Martha L. Twaddle MD
Kelly J. Cooke DO
Essentials of Diagnosis
The International Association for the Study of Pain (IASP) defines pain in terms of the stimulus and response: “Pain is an unpleasant sensory and emotional experience associated with actual and potential tissue damage, or described in terms of such damage.”
“Pain is whatever the experiencing person says it is existing whenever he says it does.” McCaffrey
Differences Between Acute & Chronic Pain
Pain is typically described as acute or chronic. Many specialists use the term “persistent” in place of chronic or combine the two. The designation between these types of pain has to do with the duration of the symptom as well as the physiologic response of the person (Table 2-1).
Typically, acute pain is associated with immediate tissue injury and is of limited duration. The pain initiates a warning response to the person to avoid further injury by activating the sympathetic nervous system. Thus, the patient would experience vasoconstriction, rapid pulse, and “fight or flight” physiology. In addition, the patient is often agitated and may groan and show signs of heightened awareness and activity.
In severe acute pain, such as labor or myocardial infarction, patients may be immobilized as well as demonstrate dissociation and decreased responsiveness to their environment. Acute pain usually responds to treatment. The ideal therapy is prompt and sufficient administration of analgesic medication along with reassurance and support.
Typically, chronic or persistent pain perpetuates long after the tissue injury has resolved or healed, so the reason for the pain is not obvious. In patients with chronic pain, physiologic adaptation to the persistent pain stimulus may be accompanied by the following signs and symptoms: depressive symptoms, withdrawal, anorexia, fatigue, hypersomnolence or insomnia, irritability or mood lability, lack of initiative and inactivity. These signs and symptoms may be subtle and require observation over time and input from family, friends, and caregivers about any behavioral changes.
Patients may not necessarily look like they are experiencing pain; their pulse and facial expressions would not reflect the stimulus of pain. Patients in persistent pain can interact and even laugh, but distraction cannot sustain a pain-free state.
Chronic or persistent pain tends to respond poorly to treatment because it is deeply embedded within the physiology and psychology of the patient. The ideal management requires a multidisciplinary, whole-person approach and long-term care.
Patients should be allowed to describe their pain in their own words. The clinician can then ask specific questions to elicit the adjectives that will help identify the cause, facilitate the diagnosis as well as determine possible approaches to alleviate the pain.
Table 2-1. Characteristics That Differentiate Acute from Chronic Pain.
The clinical terms that will help describe the quality and character of pain include acute or chronic; diffuse or localized; throbbing or achy; dull or cramping; burning, tingling, stabbing, or shooting; sharp or tender; constant or intermittent; and breakthrough or incident.
Describing the pain as acute or chronic establishes the timing and duration of the pain (see Table 2-1) and thus the mechanisms involved. The term “diffuse” suggests a central process or an inflammatory condition. Localized pain is associated with a discrete injury, a peripheral nerve lesion, or the immediate postoperative state.
Throbbing aching pain is suggestive of bone disease, such as bone metastases or muscle strain and soft tissue injury. The terms “dull” and “cramping” are often associated with visceral pain states, such as irritation or inflammation of the viscera (as in organs) or functional pain syndromes involving the intestines.
The descriptors burning and tingling or stabbing and shooting are often associated with nerve injury or pathologic changes involving nerves and the transmission of the pain stimulus.
When the terms “sharp” or “tender” are used, clarification is necessary. Sharp can indicate sudden and acute or may be used as part of the description for nerve-related pain. Tender may reflect a lower level of pain or be used to describe aching, dull pain.
Constant or intermittent refers to the timing of the pain. Constant pain means that it is always present. This type of pain is best treated with scheduled medication around the clock. Intermittent pain, however, is unpredictable. Therefore, it is best treated with medication as needed.
The terms “breakthrough” or “incident” pain are not synonymous. Breakthrough pain describes an unexpected pain exacerbation that suddenly surpasses the analgesia provided by a previously effective therapy or scheduled medication. It requires prompt response to rescue the patient from pain. Incident pain occurs with a specific activity, such as coughing, lifting, or walking; it is therefore predictable and often reproducible. In order to prevent the pain from occurring, it is best treated with therapies or medication before the specific activity.
By convention, pain is typically classified in terms of pathophysiology and is referred to as nociceptive, inflammatory, or neuropathic pain syndromes (Table 2-2). Additional pain syndromes usually involve combinations of these classifications or are described in terms of pain due to an overarching diagnosis, such as cancer pain (see Pain Syndromes section).
