Pain Assessment

Updated: Sep 27, 2018
  • Author: Stephen Kishner, MD, MHA; Chief Editor: Erik D Schraga, MD  more...
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Overview

Practice Essentials

Precise and systematic pain assessment is required to make the correct diagnosis and determine the most efficacious treatment plan for patients presenting with pain.

Technique

Pain must be assessed using a multidimensional approach, with determination of the following:

  • Onset: Mechanism of injury or etiology of pain, if identifiable

  • Location/Distribution

  • Duration

  • Course or Temporal Pattern

  • Character & Quality of the pain

  • Aggravating/Provoking factors

  • Alleviating factors

  • Associated symptoms

  • Severity: Intensity or impact on function, sleep, mood

  • Barriers to pain assessment

Pain scales

Pain measures may be categorized as either:

  • Single-dimensional scales - These scales assess a single dimension of pain, typically pain intensity, and through patient self-reporting. These scales are useful in acute pain when the etiology is clear; see the image below

    Faces Pain Rating Scale. Faces Pain Rating Scale.
  • Multidimensional scales - These measure the intensity, nature, and location of pain, as well as, in some cases, the impact that pain is having on a patient’s activity or mood; multidimensional scales are useful in complex or persistent acute or chronic pain

Pain assessment in the elderly

Pain assessment can be particularly difficult in elderly patients for the following reasons:

  • Underreporting of discomfort because the patient does not want to complain or due to communication or cognitive impairment

  • Other medical comorbidities may overshadow pain complaints

  • Decreases in hearing and visual acuity, so that pain assessment tools that require extensive explanation or visualization to perform will be more difficult and possibly less reliable

The verbal descriptor scale may be the easiest tool for the elderly to use. It allows patients to use common words to describe what they are feeling.

Pain assessment in infants

The following tools use a combination of behavioral and physiologic measurements to assess pain in infants:

  • CRIES - Uses 5 variables (ie, crying, requires oxygen, increased vital signs, expression, sleeplessness) on a scale of 0-2 points to assess neonatal postoperative pain [1]

  • Modified Behavioral Pain Scale - Uses 3 factors (facial expression, cry, movements); has been validated for children aged 2-6 months [2]

Pain assessment in young children

Limited cognitive or language skills may influence pain measures, as may the positive or negative consequences of a child’s behaviors associated with pain.

In children older than 3-4 years, self-report measures may be used. However, children may underreport their pain to avoid future injections or other procedures aimed at alleviating the pain.

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Overview

Background

Precise and systematic pain assessment is essential to make an accurate diagnosis, and thus establish the most beneficial treatment plan for patients presenting with pain. Pain is not always pathologic, as it may serve a protective role. Humans evolved the mechanisms to perceive and respond to pain in order to be aware of and react to injury. [3] However, pain is not always correlated with tissue damage and can persist long after the time for normal tissue healing.

Pain is defined by the International Association for the Study of Pain as "an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage." [4] Pain is a subjective and unique perceptual experience with multiple dimensions that may not be directly observed by others or measured by physiological tests. Pain assessment depends significantly on self-report. [5] Much effort has been put forth in evaluating and improving self-report methodology within the field of human pain research. [5, 6]

The Joint Commission on Accreditation of Healthcare Organization in the United States has requirements for hospitals to have defined criteria to screen, assess, and reassess pain that are individualized with the patient’s age, condition, and ability to comprehend. Pain assessment should be ongoing and documented. Reassessment is important to gauge response and to monitor for side effects of treatment. [7] Patients should be asked to describe their pain in terms of the following characteristics: location, radiation, mode of onset, character, temporal pattern, exacerbating and relieving factors, and intensity. The Joint Commission updated the assessment of pain to include focusing on how it affects patients’ function.

