Which should be included when assessing pain?

Summary and Recommendations

Pain assessment is a critical step in the process of pain management. Any study of pain should include at least one self-report measure, and it is often beneficial to use either multiple measures or a multidimensional measure of pain (e.g., the short form of the MPQ, which includes both verbal descriptors and a VAS). A review of the extensive cancer pain literature indicated that single-item VAS, VRS, and NRS all showed good validity and reliability, and it was concluded that no one of these measures was consistently superior. However, we can advise that in studies of elderly or cognitively compromised subjects, use of a VRS or NRS is strongly preferable to use of a VAS. Pain relief should be measured using sequential ratings (i.e., changes from pretreatment to posttreatment), rather than a retrospective impression. Electronic assessment and daily diaries may be extremely useful in reducing the memory biases associated with recall of pain, and in obtaining a more precise sense of the variability in day-to-day pain symptoms. Behavioral observation and experimental pain assessment are all useful and potentially informative adjunctive measures of pain responses, but none can substitute for self-report of the pain experience. The one exception to this standard is infants, in whom coding of behavioral or facial responses is the current gold standard for pain assessment. For slightly older children, a pictorial scale such as the FACES Scale or Oucher Scale may be used, whereas in children who are 6 years or older, a standard VAS may be the optimal choice. Finally, substantial research suggests that health care professionals, no matter how expert, are not reliable judges of patients’ report of pain. Their estimates are both inaccurate and systematically biased in the direction of underestimation. In this chapter, we have attempted to provide those with an interest in treating or studying pain with some of the requisite information on which to base choices regarding pain assessment. Measures should be selected with as complete knowledge as possible of their properties, strengths, and limitations.

Rating Scales

Many rating scales have been suggested in the literature to measure the intensity of a patient’s pain.51,68 These rating scales are relatively quick and easy to administer. They can be presented in a verbal or visual format. Rating scales can be used as part of the initial assessment of pain as well as before, during, or after subsequent treatment sessions or procedures. However, when the dominant driver of the individual’s pain experience is nociplastic in nature, constant cues from clinicians for pain attention may facilitate the maintenance of pain hypervigilance and communicate the message that the pain output is important or should be strongly monitored (which may not be the case in individuals with nociplastic-dominant pain). Facilitating pain hypervigilance may hinder rehabilitation progress and only help to maintain the abnormal processing of stimuli within the nervous system.

The information obtained from the rating scales has been criticized as being one dimensional51 and not providing a true representation of the individual’s total pain experience. The information gained from therating scales is momentary and therefore may provide the clinician with limited information regarding the effectiveness of an applied intervention in short- and long-term variations or changes in pain intensity. To administer a numerical pain rating scale (NPRS), the therapist generally asks the patient to assign a number to his or her pain intensity or to “rate the pain” on a scale of 0 to 10, with 0 referring to no pain, and 10 being the worst pain imaginable. The visual analog scale (VAS) has several modifications (Fig. 94.6). Commonly, it includes a 10-cm horizontal or vertical line that represents a range of pain intensity. The line may have no marks or descriptive words except at the ends of the line, which represent no pain at one end and the worst pain imaginable at the opposite end. Other visual scales may place more word descriptors along the continuum. The patient places a mark on the line to indicate her or his level of pain. A problem that may occur when using the rating scales is that the patient may initially start on the scale near or at the end of the scale, indicating the worst pain, and then the patient’s pain experience becomes worse. In this case, the patient’s response on the scale may exceed the upper limit. Additionally, patients often rate their pain on what they perceive as an average pain scale for other people, giving a much higher rating. In this case, the clinician may ask the patient to rate on her or his own 0 to 10 scale without thinking of other people’s experiences.

Using rating scales, clinicians can garner information regarding the individual’s pain at worst, pain at best, and pain on average over a given period (days, weeks, months). This scale can also be used to determine pain with specific activities, which may aide clinicians in identifying pain threshold or pain tolerance of the individual. Pain threshold is defined as the minimum stimulus intensity that results in pain. Pain threshold is highly reproducible in different individuals within clinical pain experiments and in the same individual at different time periods. Conversely, pain tolerance is highly variable and correlates well with the affective and cognitive components of pain. Tolerance implies a question about how much pain an individual is willing to accept in a given situation.1 Pain tolerance may be affected by fatigue, lack of control, stress, environment, and anxiety. During examination, therapists should determine whether any of the variables that modulate pain tolerance are present.