This type of pain involves stimuli ascending via normal nerves traveling along sensory neurons and ascending via the spinothalamic pathways of the spinal cord. It includes both somatic and visceral pain.
Somatic pain is typically well localized in the superficial cutaneous or deeper musculoskeletal structures (eg, immediate postoperative wounds, bone metastases, muscle sprain). Visceral pain is usually poorly localized and often referred from deeper structures, such as the intestines (eg, constipation, early appendicitis).
Inflammatory pain is transmitted via normal nerves and pathways such as in nociceptive pain. However, the degree of tissue damage leads to the activation of acute and chronic inflammatory mediators that potentiate pain, lower thresholds for conduction, and sensitize the central nervous system to the incoming stimulus.
Table 2-2. Pathophysiologic Classifications of Pain.
Examples include chronic inflammatory conditions, such as arthropathies and arthritis, ischemic vasculopathies, later postoperative wounds, and burns.
This type of pain arises in an area that is neurologically abnormal and is caused by a lesion of the peripheral or central nervous system. Most mechanisms of injury are poorly understood but may include incisional or crush damage of nerve tissue and nutritional, chemical, is-chemic, metabolic, neoplastic or paraneoplastic insults to the peripheral or central nervous system.
Pain is typically perceived or described as being electrical in quality (ie, burning, shooting, stabbing, buzzing, tingling) or associated with numbness or abnormal temperatures. The sensation in the area affected and involved in the pain is usually abnormal. For example, non-noxious stimuli (such as touch, light pressure, or temperature) are often either amplified hyperalgesic or numbed. The sensation created by the stimuli may be unassociated with the stimulus itself (ie, light feather touch can hurt, cold may feel hot, sharp prick stimuli may be numbed). Examples of neuropathic pain include postherpetic neuralgia, phantom limb pain, postthoracotomy chest pain, and diabetic neuropathy.
Carr D, Novak G, Rathmell JP, et al. The Spectrum of Pain: Case-Based Medicine Teaching Series. New York, McMahon Publishing Group, 2005. McCaffery M. The patient's report of pain. Am J Nurs. 2001;101:73.
Woolf CJ. Pain: Moving from symptom control toward mechanism-specific pharmacologic management.Ann Intern Med. 2004;140:441.
Assessment of Pain
The history taking uses questions that are open-ended and directed toward understanding the pain syndrome and ideally finding a reversible cause to the pain (Table 2-3). Important information to gather includes the following: onset and duration, location, severity or intensity rated using a measurement tool, quality or character, aggravating factors, alleviating factors, and any previous treatments and their effect.
Additional questions should address how the pain impacts the patient's functional status, specifically activities of daily living (ADLs), instrumental activities of daily living (IADLs), and advanced activities of daily living (AADLs) (Tables 2-4, 2-5 and 2-6). This functional assessment and documentation is particularly important in
follow-up since the restoration of function can attest to the impact of pain relief therapies.
Table 2-3. Suggested Open-Ended Questions to Ask during the Patient Interview.
The use of an anatomic figure to indicate areas of pain can aid in history taking. Having the patient label areas of pain on a drawing can be compared with a similar schematic generated during the physical examination. This may present a visual of pain that gives insight into cause.
The physical examination includes assessment of the presence of signs and symptoms that might reflect the pathophysiology of the underlying pain. The vital signs may be elevated in patients with acute pain or normal in patients with persistent pain. The appearance of the patient may reflect discomfort or may reveal a flattened affect. Patients often put forth great effort to obscure the level of their distress. Examining the pain area should include looking for distortions in anatomy, changes in color or consistency of the skin, and spasms or fasciculation of the underlying muscle. Palpation should be gentle initially, building gradually to assess for deeper pathology.
Table 2-4. Additional Questions to Assess How Pain Impacts Functional Status.
Table 2-5. Numeric Scale to Describe Pain and Affect on ADLs.
Palpating the same area with different approaches gives insight into the reproducibility of the pain. Distracting the patient during palpation can sometimes quiet anticipatory pain and guarding.
The physical examination can reflect the pathophysiology causing pain. For example, nociceptive somatic pain typically intensifies with palpation of a specific area (ie, pressure on a rib eliciting focal pain might reflect fracture or metastatic disease). Pain that intensifies with activity may reflect bone or muscle abnormalities or injuries. An example of nociceptive visceral pain includes sudden onset of retrosternal chest pain radiating to the jaw caused by myocardial ischemia. Physical palpation does not exacerbate or increase the pain. Another example of nociceptive visceral pain is generalized discomfort of the abdomen, many times associated with nausea. Palpation only worsens pain once inflammation has begun.