The subjectivity of pain inherently makes it difficult to study and measure. It has been stated that an ideal pain measure would be sensitive, reliable, accurate, valid, and useful in both clinical and experimental situations, and able to distinguish between the sensory and emotional aspects of pain. [3]

Pain Etiology

Different disease processes may present with similar pain characteristics. Vascular and neurogenic claudication symptoms are a classic example. However, patients with similar pathology may describe different types of pain or may have no pain at all (eg, spinal cord lesions, diabetic neuropathy). The history and physical examination can assist in distinguishing these subtle differences. The determination of pain type is important because different types of pain tend to respond to different treatments. [6]

Nociceptive pain refers to pain due to an actual or potentially tissue-damaging injury that is transduced and transmitted via nociceptors. [4] Nociceptors are found in all tissues except the central nervous system (CNS). The pain is typically proportional to the degree of injury or activation of afferent nociceptive fibers and can be acute or chronic (eg, somatic pain, cancer pain, postoperative pain). [6]

Neuropathic pain is defined as pain arising as a direct consequence of a lesion or disease of the somatosensory system. This definition does not include all nervous system lesions that may result in pain. A purely upper motor neuron lesion that results in spasticity and muscular pain is not considered neuropathic pain. Neuropathic pain may be classified as occurring in the central or peripheral somatosensory nervous system. [4, 6]

Deafferentation pain is chronic and results from cessation of afferent input to the central nervous system. The pain may arise in the periphery (eg, peripheral nerve avulsion) or in the central nervous system (eg, spinal cord lesions, multiple sclerosis). [6]

Radicular pain is a type of neuropathic pain due to ectopic impulse generation evoked by stimulation of nociceptive afferent fibers in spinal nerves, their roots, or ganglia. It is distinct from radiculopathy, but the two often coexist. Radiculopathy denotes the objective loss of sensory and/or motor function as a result of nerve root injury. [8]

Central pain arises from abnormal function or a lesion in the central nervous system. This may occur with lesions involving the spinothalamic cortical pathways (eg, thalamic infarct). The pain is usually constant with a burning, electrical quality. It is exacerbated by activity or changes in the weather. Hyperesthesia and hyperpathia and/or allodynia are invariably present, and the pain is highly resistant to treatment. [6]

Psychogenic pain is inconsistent with the likely anatomic distribution of the presumed generator, or it exists with no apparent organic pathology despite extensive evaluation. [6]

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Technique

Approach Considerations

The history of pain or “pain history” is the physician’s initial tool to assess a patient in pain. A detailed history and physical examination is essential, not only to narrow the diagnoses but also to guide further diagnostic studies, if appropriate. Pain of unknown origin should always be considered a potential emergency and the physician should remain vigilant for signs of an urgent situation. A concise initial history can help identify possibly critically ill patients presenting with pain. Not all aspects of the pain history are required after the diagnosis is clear, if it would limit timely treatment and prolong patient suffering.

Pain Assessment

Pain must be assessed with a multidimensional approach, as follows:

  • Onset: Mechanism of injury or etiology of pain, if identifiable

  • Location/distribution

  • Duration

  • Course or Temporal Pattern

  • Character and Quality of the pain

  • Aggravating/Provoking factors

  • Alleviating factors

  • Associated symptoms

  • Severity: Intensity or impact on function, sleep, mood

  • Barriers to pain assessment

Onset

Recognizing the inception of pain can be crucial in determining proper treatment. The onset of pain may be described as abrupt and sudden or insidious and gradual. If applicable, the mechanism of injury can direct the clinicians in the correct path of diagnosis if there is trauma involved, especially if the symptoms are acute.

Often, however, the mechanism of injury is not apparent. Chronic degenerative conditions and many neuropathies present insidiously. The mechanism of injury is not as obvious in some acutely presenting conditions, such as with autoimmune diseases or mass effect from a neoplastic process. Any changes, new medical conditions or surgical procedures around the onset of pain should be documented.