The elderly

The past several decades have witnessed a steady increase in research related to pain in the elderly. Most pain assessment tools that have been validated in middle-aged adults have also been psychometrically examined in older subjects. In general, this body of research indicates that increasing age is associated with a higher frequency of incomplete or nonscorable responses on a VAS, but not on a VRS or NRS. Across studies, VAS failure rates in cognitively intact elderly samples range from 7% to 30% of respondents, with the percentages increasing substantially (up to 73%) in cognitively impaired samples.6 Studies of preferences indicate that, in general, a VAS is rated as one of the least preferred measures among the elderly while a VRS often receives the highest preference scores. In addition, it has been suggested that the MPQ (long form) is inappropriate for use in elderly samples due to its complexity and time requirements. Although research does not support the contention that the elderly make more errors on the MPQ, several studies have now shown that older adults report less pain on the MPQ (i.e., choose fewer words) even when NRS- or VRS-rated pain does not differ.41,42 These findings may suggest that the MPQ assesses the construct of pain differently across age-groups, and caution may be warranted before using this instrument with older samples.

Collectively, recent finding suggest that a VRS produces the fewest “failure” responses among samples of cognitively intact and cognitively impaired elderly subjects while a VAS produces the largest number. It is therefore recommended that studies of pain in the elderly use, at minimum, a VRS to assess pain intensity. Moreover, some research suggest that the use of behavioral pain indicators may be preferable as among individuals with cognitive impairments, as these patients tend to underreport pain intensity on standard self-report measures, but show preserved indices of pain behaviors.43,44

Evaluation of Muscle Discomfort

The basis for the classification of disorders underlying muscle discomfort can be anatomical, temporal in relation to exercise, muscle pathology, and the presence or absence of active muscle contraction during the discomfort (Pestronk, 2019). Evaluation of muscle discomfort typically begins with a history that includes the type, localization, inducing factors, and evolution of the pain; drug use; and mood disorders. The physical examination requires special attention to the localization of any tenderness or weakness. The pain may produce the appearance of weakness by preventing full effort. Typical of this type of “weakness” on examination is sudden reduction in the apparent level of effort, rather than smooth movement through the range of motion expected with true muscle weakness. The sensory examination is important because small-fiber neuropathies commonly cause discomfort with apparent localization in muscle. A general examination is needed to evaluate the possibility that pain may be arising from other tissues such as joints. Blood studies may include creatine kinase (CK), aldolase, complete blood cell count, sedimentation rate, potassium, magnesium, calcium, phosphate, lactate, thyroid functions, and evaluation for systemic immune disorders. CK values of African Americans are higher than those of other races (up to 3 times higher than Caucasian Americans) (Kenney et al., 2012). Evaluate urine myoglobin in patients with a high CK and severe myalgias, especially when they relate to exercise. Electromyography (EMG) may suggest myopathy or if normal may indicate that muscle pain is arising from anatomical loci other than muscle. Nerve conduction studies may detect an underlying neuropathy, but objective documentation of small-fiber neuropathies can require quantitative sensory testing or skin biopsy with staining of intraepidermal nerves. There is reduced innervation of blood vessels within muscle in patients with small-fiber neuropathy (seeFig. 29.1,B–E) (Dori et al., 2015).

Magnetic resonance imaging (MRI) could show increased muscle signal on short tau inversion recovery (STIR) sequences. Muscle ultrasound can be a useful and noninvasive method of localizing and defining types of muscle pathology. Muscle biopsy is most often useful in the presence of another abnormal test result such as a high serum CK, aldolase, lactate, or an abnormal EMG. However, important clues to treatable disorders such as fasciitis or systemic immune disorders (connective tissue pathology, perivascular inflammation, or granulomas) may be present in muscle in the absence of other positive testing. Examination of both muscle and connective tissue increases the yield of muscle biopsy in syndromes with muscle discomfort. There is increased diagnostic yield from muscle biopsies if in addition to routine morphological analysis and processing, histochemical analysis includes staining for acid phosphatase, alkaline phosphatase, esterase, mitochondrial enzymes, glycolytic enzymes, C5b-9 complement, and major histocompatibility complex (MHC) class I. While disorders of glycogen and lipid metabolism often result in abnormal muscle histochemistry, deficiencies in some enzymes (e.g., phosphoglycerate kinase or carnitine palmitoyltransferase [CPT] II deficiencies) may not cause muscle pathology and diagnosis is best made by genetic testing. Ultrastructural examination of muscle rarely provides additional information in muscle pain syndromes.

