Pain is one of the most prevalent, misunderstood, and complex issues in health care and a leading reason Americans seek health care. In 2017, pain accounted for more than 22 million visits to U.S. EDs.1 A 2016 systematic review of studies published between 1990 and 2013, which examined the prevalence of pain in hospitalized adult patients, found that hospital-wide pain prevalence ranged from 37.7% to 84% and severe pain prevalence ranged from 9% to 36%.2 Pain prevalence was higher among surgical patients than medical patients, though up to 55% of medical patients reported pain. Data collected in the 2010 National Hospital Ambulatory Medical Care Survey indicate that an estimated 48.3 million ambulatory surgery procedures were performed that year in hospitals (25.7 million) and ambulatory surgery centers (22.5 million),3 suggesting that postsurgical pain is a likely source of the prevalent acute pain reported by hospitalized patients.

A National Pain Strategy. Over a decade ago, the Institute of Medicine (now the National Academy of Medicine) proclaimed the need to revolutionize how health care professionals, researchers, and the public understand and treat pain.4 This spotlight on a major public health problem led the U.S. Department of Health and Human Services to develop a National Pain Strategy to prevent the progression of acute to chronic pain and the development of high-impact chronic pain, which is characterized by pain-related functional decline and physical disability that limits participation in work, social, and self-care activities for six months or longer.5

The problem with one-dimensional pain-rating scales. A cross-sectional study by van Boekel and colleagues of patients who underwent major surgery between January 2008 and August 2013 found that a one-dimensional numeric rating scale (NRS) reflected little about the tolerability of postoperative pain.6 In this study, a low NRS score did not indicate that patients found postoperative pain acceptable. Nor did a high NRS score invariably indicate patient dissatisfaction with pain levels. Investigators compared four distinct measures of pain: movement-evoked pain (MEP) reported by patients on a 10-point NRS (NRS-MEP), patient opinion on the acceptability of pain, nurse observation of patient performance of recovery-promoting activities, and a combination of patient opinion on the acceptability of pain and nurse observation of the clinical desirability of patient performance of activities.6

Focusing solely on pain intensity as the primary metric for treatment is not only insufficient but detrimental, as it can contribute to opioid overprescribing and overuse, thereby putting patients at risk for oversedation and respiratory depression.7 Many scales used by patients to self-report their pain, such as numeric, visual analog, and verbal descriptor scales, are one dimensional, designed to assess only pain intensity,8 the perception of which varies widely among patients and within individuals over time, with recovery, and with various activities.

In the study by van Boekel and colleagues, approximately one of 10 patients who reported a low NRS-MEP score of 0 to 4 considered their pain unacceptable, and one in five patients who reported a relatively high NRS-MEP score of 7 was willing to perform the required physical activities.6 The researchers suggest that NRS scores should be interpreted individually, after observing patients and communicating with them about their pain.6 Such MEP assessments can help clinicians identify patients who have clinically significant pain and are at risk for poor functioning.

This article discusses the importance of assessing MEP; how MEP differs from other types of pain; and what a MEP assessment can reveal about the intensity, impact on patient functioning, and tolerability of pain.

THE MULTIFACETED PAIN ASSESSMENT

Limiting the negative outcomes associated with the progression of acute pain requires a thorough understanding of a patient's pain, which can be acquired only through a detailed, multifaceted pain assessment.6, 9 Assessments should not be limited to inpatient care but should also be performed in outpatient and ambulatory care settings where acute postoperative pain may be treated.

First, it is appropriate and essential to establish if pain is present. Then it is important to establish the following characteristics of the patient's pain:

* quality

* intensity

* location(s) during the movement activity

* duration

* patient's opinion about acceptability of the pain and ability to make appropriate movements

* alleviating and exacerbating factors

* objective impact on function and physical activity

UNDERSTANDING MEP AND ITS ASSESSMENT

MEP is any pain that is associated with active or passive movement of an involved area and is distinct from any ongoing pain.10, 11 Unlike pain at rest, breakthrough pain, pain flares, or pain crises, MEP can be traced consistently to changes or increases in movement, mobility, physical activity, or position.11 The health care literature variously describes MEP using terms like movement-induced, -exacerbated, -related, -provoked, or -associated pain, and pain-on-movement.11

MEP assessment is a specific approach that measures pain during movement to more accurately reflect pain's intensity, impact on function, and tolerability. Unlike pain assessments that ask patients to report on pain at rest or to recall pain they experienced with prior movement, MEP assessments allow patients to provide a "real-time" report of symptoms that occur with movement12 and afford clinicians an opportunity to observe such signs as an impaired gait, reduced range of motion, or physical adaptations that may indicate the pain is affecting patient functioning (see Figure 1). This type of assessment is often likened to point-of-care testing because it allows real-time reporting of symptoms.

