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Palliative Care Perspectives : Chapter 4: Pain Management : Classification of Pain

Acute Pain

We all have experienced acute pain. Bee stings, bumped knees, and bone fractures are simple examples. Most acute pain serves a clear purpose: some problem needs to be addressed. Acute pain is characterized by help-seeking behavior. In most cases people cry out and move about in a very obvious manner. Physiologic responses to acute pain include tachycardia, tachypnea, and sweating due to discharge in the sympathetic nervous system. It is easy to recognize and empathize with acute pain. It is practically automatic. We wince if we see severe, acute pain and respond with our own "sympathetic" discharge.

The treatment of acute pain can be difficult in that the intensity of pain may change dramatically over a short period of time. Physicians may have trouble adjusting pain medications rapidly enough to match the level of pain being experienced because pain intensity tends to escalate and decrease swiftly. Both under- and overtreatment can easily occur. Undertreatment risks excessive suffering. Overtreatment poses real medical risks. Thus, as acute pain changes rapidly, treatment of such pain requires frequent reassessment of the patient's status in order to avoid extremes of under- and overtreatment.

Chronic Pain

Chronic pain is very different from acute pain. It serves no biological purpose. While the suffering engendered may be as great as is that in acute pain, it is subjectively experienced and objectively displayed in a very different way. For reasons not well understood, chronic pain is characterized by physical and mental withdrawal. Vegetative signs very similar to those found in depression, such as anorexia, anhedonia, lethargy, and sleep disturbance are often present. Chronic pain frequently coexists with depression, making it difficult at times to distinguish between the two. Obvious displays of distress, as are found in acute pain, are usually absent. Chronic pain is very difficult to recognize. Even when recognized we tend not to experience the same intense, visceral empathy that arises so easily in the presence of acute pain. Lack of recognition of chronic pain and difficulty empathizing with it are major barriers to successful treatment.

It is difficult to judge by observation alone the degree of chronic pain suffered. Both family members and professional health care workers tend to miss the mark. Tragically, the correlation between a patient's and another's assessment of pain intensity is poorer at higher degrees of pain. In one study using visual analog scales (VAS) from 0 to 10 to measure pain intensity, correlation between the observers' estimated intensity score and that reported by the patient was worst at high levels of pain, scores of 7 to 10 (severe to unendurable).6 This stands in dramatic contrast to our experience with acute pain; the more severe the acute pain the easier it is for us to recognize. From this and other studies it has been concluded that for patients with chronic pain, we cannot simply "see" if a patient is in pain. We are, in effect, "color-blind" to chronic pain. We also cannot judge the degree of pain by measures such as noting how calm or disturbed a patient appears. In a manner of speaking we suffer a disability. As with any disability, we must try to find ways to compensate. In order to determine how much pain a patient is in, we have to ask. If possible, it is advisable to use a scale of pain intensity to communicate intensity of pain. Numeric scales from 0 to 5 or 0 to 10 or visual analogue scales, some with pictures reflecting varying degrees of distress, are commonly used. These allow a better assessment of pain intensity and a more accurate measure of changes with therapeutic intervention.

Is it reasonable or necessary to measure pain on a routine basis? I would argue that the evidence is overwhelming that people simply lack the proper receptors to detect chronic pain (much like we cannot see blood pressure). It would be wonderful if all clinicians routinely asked patients about their pain. However, the evidence is also strong that clinicians have resisted efforts to improve pain assessment less formally. However, is such measurement scientific?

Pain management would be infinitely easier if we had something like an O2 saturation meter to measure pain - something like the tricorder in Star Trek movies. Clinicians prefer hard data and become uncomfortable with subjective reports. In an absolute sense we cannot know if one patient's 7 to 10 pain is the same as that of another. However, studies have demonstrated that the individual patient is consistent in reporting pain scores. That is, intra-rater reliability has been validated.7 I think of pain scores as imperfect tools to compensate for our collective disability.

Even so, what if people lie? In hospice literature it has been said that pain is whatever the patient says it is. This seems a bit simplistic to me. While it is true that we are color-blind to chronic pain, it is also true that some patients may be less than honest about their pain. Patients may fabricate or exaggerate symptoms for psychological reasons or secondary gain. Patients with very real chronic pain may also learn to exaggerate their pain and become demanding, as they believe physicians will not otherwise take them seriously, a process called "pseudoaddiction."8 Paradoxically, this may arouse suspicion in the practitioner that the pain is not "real." There is no easy way to tell what is real. However, common sense and a trusting relationship between provider and patient go a long way. As a general rule, if the complaint of pain is plausible and if there are no very good reasons for doubting the patient, believe it. My philosophy is that ties go to the patient. Of two possible "sins" in pain management, the sin of ignoring real pain seems greater than does the sin of occasionally being fooled by a patient.

Palliative Care Note
When not sure whether the patient is telling the truth or not about pain, ties go to the patient.

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Keywords: Pain management
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Palliative Care Perspectives

James L. Hallenbeck, M.D.

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Copyright 2003 by Oxford University Press, Inc.

The online version of this book is used with permission of the publisher and author on web sites affiliated with the Inter-Institutional Collaborating Network on End-of-life Care (IICN), sponsored by Growth House, Inc.