing. Acute pain is usually short lived and of known origin. Chronic pain is often of longer duration, of unknown origin and has been difficult to treat effectively. In many cases, accurate information has been lacking and the patient and family will be fearful of the cause, prognosis, treatments and the effect on work, family life and earning capacity. Therefore, psychological factors can play a larger part in the presentation. Severe distress, rather than severe pain, is a common reason for referral to a specialist. For these reasons, multidimensional assessment tools are more commonly used in the chronic than in the acute setting.
Multidimensional pain scales
The most common multidimensional pain scales are the McGill Pain Questionnaire, and the Brief Pain Inventory, but many others are available. One of the main reasons for multidimensional pain assessment is to establish a ‘problem’ list that does not just include pain intensity, but also includes mood, behaviours, thoughts and beliefs, physiological effects and their interaction with each other. The clinician is then directed to treat all aspects of the pain experience.
McGill Pain Questionnaire
Melzack and his team at McGill University designed this questionnaire in the early 1970s. The questions are based on three domains: sensory, affective and evaluative. A fourth, miscellaneous, group was added later. In addition, there is a present pain intensity 5-point scale. The original questionnaire is long and difficult for many people to complete. A short form containing 15 words was developed in the mid-1980s. The first 11 words describe the sensory dimension and the next four the affective dimension. A visual analogue scale and a present pain intensity scale are also included in the short form.
Brief Pain Inventory
This assessment form is often used and has been translated into several languages. It initially assesses pain intensity at its worst, best and at the time of the evaluation. It further assesses the percentage relief from current medications or treatments, and the duration of the relief. It enquires about exacerbating and relieving factors. Aspects of pain belief are evaluated and the level of interference with normal daily living is assessed. A short version of the Brief Pain Inventory is also available. Its disadvantages are that it is a lengthy form to complete and it is unsuitable for those with cognitive impairment.
The Memorial Pain Assessment Card
This was developed as a rapid multidimensional pain assessment tool in cancer patients and uses three separate visual analogue scales to assess pain, pain relief and mood. The card also has a set of adjectives for pain intensity. This measurement tool has the advantage that it takes very little time to administer and that the results correlate with other, longer evaluators of pain and mood. The card should be folded so that only one scale is presented to the patient at a time.
Neuropathic Pain Scale
This is a specific assessment tool for neuropathic pain developed by Galer and colleagues. It uses eight pain descriptors or pain quality items (sharp, hot, dull, cold, skin sensitivity, itching, deep and surface pain), plus a global measure. It also measures unpleasantness, using a scale of 0 to 10.
The Leeds Assessment of Neuropathic Symptoms and Signs (LANSS)
This was developed by Bennett. It is described as a tool for identifying patients in whom neuropathic pain mechanisms dominate their pain experience. It is based on five clinician-directed questions and a relatively simple bedside examination of sensory dysfunction. The clinical examination consists of a cotton-wool test for allodynia and a pin-prick test with graded-weight needles. The author achieves specificity of 80% and sensitivity of 85% with this assessment tool.
Specific difficulties with pain assessment
Cognitively impaired older patients: verbal reports of pain by cognitively impaired older adults should be acknowledged. Behavioural tools are advocated for those who are cognitively impaired and unable to report pain verbally. There appears to be no single tool appropriate for assessing pain in all cognitively impaired older adults, and more research is needed to validate the effectiveness of the assessment tools available. Behavioural assessments appear promising but have yet to see widespread use.
Fear of prescribing to opioid abusers often leads to inadequately treated pain. However, the nature of the lifestyle of abusers means that they are more likely to suffer chronic painful conditions than the general population. Assessment and treatment are particularly difficult in this group and referral to specialists is recommended.
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