Pain Assessment

Inadequate pain assessment is a major factor in the undermedication of pain. In a study of cancer pain management strategies (358), 76% of physicians reported having problems with pain assessment. The use of standardized pain assessment measures and sensitive, systematic clinical interviews, lead to improvement in both pain assessment and treatment. Awareness of the myths about pain and analgesia can be helpful in overcoming barriers that hinder the assessment process. Common myths that interfere with pain assessment include:

Patients often exaggerate their complaints of pain.

Latino-Americans and African-Americans exaggerate their complaints of pain and therefore need less analgesia.

Patients with present or past history of addiction lie about pain as part of their drug-seeking behavior.

The etiology of pain is often psychogenic.

The etiology of pain most often remains obscure.

One common misconception is that patients tend to exaggerate their complaints of pain. Research studies of patient-controlled analgesia (PCA) (359,360) show that patients tend to avoid the prospect of the complete disappearance of pain. Patients' need to “preserve a modicum of pain” (361) can be understood psychodynamically as a way to maintain a sense of the self that is separate from the environment and to protect the self against the prospects of existential disintegration. Patient stoicism or need to maintain the same level of pain, at a more conscious level, could be a way to avoid excessive sedation or the other side effects of analgesia or the fear of becoming addicted to narcotics. Since patients are generally reluctant to volunteer their complaints of pain (358), physicians need to assess for pain on a routine basis. A clinical interview can be helpful in determining the cause of pain. Patients with intact cognitive function can translate pain perceptions into verbal communication. The vocabulary used to describe nociceptive pain differs from that for neuropathic pain. Table 19.25 highlights this distinction.

TABLE 19.25. Description of pain and etiology

Nociceptive painNeuropathic painSorenessUnfamiliar sensations (dysesthesias)AchingNumbnessStabbingTinglingSharpElectricalDullPins and needles (paresthesias)

Throbbing

Crushing

Just as the quality of pain is helpful in determining its etiology, so is the location of the pain. Pain can be focal or referred. Referred pain can follow a dermatomal distribution, as does postherpetic pain. Many physicians rely on non-verbal expressions of pain more than what the patient communicates verbally. Non-verbal cues include crying, moaning, yelling, grimacing, splinting, rubbing, insomnia, anergia, anorexia, apathy, anxious mood, dysphoric mood, hypertension, tachycardia, and diaphoresis. While non-verbal signs may be useful in persons with dementia, delirium, depression, or aphasia, they should not be necessary to validate or supersede verbal complaints of pain. Cancer pain research indicates (331,362) that non-verbal cues are no more accurate than and are no substitute for a patient's verbal report of pain.

Pain-assessment scales can be used both for research purposes and to enhance the clinical pain interview. They are particularly useful in persons with HIV dementia, who may have difficulty describing the intensity, location, or chronology of acute or chronic pain (363). The Wisconsin Brief Pain Inventory (BPI) has been used in clinical research for persons with cancer and AIDS (340,364,365). It helps to determine localization and intensity of pain. It also measures adequacy of analgesia and the impact of pain on quality-of-life issues such as activity, mood, ambulation, work, relationship, sleep, and enjoyment.

Pain Measurement

Pain assessment is difficult in infants and children, but regular assessment of the existence and severity of pain and the child's response to treatment15 are essential for pediatric pain management. Pain can be assessed by psychological methods, physiological measures, or behavioral observation, depending on the age of the child and his or her ability to communicate. Acceptable postoperative pain assessment requires consideration of the complexity of children's pain perception and psychological as well as developmental factors. Age-appropriate pain assessment is essential for managing pediatric patients with pain. Both subjective and objective assessment tools may be used, depending on the patient's age and clinical status.

Because pain is a subjective experience, individual self-report is often preferred. Children between the ages of 3 and 7 years are competent to provide information regarding the location, quality, intensity, and tolerability of pain. Observation of behavior should be used to complement self-report and can be an acceptable alternative when valid self-report is not available. The pain assessment tools should be introduced before the operation or before the pain occurs. Each institution must adapt a uniform tool for pain assessment in pediatric patients.