Location/distribution and anatomical etiology of pain

The location and distribution of pain can be very helpful with narrowing the diagnosis. Pain may be localized to injured anatomic structures, especially with somatic nociceptive pains that occur with musculoskeletal injuries. Neuropathic pain is typically confined within the sensory distribution of the affected nerve or nerves. This can be in the distribution of a peripheral nerve(s), plexus or roots, or in a central topographic pattern. [9] Pain may be more diffuse or in a stocking-glove pattern as in the case of a generalized peripheral neuropathy. Pain may migrate or radiate from the source generator of pain to other body areas. If pain is diffuse, the physician should try to localize the area of maximal pain. [10]

Localization may be misleading in cases of referred pain. Referred pain typically originates from a noxious stimulus to nociceptors of visceral organs. It may be perceived in anatomical locations remote from the site of pathology. [6] Referral patterns are theorized to be due to the spinal convergence of visceral and somatic afferent fibers on spinothalamic neurons.

Duration

In general, the chronicity of pain can help determine the urgency of a patient presenting with pain. A patient with many years of non-progressive low back pain is not likely to acutely deteriorate. However, chronicity does not necessarily indicate a benign situation. The physician should be aware of changes in pain, pains in new locations, or other more ominous changes in function (eg, bladder incontinence in a patient with chronic low back pain). [10]

There is no consensus on a specific time period that defines acute pain versus chronic pain. Most clinicians and researchers use durations of either 3 months, 6 months, or (less frequently) 12 months to distinguish between acute and chronic pain.

Pain is said to be acute when presented within the first 3–6 months from time of onset. Acute pain typically has an abrupt start with identifiable associated events, although this may not be the case. It also may resolve within the first 6 months without intervention.  Chronic pain does not resolve within 3–6 months of its initiation and progresses beyond 6 months of duration. 

Course

The evolution of pain over the time from onset may be worsening, improving, or static. The evolution of pain location or character may aid in diagnosis. Acute or abrupt increases in pain intensity or changes in location should raise red flags.

The tempo may be described as constant or intermittent. The tempo and frequency can help differentiate the diagnosis. The timing of pain may also provide clues. Symptoms may be most severe in the morning upon waking, later in the day, or during the night, depending on the etiology of the pain. Paroxysmal and intermittent pains can be difficult to characterize, and pain dairies may provide benefit in these cases. [9]

Character and quality of pain

The quality of pain is described in a purely subjective manner. Describing the character of pain is often difficult, especially if it is a new or unique sensation that has never been experienced by the patient. There are many words in the English language to describe pain and these have been subdivided to classify the nature of the pain. 

Pain that is a result of stimulation of nociceptors is usually described with thermal (eg, hot, cold), mechanical (eg, crushing, tearing), or chemical (eg, iodine in a fresh wound, chili powder in the eyes) characteristics. Nociceptive visceral pain may be described as cramping. [11]

Neuropathic pain is often characterized as burning, tingling, electrical, stabbing, or “pins and needles." Neuralgia pain is often described as lancinating and occurs along the distribution of a single nerve (trigeminal) or nerves. [6]

Aggravating/provoking factors

Various stimuli may exacerbate pain, and determining these factors can aid in establishing the pathophysiologic mechanisms of the pain. Mechanical, environmental, metabolic, or psychological factors may all exacerbate pain. Nociceptive pain can typically be amplified by certain body positions and/or activities.

Fear of movement or re-injury is concerning as it can be associated with chronicity. It is not uncommon to develop antalgic gait or positions in patients who deal with chronic pain. Furthermore, undertreated pain may lead to avoidance of movement, which in turn may cause muscle contractures and adhesive capsulitis.

Alleviating factors

Factors that relieve pain should be assessed not only to aid in diagnosis, but also with determining what has been attempted and what helps or does not help with their pain. Determining how the patient alleviates pain may also assess for healthy coping behaviors. Alleviating factors may include mechanical (eg, certain positions, activity modifications), thermal, pharmacological, environmental, psychological, medications, or other treatment interventions. It is important to assess treatments that have been tried and are continually used, because in some circumstances, they may actually be exacerbating or propagating the pain.  

Associated symptoms

Many other symptoms and systems can be reviewed to help narrow a diagnosis or rule out more concerning pathology or systemic disease.  Associated signs may be localized to the painful area, such as with inflammation producing erythema, warmth, or local edema. Sympathetically mediated pain can be accompanied by evidence of edema, vascular changes, abnormal sweating, allodynia, hyperalgesia, or hyperpathia. [6] Certain mechanical symptoms, such as joint-locking, giving-way, popping, catching, or clicking should be documented. Preceding symptoms or aura should be assessed. 