Figure 1. A depiction of a pain assessment continuum from use of pain recall questionnaires, which capture past pain at rest (and inadvertently some movement-related pain), to spontaneous pain assessment, which captures present pain but not pain related to physical activity. Standardized methods for assessing present movement-evoked pain are needed. Reprinted with permission from Corbett DB, et al. Movement-evoked pain: transforming the way we understand and measure pain.

Assessing and reporting on both MEP and pain at rest can help clinicians determine whether pain is

* not well controlled.

* transitioning to chronic pain.

* to be expected after a painful procedure or injury.

* a reflection of fear, anxiety, or another psychosocial factor that demands attention to reduce its influence on physical functioning.

Assessments of dynamic pain-pain that occurs with movement, deep breathing, or coughing-conducted during prescribed or permitted activities are necessary to fully understand the impact of pain on the patient. Acute postoperative pain that is well controlled at rest may be significantly exacerbated by movement.13 A systematic review of MEP versus pain at rest in postsurgical clinical trials and meta-analyses found that MEP was 101% more intense than pain at rest in the first 24 hours after surgery and was 226% and 209% more intense than pain at rest at 48 and 72 hours, respectively.14 Nevertheless, assessment of dynamic pain is rarely performed or, if performed, is rarely documented as distinct from pain the patient experiences at rest.14

While assessing and treating pain at rest is important in supporting patients' comfort while in bed, assessing dynamic pain is often more important in reducing risks of cardiopulmonary complications, postsurgical thromboembolism, and progression from acute to chronic hyperalgesic pain.15 In addition, assessing and addressing dynamic pain can reduce immobility, a known risk factor for chronic hyperalgesic postsurgical pain, and can reveal potency differences between analgesic approaches, such as thoracic epidural, lumbar epidural, and patient-controlled analgesia.15 Given the importance of assessing function and pain during movement, Booker and colleagues advocated dynamic pain assessments, noting that traditional, one-dimensional assessments of pain at rest provide little or no information on the characteristics and triggers of pain, such as movement or immobility, and their impact on function.12 The implications for pain control are enormous, because MEP is particularly prevalent and disabling in patients with acute postoperative pain.

ACUTE POSTOPERATIVE PAIN

High-intensity acute postoperative pain impedes functioning and surgical recovery, and reduces quality of life while increasing hospital length of stay, medical costs, and duration of opioid use.16 Acute postoperative pain also increases morbidity, possibly precipitating the development of chronic postsurgical pain.17, 18

An observational study of the relationship between acute postoperative pain and complications within 30 days of surgery found that both high acute postoperative NRS-MEP scores and the pain patients considered unacceptable on postoperative day 1 were associated with a greater number of postoperative complications.19 The association between early postoperative pain and complications may be explained in part by the fact that postsurgical pain impedes both postsurgical mobilization and coughing, thus increasing the risk of respiratory complications.19 Impediments to early mobilization after surgery and effective pain control in the perioperative setting are more expediently identified by assessing MEP and can help to prevent morbidity, such as pulmonary complications and pneumonia attributed to severe pain.