Rapid distention of the renal collecting system associated with blockage causes severe pain. The distention of the kidney can cascade into splinting and spasm of the lateral abdominal muscles. Depending on where in the renal pelvis and ureter the obstruction exists, the pain will be referred to varying locations:
Table 2-6. Assessing Functional Status by Evaluating Activities of Daily Living.
Palpation of the site of pain will not increase the pain complaint.
Inflammatory pain is aggravated by deep breathing; rebound of the abdomen would likely reflect inflammatory pain. Pain that is intensified with a full inspiration and associated with abnormal lung sounds or rubs indicates pleuritic inflammation. Pain associated with reddened, swollen joints suggests inflammatory arthropathies.
Neuropathic pain is characterized by the following: allodynia, a condition in which ordinarily nonpainful stimuli evoke pain; hyperalgesia, an exaggerated response to nonpainful or mildly painful stimulus; causalgia, abnormalities of skin temperature and color compared with surrounding areas; atrophy and loss of hair in affected area; weakness of a muscle group associated with pain; and numbness to stimuli in the painful area.
The expansion of the history and physical to include the input of a multidisciplinary or interdisciplinary team is the ideal approach in the assessment and management of pain. This approach incorporates not only the physical aspects of pain but also explores and documents the psychological/psychiatric, social, spiritual/religious, and cultural aspects of pain that would augment and complicate the patient's suffering.
Questions are directed toward manifestations of stress, mechanisms of coping, signs and symptoms of depression and anxiety, and behavior patterns that may help or hinder rehabilitation.
Examples of behaviors that may reflect pain include changes in appetite, such as anorexia; sleep disturbances, such as restlessness and frequent awakenings; agitation or aggressiveness; the above prompted by physical touch or changes in position; and decreased socialization and withdrawal.
When using behavioral cues for assessment, a patient's behavior will need to be reassessed after treatment with analgesic drugs. There may not be a clearcut response. Thus, a defined trial of a medication with ongoing observation will be necessary.
Remember, if pain has been uncontrolled for a period of time and thus associated with sleep disturbances and sleep deprivation, relief of pain may initially be associated with somnolence. Thus, it is critically important to allow several days (more than 72 hours) or more of the medication trial to truly assess its impact on behavior and function.
The impact of pain may have significant financial and social repercussions. These can magnify the experience of pain and aggravate feelings of helplessness, hopelessness, and despair. The social assessment could also involve how a family system is affected by the patient's pain and an assessment of possible equipment or home environment needs.
These assessments include elucidation of faith traditions, rituals, or lack thereof. For some, the exploration of this dimension of self serves as a keyhole into unspoken hopes and fears.
Patients may articulate how faith or religious rituals help them cope with the impact of pain or how they perceive their pain is a form of punishment for prior deeds.
A cultural assessment represents more than documentation of heritage; it includes ethnicity, language, family/community hierarchy and rituals as well as dietary practices. This facet of whole-person care may give insight into cultural preferences regarding disclosure of medical information and decision making. It is key to remember that spiritual/religious and cultural aspects of a patient often impact his or her choice of descriptors, tolerance of pain, or acceptance of medications or other treatment modalities.
Though there is no single test or series of tests that can definitely demonstrate the nature of the pain complaint, diagnostic testing can give insight into possible causes.
Plain films can help elucidate structural changes in bone or soft tissue that correlate with the area involved in pain. These films may show bone damage from fractures or neoplastic disease, or the loss of bone integrity impinging on neighboring nerve or soft tissue. In the case of spinal films, abnormal findings can exist in people who have no sensation of pain, and relatively normal-appearing tissue or bone can be the source of significant pain stimuli since inflammation is not evident on radiographic films.
Electromyography and electroneuromyography may give evidence of nerve and muscle injury. However, these studies are highly individualized and the electrodiagnostician must thoughtfully plan the approach and scope of testing to narrow or clarify the possible areas of injury and associated pathology.
Pain Rating Scales
The severity or intensity of pain can be assessed using pain scales. It is important to choose a developmentally appropriate scale based on the age and cognitive status of the patient. The most extensively tested multidimensional scale for assessment is the McGill Pain Questionnaire. It takes 5 to 15 minutes to complete and is more thorough than other scales. The most commonly used scale is the Numeric Pain Intensity Scale (0 to 10). With this scale, 0 corresponds to no pain and 10 the worst imaginable pain.
