1.1 Prevalence of preexisting pain

Estimates of chronic pain range from 20% to 46% in community-dwelling older adults and from 28% to 73% in older adults living in residential care facilities or nursing homes [6]. The prevalence of daily pain tends to increase with age with as many as 75% of adults older than 75 years reporting pain [6, 9]. The prevalence appears to be higher in women [6].

1.2 Recognition

Older adults with cognitive impairment are a specific high-risk group for poor pain control, due both to inadequate recognition and a tendency to undertreatment [6]. Identification of pain is particularly challenging in the perioperative and postoperative period when delirium and medical instability complicate the clinical assessment.

Reasons for underrecognition and undertreatment of pain in older adults include difficulties in assessment, particularly in patients with dementia, fear of side effects and overdose, and general provider uncertainty regarding the response to opioids in a highly complex and comorbid population.

A reluctance to use standing orders for analgesics in hip fracture patients after surgery illustrates this issue [10].

1.3 Negative effects of poor pain control

Regardless of the underlying cause, uncontrolled pain has negative effects on the physiology and clinical outcomes in older adults, especially in the inpatient setting. Pain is a contributor to tachycardia and myocardial oxygen consumption [3]. Poor pain control in hip fracture patients has been shown to lead to increased rates of postoperative delirium, increased length of stay and poor participation in therapy [3]. Uncontrolled pain delays postoperative ambulation and time to recovery. Decreased rates of delirium and early ambulation have been shown to reduce length of stay and postoperative complications including pneumonia [11]. While there is a paucity of evidence about the impact of specific pain regimens on hip fracture outcomes [12], improved pain control is suspected to lead to less morbidity in hip fracture patients postoperatively [10].

1.4 Unique pain pathophysiology in older adults

The neurophysiological mechanism of pain in older adults has been shown to be substantially altered when compared to the pathways in younger adults. Neurochemical and electrophysiological aspects of nociceptive pain pathways change as a person ages [4]. There is a known age-related loss in several relevant neurotransmitters including serotonin, gamma-aminobutyric acid as well as in opioid receptors, and a decrease in the function of the descending inhibitory pain pathway. A slight increase in pain threshold, or a reduced sensitivity to mild pain, has been demonstrated in older adults, particularly to thermal stimuli [13].

From a treatment perspective, frail older adults typically have reduced capacities for drug absorption, distribution and metabolism, and a higher risk for drug toxicity [14]. There is also evidence to suggest that the physiological response to pain may be blunted in older adults with dementia [15].

Table 1.12-1 [16] summarizes the many physiological and pharmacokinetic changes that are common in older adults. These factors are the basis for the unique issues with pain assessment, management, and expected response to therapy in older adults [15].

1.5 Types of pain

While the specific nature and intensity of pain is subjective, clinically meaningful categories exist. Pain can be usefully characterized as acute or chronic, and further divided into different pathophysiological subtypes [17]:

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  Acute pain is characterized by an abrupt onset, linked to a specific insult and only lasts for a relatively short period of time.

  
  
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  Chronic pain persists for more than 3–6 months and is characterized by the ongoing pain in the absence of specifically identified stimuli. Lower socioeconomic status, inactivity, chronic illness, and lack of social support are some of the factors that have been associated with the development of chronic pain in older adults [17].

There are three different pathophysiological subtypes of pain: nociceptive, neuropathic and mixed [4]:

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  Nociceptive pain is due to the activation of sensory receptors by noxious stimuli, and can be further divided into either somatic or visceral pain. Somatic pain tends to originate in the skin, muscle or bone and is often easily localized. Pain related to an acute hip fracture is typically a nociceptive, somatic type of pain. Visceral pain is a referred pain originating from an internal organ such as the heart, lungs or gastrointestinal (GI) tract. Usually visceral pain is relatively difficult to localize and is described as aching, dull or vague.

  
  
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  Neuropathic pain is caused by irritation or inflammation of nerve fibers and/or neurons, and is usually described as burning, tingling or numbness. It is usually localized easily but may have a radiating component that follows the path of the nerve itself. This can also be seen in hip fracture patients postoperatively if nerve fibers were disturbed during the fracture or the procedure or by postoperative edema and inflammation. Neuropathic pain may have a variable or inadequate response to typical pain medications, including antiinflammatory analgesics or opioids. Nontraditional pain medications like anticonvulsants and antidepressants may be more effective for neuropathic pain.

  
  
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  The third subtype of pain is a mixed type with features of both nociceptive and neuropathic pain; this typically requires multiple different modalities to treat adequately. One example of this mixed type is a vertebral fracture with nerve impingement resulting in both somatic and neuropathic components [4, 16, 18].

2.1 Self-report

Self-report is the primary method in pain assessment for older adults. This should be attempted first; if the patient is unable to respond appropriately, then other clinical indicators of pain should be sought. Autonomic symptoms such as diaphoresis, hypertension and tachycardia can sometimes suggest a high likelihood of pain. The following scales are commonly used for pain assessment:

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  The numerical rating scale (NRS) is a verbally obtained numerical pain scale ranging from 0 to 10 (0 is considered no pain and 10 is considered the most severe pain imaginable); patients are asked to ascribe a number to their pain from this continuum. The NRS is the most common and most valid pain scale in older adults capable of self-report [19].

  
  
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  The Visual Analog Scale is a related tool that prompts a patient to indicate a pain rating on a printed line between two extremes of no pain (0) and excruciating pain (10). This has been shown to be less effective in older adults and has a higher error rate [20].

  
  
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  The Verbal Descriptor Scale (VDS) has also been validated in older adults and consists of verbal indicators (eg, mild, moderate, severe) to quantify the intensity of a patient′s pain. The VDS is preferred by older adults and has been demonstrated to be effective in moderate and severe dementia [19].

  
  
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  Other self-report options include the Faces Pain Scale, commonly used in children but has also been validated in older adults [21]. It requires the patient to identify the facial expression which best indicates the pain they are experiencing. This can be helpful in older adults who are nonverbal.

All of these tools have limitations including inability to describe pain location, problems with identifying dynamic pain with activity, and inaccuracies with monitoring the response to the treatment of chronic pain.

2.2 Cognitively impaired patients

The assessment of pain in a nonverbal or severely cognitively impaired patient can present a dilemma for clinicians and nurses. In order to obtain an accurate assessment, clinician and staff observation of nonverbal indicators is necessary. The American Geriatrics Society (AGS) recommends the evaluation of six behavioral domains including facial expressions, verbalizations/vocalizations, body movements, changes in interpersonal interactions, changes in activity patterns, and changes in mental status [16].

A number of behavioral pain assessment tools have been validated for use in older adults with severe cognitive impairment [20]. These include the Pain Assessment in Advanced Dementia scale [8], which consists of five items that aid in the interpretation of nonverbal pain as seen in Table 1.12-2 .

Other validated scales include the Abbey pain scale and the pain assessment checklist for seniors with limited ability to communicate [20, 21]. All of these can be used to assess and track acute pain as well as measure the effectiveness of the treatment.