PREOPERATIVE PAIN AS A PREDICTOR OF POSTOPERATIVE PAIN

Preoperative assessments of pain during movement can help clinicians identify patients at elevated risk for higher levels of postoperative MEP, complications, and self-care deficits, as well as patients who will require opioids or opioid-sparing and opioid-free analgesic strategies in the perioperative period.20, 21

In a seminal nursing study of acute pain after total knee replacement, patients with preoperative MEP were found to be 20 times more likely to experience severe postoperative MEP.22 More recently, an international multicenter database analysis of risk factors for poor postoperative acute pain outcomes in more than 50,000 adult patients indicated that patients with three or more of the following four preoperative risk factors: age, female sex, preoperative opioid intake, and preoperative chronic pain were at higher risk for poor postoperative pain control.23

Observing, documenting, and communicating patterns of a patient's preoperative MEP can help establish baseline and maximum pain intensity. Postoperative assessment of MEP can then reveal how the surgical procedure changes the characteristics or intensity of pain with movement. In a prospective study of the intensity of postoperative pain after cardiac surgery, investigators found that pain was moderate during rest and during activities two days following surgery but began to decrease on day 3 for activities other than coughing, for which pain intensity declined on postoperative day 6.24

The range of preoperative pain from baseline to maximum (ceiling) intensity can be used to

* guide postoperative care.

* safely mobilize the patient.

* set goals for maintaining pain within an acceptable range.

CLINICAL INTEGRATION

MEP as an assessment and outcome in postoperative drug efficacy trials has been used and recommended for nearly 30 years.25 To integrate MEP assessment into practice, the following assumptions need to be challenged. First, that assessing pain at rest is adequate to formulate an effective care plan. Some patients may stop all movement when in pain, while others may push through the pain. Both extremes carry risks of harm. Second, that assessing pain with movement may aggravate existing chronic pain, precluding the possibility of controlling acute pain. Immobility is known to worsen both pain and mobility. Finally, that pain with movement signals the need to avoid all activity, an idea that contributes to a fear-avoidance pattern that can result in poor outcomes. For example, in a small study (N = 26), MEP during coughing and walking after abdominal surgery and patients' fear of wound dehiscence were significantly correlated with lower cough peak expiratory flow.26 To this point, nurses should always consider ethical principles and follow institutional policy to determine when a MEP assessment will be meaningful for patient care and optimal recovery, since such an assessment may cause transient pain, discomfort, or distress.12

HOW TO CONDUCT A MEP ASSESSMENT

Pain screening. Given the variability in the verbal, emotional, and behavioral expression of pain, it is important to screen for the presence of pain with a simple question such as, "Are you having any pain or discomfort now?" If the patient's response is affirmative, further assessment is warranted; if negative, a multidimensional assessment can be delayed until pain is reported or treatment is needed. When a patient requests medication or demonstrates nonverbal expressions of pain such as facial cues, vocalizations, or slow and guarded positional changes or movements, a more in-depth assessment involving formal observation and assessment of MEP is justified.

Pain assessment with observation. The Centers for Medicare and Medicaid Services (CMS) has concluded that observational pain assessments during movement-based activities are more likely to reveal underlying pain than assessments conducted at rest.27 While MEP assessment is not a substitute for a patient's freely offered self-report of pain, astute observations by the health care provider can enhance rather than discredit the patient's self-report. Together, the subjective measure (the patient's self-report) and the objective measure (the nurse's observation of patient function) provide a fuller understanding of the experience of pain and may help to identify other psychosocial factors that require attention. There are two approaches to observing the presence of pain and the impact of movement on pain: natural observation and evoked observation.11

Natural observation. Observation of naturally occurring, probable, predictable pain involves observing and asking the patient about the presence, intensity, and impact of pain during routine physical activities, such as turning, changing position, walking, bathing, and dressing.12 This approach adds no time to nurses' normal workflow because it can be accomplished during routine care tasks. It's important to note whether the patient makes adaptations in performing an activity or avoids certain movements in order to prevent or reduce pain. Observation of such activities is key to understanding a patient's estimation of pain and interpreting the impact of the pain on patient function.12, 28

Evoked observation. Observation of evoked pain involves asking the patient to perform a relevant movement-related task associated with the condition of interest.12 For example, a patient with postoperative bowel resection may be asked to take a deep breath and cough.29 Another example of MEP assessment may involve asking a patient with a successful total knee arthroplasty to flex within a given range of motion or move from supine to sitting or from sitting to standing following herniorrhaphy.30 While these brief protocols may induce some pain, the information they provide is important for understanding factors that may exacerbate pain or serve as barriers to an expedient and full recovery. The patient should be instructed that the risk of transient pain during the movements is outweighed by the recovery benefits and the avoidance of serious complications.12 Offer reassurance that pain relief interventions should offset the fear-avoidance pattern that commonly immobilizes patients and worsens or prolongs their pain and disability. (See Table 16, 31-33 for one example of a MEP assessment protocol.) In lieu of a standardized protocol, using existing validated pain assessment tools is current best practice.12