The six-face Faces Pain Scale–Revised is useful in the assessment of acute pain intensity in children 4 years and older. It has the advantage of being suitable for use with the most widely applied metric scoring system (0–10) and conforms closely to a linear interval scale.16 In a study of 276 children, Baxt et al17 demonstrated the feasibility of assessing pain after pediatric injury with the use of two validated scales, the Bieri Faces Pain Scale and the Color Analogue Scale. They also established the worth of parental reports of pain when the child is not able to provide a self-report.17

Pain assessment at home is an especially difficult task for parents postoperatively. The findings of Chambers et al18 supported the reliability and validity of the 15-item Parents' Postoperative Pain Measure (PPPM) as a measurement of postoperative pain among children ages 2 to 12 years. Koh et al19 compared 152 children with cognitive impairment and 138 nonimpaired children. They showed that children with cognitive impairment who underwent surgery received less opioid in the perioperative period than children without cognitive impairment. The Face, Legs, Activity, Cry, Consolability (FLACC) pain assessment tool may facilitate reliable and valid observational pain assessment in children with cognitive impairment.20

Pain.

Pain assessment can indicate the cause and extent of a wound and the appropriate pain management approaches. The nature, onset, duration, and exacerbating and relieving factors, as well as pain severity, are aspects of pain to be considered in making the diagnosis. Pain caused by hypoxia or ischemia, which is usually deep and cramping in quality, and pain that results from neuropathy, which is usually burning, lancinating, or electric-like,86 are discussed in Chapters 29 and 30, respectively. Throbbing, localized pain, termed nociceptive, is often experienced with infection. Deep pain that increases with pressure may indicate the presence of osteomyelitis.87 Superficial tenderness or burning can occur with exposed nerve endings, may be accompanied by sharp shooting pains, and can make sharp debridement difficult for the patient to tolerate. Pain when red striated tissue is pinched with forceps indicates the tissue is viable muscle and should not be debrided. Pain severity can be assessed using a variety of scales as described in Chapter 22.

A study of patients with PUs found that 100% of the patients reported pain related to the ulcer with a mean intensity of 5.80/10 (±2.93). The verbal descriptors (from the McGill Pain Questionnaire) used most frequently to describe the pain were throbbing, sharp, burning, aching, and tugging.88

Although the best pain assessment tool for patients with chronic wounds has yet to be identified, the literature consistently supports the need for measuring pain and using this information to guide the treatment of patients with acute and chronic wounds.

Pain

Pain assessment is the primary outcome measure in acute gout RCTs. However, pain is also a common symptom of chronic moderate-to-severe gout. Pain was assessed on a 0-to-100 visual analog scale in the pegloticase RCTs.15 In these studies, treatment with pegloticase was associated with statistical improvement in pain scores compared to the placebo group. In addition, SF-36 bodily pain scale has been assessed recently in an observational study.4 SF-36 bodily pain scale was able to discriminate patients with versus without palpable tophi, monoarticular/oligoarticular versus polyarticular joint involvement, and absence versus presence of radiographic damage. In addition, chronic treatment with urate-lowering therapy and colchicine was associated with significant improvement in bodily pain at 1 year with large effect sizes (1.09).

Pain

Pain assessment in the cancer patient requires understanding of the relationships among pain, nociception, and suffering. Nociception refers to the activity in the afferent nervous system induced by potentially tissue-damaging stimuli. A comprehensive assessment will identify a nociception lesion in most patients with cancer pain. Pain is the perception of nociception. It is strongly influenced by affective and cognitive processes unique to the individual. These processes may eventuate in an intensity of pain that is either greater or less than that anticipated by the degree of tissue damage. Suffering is a construct that refers to a more global response, which is related to unrelieved symptoms (including pain) and many perceived losses, including those related to evolving disability, social isolation, financial concerns, loss of role in the family, and fear of death. It is important for the clinician to recognize that suffering may occur in the absence of active nociception.

Clinical interventions targeted solely at the complaint of pain—particularly at the nociceptive component—are unlikely to measurably benefit patients whose complaints are an expression of a more global degree of suffering. Indeed, such treatment plans are often perceived by patient and family as uncompassionate.

What are the five key components of pain assessment?

When assessing pain What four factors should be noted and documented?

What is the most important part of a pain assessment?

What is the first step in assessing pain?