The key components of acute pain assessment are the pain history, the measurement of the pain and the response to any intervention (Macintyre and Schug [99]). A pain history, in addition to a physical examination, can provide important information that will help in understanding the cause of the pain and should be repeated when there is any sign of an alteration in the nature and intensity of the pain. In acute pain management, the assessment should be repeated at frequent intervals, as evidence demonstrates that regular assessment of pain leads to improved acute pain management (Schug et al. [166]). As pain is by definition a subjective experience, self‐reporting of pain utilizing appropriate assessment and screening tools should be used whenever appropriate (Schug et al. [166]). A comprehensive pain assessment includes pain location and quality, aggravating and alleviating factors, timing, duration and intensity of the pain, pain relief, and functional goals (Pasero and McCaffery [140]). The effectiveness of any previous pain treatment, as well as the effects of pain on quality of life, should also be assessed (Wuhrman and Cooney [199]).

Assessing the location of the pain and whether it radiates to any other areas of the body is one key part of the initial pain assessment and measurement. It is fundamental to the process of diagnosing the cause of the pain and developing a pain management plan (Schug et al. [166]). Patients can describe the location of the pain verbally or they can use a body map diagram (Figure 10.4) to indicate the areas where they are experiencing pain.

Many patients presenting with acute pain will have more than one site of pain; for example, complex surgical procedures may involve more than one incision site and/or multiple drain sites, and the nature and extent of pain at each site may vary. A careful assessment of the location and type of pain is required, because each pain problem may respond to different pain management techniques.

As part of the assessment process, it is important to assess the intensity of pain. Only then can the effects of any intervention be evaluated and care modified as appropriate. The simplest and most commonly used techniques for pain intensity measurement involve the use of unidimensional assessment tools such as verbal descriptor scales, numerical rating scales, faces scales or visual analogue scales. Patients are asked to match their pain intensity to the scale:

See Figure 10.5 for examples of unidimensional assessment tools.

Since many of these scales focus on assessing the intensity of pain, it is important that nurses remember to combine their use of these tools with an assessment of the patient's psychosocial needs. Regardless of which tool is used, the intensity of pain should be assessed both at rest (important for comfort) and during movement (important for function) (Gordon [68]). Most pain intensity measurement scales and tools follow these principles:

Noting the words that patients use to describe their pain is a key part of the assessment process. This may help to distinguish the underlying type of pain, such as nociceptive pain (visceral or somatic) or neuropathic pain.

Somatic pain may be described as sharp, hot or stinging; is generally well localized; and is associated with local and surrounding tenderness. By contrast, visceral pain may be described as dull, cramping or colicky; is often poorly localized; and may be associated with tenderness locally or in the area of referred pain, or with symptoms such as nausea, sweating and cardiovascular changes (Schug et al. [166]).

Features that may suggest a diagnosis of neuropathic pain include (Schug et al. [166]):

Neuropathic pain may require a specific assessment tool. Patients may describe spontaneous pain (arising without detectable stimulation) and evoked pain (abnormal responses to stimuli) (Bennett [11]). The Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) pain scale (Bennett [11]) was developed to more accurately assess this type of pain.

The SOCRATES and PQRST frameworks are pain assessment mnemonic tools commonly used by healthcare professionals to guide pain assessment. The SOCRATES framework has the following components:

The components of the PQRST framework are as follows:

Patients who have been taking regular opioid analgesics for a pre‐existing chronic pain problem or those who take recreational opioid drugs may require higher doses of analgesia to manage an acute pain episode. This is due to opioid tolerance, which is a physiological decrease in the effect of a drug over time so that a progressive increase in the amount of the drug is required to achieve the same effect (Schug et al. [166]). Additionally, patients already taking opioids are physically dependent, whereby the abrupt discontinuation or a sudden reduction in its dose leads to a withdrawal (abstinence) syndrome (Schug et al. [166]). It is therefore important to take a history of pre‐existing pain and analgesic use or recreational drug use so that appropriate analgesic measures can be planned in advance of surgery. In cases of acute trauma, undertaking a pain and/or drug history as soon as possible will help to plan appropriate analgesia. This is important for opioid‐tolerant patients irrespective of whether opioid tolerance is due to analgesic therapy or recreational opioid drug use as the pain management intervention needs to both manage pain and prevent a withdrawal syndrome. Such patients are complex and early referral to a specialist pain management service is recommended.

The key components of a pain assessment are displayed in Box 10.2.