For patients who have difficulty choosing a number between 0 and 10, using a schematic similar to a ruler might be easier because the patient can point to a number along a continuum (Figure 2-1). Alternatively, some patients find it is easier to rate their pain by merely using the words mild, moderate, or severe. For others, the Visual Analogue Scale (VAS) is beneficial. Here the patient has the opportunity to shade in the amount of pain that exists along a continuum from no pain to worst possible pain (Figure 2-2). A final common pain scale is the Wong Baker FACES Scale (Figure 2-3). This scale shows six faces that depict a range of anguish secondary to pain. Figure 2-4 shows a comprehensive pain assessment tool. Pain distress can be tied to functional status. Asking how pain affects activity or rating pain along with its functional impact allows a means to track improvement in a multidimensional outcome (see Table 2-6).
Figure 2-1. The Numeric Pain Intensity scale.
Figure 2-2. Visual Analogue Scale.
Moskowitz E, McCann CB. (1957). Functional disability and handicap. J Clin Oncol. 1995;9:2149-2151.
Memorial Sloan-Kettering Pain Assessment Card. http://www.mskcc.org/mskcc/html/5855.cfm; April 8, 2005.
Pain Assessment in the Cognitively Impaired
In several studies, particularly targeting nursing home patients, the results demonstrate that there is no evidence of the masking of pain complaints by cognitive impairment. Although many older patients and cognitively impaired patients may underreport their experience of pain, their self-reports are found to be no less valid than other individuals who are cognitively intact. The challenge of assessing pain in the cognitively impaired has to do with the tools that are used to glean the results.
Assessing pain, however, in elderly patients who cannot respond verbally will negate the value of using any type of verbal descriptive tools, such as the Numeric Pain Scale described earlier. Functional status tools may be influenced by cognitive decline or morbidities such as hemiplegia, which may not necessarily involve pain.
In assessing the severely cognitively impaired patient, referring to the tools used by pediatricians may be helpful. For example, the Wong Baker FACES Scale was developed for children and could be helpful in assessing pain in the cognitively impaired patient (Table 2-7).
Figure 2-3. Wong Baker FACES Scale. (Wong DL, Hockenberry-Eaton M, Wilson D, Winkelstein ML, Ahmann E, DeVito-Thomas PA. Whaley and Wong's Nursing Care of Infants and Children, ed. 6. St. Louis, 1999, Mosby, p 1153. Copyrighted by Mosby-Year Book, Inc. Reprinted by permission.)
Pain & Delirium in the Cognitively Impaired Patients
There is frequently an expressed concern that the use of analgesics can contribute to delirium in older patients. Studies of patients who have had hip fractures demonstrated that it is the undertreatment of pain that is a significant contributing factor to delirium. In fact, insufficient doses of opioids after the fracture or its repair are associated with an increased risk of delirium in both cognitively intact and cognitively impaired patients.
In hospital, it is common to write a prescription for pain medications to be given on an as-needed basis. However, the cognitively impaired patient may not be capable of interpreting their discomfort and translating this into a request for analgesics.
Closs SJ et al. A comparison of five pain assessment scales for nursing home residents with varying degrees of cognitive impairment. J Pain Symptom Manage.2004;27:196.
KovachCR et al. The assessment of discomfort in dementia protocol. Pain Manag Nurs. 2002;3:16.
Krulewitch H et al. Assessment of pain in cognitively impaired older adults: a comparison of pain assessment tools and their use by non-professional caregivers. J Am Geriatr Soc. 2000;48:1607.
Litaker D et al. Preoperative risk factors for postoperative delirium. Gen Hosp Psychiatry. 2001;23:84.
Manz BD et al. Pain assessment in the cognitively impaired and unimpaired elderly. Pain Manag Nurs. 20001:106.
Morrison RS et al. A comparison of pain and its treatment in advanced dementia and cognitively intact patients with hip fracture. J Pain Symptom Manage.2000;19:240.
Morrison RS et al. Relationship between pain and opioid analgesics on the development of delirium following hip fracture. J Gerontol A Biol Sci Med Sci.2003;58:76.
Proctor WR et al. Pain and cognitive status among nursing home residents in Canada. Pain Res Manag. 2001;6:119.
Taylor LJ et al. Pain intensity assessment: a comparison of selected pain intensity scales for use in cognitively intact and cognitively impaired African American older adults. Pain Manag Nurs. 2003;4:87.
Figure 2-4. Comprehensive pain assessment tool.
Table 2-7. Comparison of Pain Scales.