Potential signs of severe neurologic injuries could include weakness, other sensory disturbances, bowel and/or bladder changes. Unexpected weight loss, fevers, or rashes may be clues for a more concerning underlying diagnosis. Nociceptive visceral pain may be associated with autonomic hyperactivity or gastrointestinal complaints. [6]

Severity of pain

Pain is subjective expression. Objective quantification of pain has been one of the greatest challenges physicians have faced in modern medicine. There is obvious and great variability in the severity of pain among seemingly similar cohort groups. Pain may be expressed both verbally and nonverbally through facial expression, body movements, and other physiologic signs.

Severity of pain may include the intensity graded by the patient or the impact pain has on function. Intensity may be assessed with certain scales that will be reviewed below. The impact on function may include changes with activities of daily living, activity level, and work-related duties. Pain may have an impact on sleep, mood, appetite, or social relationships.

Barriers to pain assessment

Barriers to pain assessment occur because of the assessment’s significant reliance on the ability to communicate subjective complaints. Pain assessment becomes even more complicated and difficult in patients who are nonverbal or have communication difficulties.

Pain threshold is also an issue. There are two thresholds in terms of pain: the perception threshold and the tolerance threshold. The pain perception threshold is the point at which the stimulus begins to hurt, and the pain tolerance threshold is reached when the subject acts to stop the pain. The variability of pain threshold is apparent not only in individual basis within one community, but it is also apparent between patients of different sex, ethnicity, and race.

Another challenge in pain management is recognizing patients who are exaggerating symptoms for secondary gains, including patients who abuse prescription opioids. [12]

Pain Scales

Pain measurement tools may be categorized as either single-dimensional or multidimensional scales. The measures require patient self-report on an aspect or aspects of the pain. The results must be viewed as guides and not absolutes. They should be viewed as only adjuncts to the history and physical examination of the patient. [3]

Single-dimensional scales

Single-dimensional scales are a simple way for patients to rate one aspect, typically intensity, of their pain. These scales may be useful in acute pain when the etiology is clear, such as trauma, pancreatitis, and otitis media. [3, 6] However, they can oversimplify the pain experience and results vary between certain patient populations and different diagnoses. [13] The three most commonly utilized tools to quantify pain intensity include verbal rating scales, numeric rating scales, and visual analogue scales. [5]

Verbal Rating Scales (Verbal Descriptor Scales) utilize common words (eg, mild, severe) to grade pain intensity. [3, 6] The Melzack and Torgerson scale uses five verbal descriptors: mild, discomforting, distressing, horrible, and excruciating. [14]

Numeric Rating Scales are common and simple. Patients may be asked to circle numbers equally spaced on a page or verbally rate pain intensity using a scale of 0–10, in which 0 represents “no pain” and 10 represents “the worst pain imaginable.” Advantages of numeric scales are their simplicity, reproducibility, and sensitivity to small changes in pain. Children that are able to count and have a concept of numbers may use this scale. [3, 6]

The Visual Analog Scale is similar to the numeric rating scale, except that the patient marks on a measured line, in which one end represents “no pain” and the other end represents “the worst pain imaginable.” [3, 6] Other visual tools may use pictures of the human body for the patient to mark the location of pain.

The Wong–Baker Faces Pain Rating Scale can be used with children, adults, patients with mild to moderate cognitive impairment, and patients with language issues. This scale presents pictures of 6–8 different facial expressions that show a range of emotions, as shown in the image below. [6]

Faces Pain Rating Scale. Faces Pain Rating Scale.

Multidimensional scales

Multidimensional scales are more complex and time consuming, but may measure the intensity, nature, and location of the pain, and impact the pain is having on activity or mood. These are useful in complex or persistent acute or chronic pain cases when intensity needs to be assessed as well as social support, interference with activities of daily living, and depression.

