Evaluation of Pain
Clinicians should evaluate the cause, severity, and nature of the pain and its effect on activities, mood, cognition, and sleep. Evaluation of the cause of acute pain (eg, back pain, chest pain—see elsewhere in The Manual) differs from that of chronic pain (see Chronic Pain).
The history should include the following information about the pain:
The patient’s level of function should be assessed, focusing on activities of daily living (eg, dressing, bathing), employment, avocations, and personal relationships (including sexual).
The patient's perception of pain can represent more than the disorder's intrinsic physiologic processes. What pain means to the patient should be determined, with emphasis on psychologic issues, depression, and anxiety. Reporting pain is more socially acceptable than reporting anxiety or depression, and appropriate therapy often depends on sorting out these divergent perceptions. Pain and suffering should also be distinguished, especially in cancer patients (see Management of Adverse Effects of Cancer Therapy : Pain); suffering may be due as much to loss of function and fear of impending death as to pain. Whether secondary gain (external, incidental benefits of a disorder—eg, time off, disability payments) contributes to pain or pain-related disability should be considered. The patient should be asked whether litigation is ongoing or financial compensation for injury will be sought. A personal or family history of chronic pain can often illuminate the current problem. Whether family members perpetuate chronic pain (eg, by constantly asking about the patient's health) should be considered.
Patients and sometimes family members and caregivers should be asked about the use, efficacy, and adverse effects of prescription and OTC drugs and other treatments and about alcohol and recreational or illicit drug use.
Pain severity should be assessed before and after potentially painful interventions. In verbal patients, self-report is the gold standard, and external signs of pain or distress (eg, crying, wincing, rocking) are secondary. For patients who have difficulty communicating and for young children, nonverbal indicators (behavioral and sometimes physiologic) may need to be the primary source of information.
Formal measures (see Figure: Some pain scales for quantifying pain as it is occurring.) include verbal category scales (eg, mild, moderate, severe), numeric scales, and the Visual Analog Scale (VAS). For the numeric scale, patients are asked to rate their pain from 0 to 10 (0 = no pain; 10 = “the worst pain ever”). For the VAS, patients make a hash mark representing their degree of pain on an unmarked 10-cm line with the left side labeled “no pain” and the right side labeled “unbearable pain.” The pain score is distance in mm from the left end of the line. Children and patients with limited literacy or known developmental problems may select from images of faces ranging from smiling to contorted with pain or from fruits of varying sizes to convey their perception of pain severity. When measuring pain, the examiner should specify a time period (eg, “on average during the past week”).
Some pain scales for quantifying pain as it is occurring.
Assessing pain in patients with disorders affecting cognition, speech, or language (eg, dementia, aphasia) can be difficult. Pain is suggested by facial grimacing, frowning, or repetitive eye blinking. Sometimes caregivers can describe behaviors that suggest pain (eg, sudden social withdrawal, irritability, grimacing). Pain should be considered in patients who have difficulty communicating and who inexplicably change their behavior. Many patients who have difficulty communicating can communicate meaningfully when an appropriate pain scale is used. For example, the Function Pain Scale has been validated and can be used in nursing home patients who have Mini-Mental State Examination scores of ≥ 17.
No validated instruments are available to assess pain when neuromuscular blockade is used to facilitate mechanical ventilation. If the patient is given a sedative, the dose can be adjusted until there is no evidence of consciousness. In such cases, specific analgesics are not needed. If, however, the patient is sedated but continues to have evidence of consciousness (eg, blinking, some eye movement response to command), pain treatment should be considered based on the degree of pain usually caused by the condition (eg, burns, trauma). If a potentially painful procedure (eg, turning a bedbound patient) is required, pretreatment with the selected analgesic or anesthetic should be given.