Grouping pain complaints based on physical findings or underlying diagnoses gives rise to many types of pain syndromes. As the understanding of pain pathophysiology expands, syndromes are better understood in terms of their defined pathology and mechanisms of pain transmission.
The pain associated with cancer may be caused by the disease or may result from some of the therapies used in treating the disease. The pain may also result from a co-morbidity that is activated or aggravated in the diagnosis or treatment of the primary neoplastic process, such as arthritis or migraine.
Cancer pain is not unique in its pathophysiology; it is both acute and chronic and nociceptive, inflammatory, and neuropathic in its physiology.
Unremitted cancer pain may have significant impact on the patient's well-being and ability to undergo and tolerate treatments such as chemotherapy and radiation. Unrelieved cancer pain may have such a negative impact on the functional status of the patient that it can influence the actual prognosis in the course of disease.
Functional pain lacks a recognizable cause; it has no clear peripheral or central pathophysiology, and yet is associated with persistent pain. The mechanisms are not yet well-defined and remain an area of active research.
Complaints of functional pain include irritable bowel syndrome, tension and migraine headache, as well as myofascial pain syndromes.
Complex Regional Pain Syndrome
The pathophysiology of this syndrome is complex and poorly understood. Complex regional pain syndrome (CRPS) is difficult to treat. It is believed to beneuropathic with dysautonomic signs. CRPS typically involves a constant burning sensation with intermittent paroxysms and includes two subtypes.
CRPS type I (previously known as reflex sympathetic dystrophy) is defined as continuing pain, allodynia, or hyperalgesia in which the pain is disproportionate to the inciting event and shows evidence of edema, changes in blood flow, and or abnormal motor function in the area of pain.
CRPS type II (previously known as causalgia) is similar to type I, but the presence of pain, allodynia, or
hyperalgesia is not necessarily limited to the distribution of the injured nerve.
Phantom limb sensations are common after the loss of a limb but not always associated with pain. Phantom limb pain is a chronic pain condition associated with perceived pain in the absent limb. Phantom limb pain can be severe and debilitating, usually involving neuropathic pain and central sensitization from peripheral nerve damage.
Bone pain is typically described as dull, aching, and constant; it is generally localized to the area of pathology with limited radiation. The pain can be aggravated by movement such as flexion or extension and sometimes by percussion.
Metastatic disease involving the long bones can be referred to the knee from lesions in the hip. Any patient with a malignancy who complains of dull, achy back pain should be assessed for an impending cord compression.
Typically, pleural pain is localized to the involved area; however, given the distribution of the pleura, it may involve the entire chest. The pain is described as sharp and shooting and is reproducible with a deep inhalation or cough. Pleural pain usually involves inflammation and nociceptive pathways. It may be associated with distinct physical findings such as a pleural rub with inhalation.
The term “plexopathies” refers to pain syndromes associated with an anatomically described peripheral nerve plexus. The neurologic abnormalities involve several nerves in the plexus. In the case of a brachial plexopathy, pain is aggravated by a deep breath or movement of the neck and shoulder. Deep palpation of the shoulder may reproduce pain or suggest fullness. The pain in brachial plexopathy may be related to neoplastic encroachment into the nerves, adhesions and impingement after infection, surgery, or radiation treatment.
Bladder pain is most commonly associated with inflammation and manifests with urgency, frequency, and loss of control. It is associated with painful spasms of the bladder itself, especially as it distends with urine.
Abnormalities of the rectum can often be painless until inflammatory changes occur or obstruction results. Complaints are usually associated with burning, bloody or mucoid discharge, and rectal urgency. Tenesmus is the sensation of incomplete emptying of the rectum and is usually associated with inflammation.
Galer BS et al. IASP diagnostic criteria for complex regional pain syndrome: a preliminary empirical validation study. International Association for the Study of Pain. Clin J Pain. 1998;14:48.
Assessment & Reassessment
The frequency of formal reassessment and redocumentation of pain depends on pain severity and the intensity of treatment. In severe pain states, when the titration of therapies is occurring frequently, pain levels should be reassessed and documented every 30 to 60 minutes using an effective tool. If pain is less intense and is perhaps being addressed with an oral pharmacologic regimen, reassessment and documentation of pain should initially be done in correlation with the half-life or pharmacodynamics of the medication being prescribed. For example, with a long-acting opioid with an 8-hour half-life, pain might be reassessed every 6 to 8 hours and dosing adjustments made every 24 hours. In a more stable pain state, reassessment and reaffirmation of pain management is individualized to the patients. Some patients need monthly follow-ups and reassessments, others can go quarterly or biannually with stability in their pain management approach.