There are many pain assessment tools that have been developed specifically for patients with chronic pain (Dansie and Turk [44]). Pain assessment tools should be used to support diagnosis and to determine the effectiveness of any treatment for the pain. Assessment tools should be easy to use and understand by patients and healthcare professionals (Cox [43]). Assessment tools for chronic pain need to be able to define the pain as well as assess the impact the pain is having on the patient's wellbeing and lifestyle. One‐dimensional tools can be suitable for the assessment of acute pain; however, in chronic pain, more holistic tools are required to facilitate a better understanding of the nature of the pain. Assessment of chronic pain needs to take these limitations into account and particular attention must be paid to factors that will modulate pain sensitivity (Table 10.1).

Other pain assessment tools have been developed to capture the multidimensional nature of pain. These specifically measure several features of the pain experience, including the location and intensity of pain, the pattern of pain over time, the effect of pain on the patient's daily function and activities, and the effect of pain on the patient's mood and ability to interact and socialize with others. Examples of these tools include the McGill Pain Questionnaire (MPQ) (Melzack [112]) and the Brief Pain Inventory, which has been validated for use in chronic non‐cancer pain (Tan et al. [174]). These are most commonly used in chronic pain assessment. Accurate pain assessment and reassessment are crucial in developing an understanding and baseline measurement of the pain, and the key is to ask appropriate questions. Particularly, questions relating to the following psychosocial elements should be addressed:

Pain assessment in vulnerable adults, for example those with cognitive impairment or dementia, and older adults may require careful consideration. There will be an increase in the older population in the UK over the next 30 years. This is anticipated to bring an increase in the prevalence of chronic pain, and with this will come the challenge of assessment of pain in many and varied settings (Schofield [165]). Older people form the population most likely to have their pain inadequately assessed, and this is especially so for patients who are elderly and have dementia (Ni Thuathail and Welford [124]). Barriers to effective pain relief for this group of patients include issues such as lack of recognition by the staff that the patient is in pain, insufficient education about pain in this group, misdiagnosis of pain and the lack of use of appropriate assessment tools (McAuliffe et al. [105]). A multidisciplinary approach to the assessment and treatment of pain is essential, but assessment in this group is a complex process that is hampered by many communication issues, including cognitive ability and sociocultural factors (Schofield [165]). A number of valid and reliable self‐report measures are available and can be used even when moderate dementia exists. The Numeric Pain Rating Scale or verbal descriptors can be used with people who have mild to moderate cognitive impairment. For people with severe cognitive impairment, the Pain in Advanced Dementia (PAINAD) (Warden et al. [192]) and Doloplus‐2 (Lefebvre‐Chapiro [95]) scales are recommended (Schofield [165]). These two scales show positive results in terms of reliability and validity. Another scale that is widely used throughout the UK is the Abbey Pain Scale, but it has not been evaluated recently (Schofield [165]).

People with learning or intellectual disabilities experience the same acute and chronic conditions as the general population, and chronic pain is often highly prevalent in this group due to associated physical disabilities and/or co‐morbidities (McGuire et al. [108]). It is not uncommon for assumptions to be made that people with learning disabilities do not experience pain and for their pain to go unassessed (Beacroft and Dodd [9], Doody and Bailey [50]), and for pain relief to be inadequate (McKenzie et al. [109]). Self‐report tools (such as describing the location and intensity of pain with numeric rating scales, verbal descriptor scales or visual analogue scales) may or may not be difficult for people with a learning or intellectual disability to use. It is important to understand that many people with mild learning or intellectual disability will be able to use these self‐report measures. However, some will lack the ability to communicate their pain in this way or lack the cognitive ability to convert their pain experience into expressive language (Doody and Bailey [50]). Assessing pain in people with more severe learning or intellectual disabilities may require the use of non‐verbal pain assessment tools and working closely with family and carers, who may recognize indicators that the person with a learning disability is in pain. Specialist pain assessment tools may need to be used, such as the Disability Distress Assessment Tool (DisDAT) (Regnard et al. [156]) or the Pain and Discomfort Scale (PADS) (Bodfish et al. [21]), which are intended to help identify distress cues in people who have severely limited communication because of cognitive impairment or physical illness.

Tools also exist for the assessment of pain in unconscious patients. Examples include the Critical‐Care Pain Observational Tool (CPOT) (Gélinas et al. [66]) and the Behavioural Pain Scale (BPS) (Ahlers et al. [2]), which provide a score based on observations such as facial expressions, muscle tension and compliance with mechanical ventilation.

Individuals are greatly influenced by each other and by the cultural groups to which they belong. Ethnic, religious and socioeconomic factors all affect the way we live in society. Pain is greatly influenced by cultural factors. Some groups are stoical regarding expressions of pain while others are more expressive, and these are behaviours that may have been learned in childhood. Disparities in assessment, analgesic requirements and effective treatment of pain exist across ethnic groups (Schug et al. [166]). The key in nursing is to ensure patients are cared for in a way that they feel comfortable with according to their cultural background. The principles that can be applied in this situation include the following (Schug et al. [166]):