Table 1. Movement-Evoked Pain (MEP) Assessment Protocol

TOOLS THAT PROMOTE FUNCTION AND HELP CLINICIANS ASSESS MEP

It's important to assess both pain at rest and MEP using validated measures so as to differentiate the two, because a growing body of evidence suggests that they have different underlying mechanisms.34 There are a number of objective tools to measure pain with movement and pain at rest for nonverbal patients with dementia, though more research is necessary to establish validity, reliability, and clinical utility.35, 36

Unfortunately, there are no gold standard objective measures of pain-related functional capacity in verbal postoperative patients.33 Nevertheless, various measures have been developed to quantify treatment-related changes in the physical abilities of individuals with acute pain. Any of the three tools briefly described below can be used to assess MEP while evaluating functional interference (see Table 26, 31-33, 37, 38).

Table 2. Tools That Promote Function and Help Clinicians Assess MEP

The Functional Activity Score (FAS), which is sometimes called the Functional Activity Scale, was developed in Australia. It is a clinically valid tool that is recommended in the recent Acute Pain Management Measurement Toolkit by the Australian and New Zealand College of Anaesthetists and Faculty of Pain Medicine as a standard measure of physical limitations due to postoperative pain.6, 33, 39

The FAS is designed to be used at the bedside. Its three-level ranked categorical score can help nurses assess whether a patient's pain is sufficiently controlled to enable them to undertake appropriate activity given their surgery and premorbid state. A standard procedure-specific protocol should be in place that clearly defines criteria by which to judge a patient's ability to perform physical activities, such as coughing, deep breathing, early movement, and walking on the first three days after surgery, based on whether the FAS shows no, mild, or significant limitation of movement due to pain.

The Johns Hopkins Highest Level of Mobility (JH-HLM) scale is an 8-point ordinal scale that captures mobility milestones and has been tested in a variety of settings with excellent reliability and validity.37 The JH-HLM also has excellent interrater reliability and test-retest reliability for both physical therapists and nurses, as has the Johns Hopkins Activity Measure for Post-Acute Care Inpatient Mobility Short Form, also called "6-Clicks."38 Although the JH-HLM was developed to document mobility unrelated to postoperative pain assessment, it is a useful way to quantify how functional capacity is limited by pain and to communicate it in a way that is clear to the health care team.

Functional Pain Scale (FPS). The FPS was initially developed and validated in community-based older adults and subsequently in hospitalized adults.31, 32 The FPS distinguishes pain that interferes with active versus passive activities (walking versus talking, for example). It also reveals psychosocial factors that may interfere with activities by rating the pain as tolerable or intolerable. Many nurses participating in the validation study indicated that they found the tool fast and easy to incorporate into their workflow.

Critical care tools. For postoperative patients receiving intensive or critical care, established validated pain assessment tools that incorporate movement include the

* Critical-Care Pain Observational Tool and the Behavioral Pain Scale, both developed to assess pain in ICU patients who are unable to self-report.40, 41

* Checklist of Nonverbal Pain Indicators, designed specifically to measure pain behavior in older adults with cognitive impairments.42

Documenting assessment. There are great variations in standardized documentation languages for pain.43 To foster a team-based, patient-centered approach that produces effective treatment plans, institutions should ensure consistency in how pain is assessed, documented, and communicated.44

Documentation should indicate whether pain assessment and subsequent reassessments were completed at rest or during movement. Assessment of movements or activities that induce pain as well as those that promote comfort and restorative functioning should be clearly documented.

Since both the CMS and the Joint Commission acknowledge and advise assessment during movement, health systems should ensure that more specific assessment forms are integrated into electronic health records (EHRs). As technology capabilities advance, point-of-care assessment would most efficiently enable pain assessments to be completed electronically at the bedside, using apps, and both MEP and pain at rest intensity ratings would be immediately transmitted into the EHR workflow, triggering a nursing response. Such technology could improve nurse-patient communication, reporting, and overall satisfaction, with assessment and care responsiveness.

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