The McGill Pain Questionnaire provides quantitative measurement of pain and can discriminate between sensory and emotional aspects of pain. It can also be beneficial to detect response to treatment. It involves four parts and requires 5–15 minutes to complete. It primarily consists of different adjectives used to describe pain in three dimensions: sensory, affective, and evaluative. The words are subdivided into 20 subclasses that are tiered to represent relative intensity. Distribution, temporal pattern, and intensity of pain are also evaluated. [15]  Two adaptations have been developed: the short-form McGill Pain Questionnaire (SF-MPQ) and the SF-MPQ2; which are shorter, easier to complete and more sensitive to change. [16]

The Brief Pain Inventory quantifies both pain intensity and interference or impact on function. It is used for patients with cancer, human immunodeficiency virus, and arthritis. It takes 5–15 minutes to complete and uses 11 numeric scales to address pain intensity, mood, ability to work, relationships, sleep, enjoyment of life, and the effect of pain on general activity. The Brief Pain Inventory can measure the progress of a patient with a progressive disease and can show improvement or decline in the patient's mood and activity level. Evaluating function is important in overall pain management. [17]

The Memorial Pain Assessment Card is a simple and quick multidimensional pain assessment tool for patients with cancer. It consists of three separate visual analog scales and assesses pain, pain relief, and mood. The card includes a set of adjectives to describe pain intensity and takes very little time to administer. [18]

Pain Assessment in the Elderly

Acute pain and chronic pain are common in the elderly. Pain may be the limiting factor for activities and mobility in the elderly, and effective assessment and management is vital for functional independence. It also may result in decreased morbidity and health care expenditures.

Many factors may act as barriers in the adequate assessment of pain in older patients. Inadequate communication of pain may be one of the greatest impediments. Stoicism, beliefs that pain is an essential part of ageing, and overshadowing multiple medical comorbidities may lead to underreporting of pain.

Pain assessment may also be complicated by decreases in hearing and visual acuity, so tools that require extensive explanation or visualization to perform will be more difficult and possibly less reliable. Cognitive impairment or dementia can also be an impediment to pain assessment. The verbal descriptor scale may be the easiest tool for the elderly with or without cognitive impairment. This measure allows patients to describe what they are feeling with common words rather than having to convert how they feel to a number, facial representation, or a point somewhere on a straight line. 

In those with severe cognitive impairment or inability to self-report pain, the Pain Assessment in Advanced Dementia (PAINAD) scale can be used. This scale utilizes observed pain behaviors to determine the level of pain, is easy to use and sensitive, but has a high false positive rate.

An important factor in pain assessment in the elderly is assessing the effect the pain is having on their lives, rather than the intensity of the pain itself. Necessary activities of daily living are often maintained despite severe pain. However, the effect pain has on elective activities, such as social functions or advanced activities of daily living may correlate with severity of pain. With impaired cognitive ability, any baseline impairment in activity may also worsen with significant pain. [19, 20]

Pain Assessment in Infants

Infants are dependent on their caregivers to assess their pain and to determine the effectiveness of management efforts because they cannot verbalize their pain sensations. Facial activity, crying, and body movements are the most studied behavioral responses to pain in neonates. A limited number of facial actions have been studied in infants. The most obvious index is an infant's cry; however, the interpretation is difficult.

Two tools use a combination of behavioral and physiological measurement. CRIES (ie, crying, requires oxygen, increased vital signs, expression, sleeplessness) uses the five variables on a 0–2 point scale to assess neonatal postoperative pain. [1] The Modified Behavioral Pain Scale uses three factors (facial expression, cry, and movements) and has been validated for 2- to 6-month-old children. [2]

Pain Assessment in Young Children

In children, the caregiver must be aware of the developmental stage of the child to best determine the assessment tool. It is important to interpret behavioral observations cautiously and with cultural sensitivity. Limited cognitive or language skills may influence pain measures, as well as the positive or negative consequences a child’s pain reports or behaviors produce. A child sleeping more than usual, for example, may actually be in significant pain without any crying or whimpering.

In children older than 3–4 years, self-report measures may be used. However, children may underreport their pain to avoid future injections or other procedures aimed at alleviating the pain.

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