4
Pain Management
Always the same. Now a spark of hope flashes up, then a sea of despair rages, and always pain; always pain, and always the same.
Leo Tolstoy, The Death of Ivan llyich
Pain is the most common presenting complaint to physicians in North America, and I suspect this is true in other regions of the world.1 It has been estimated that 85% to 95% of pain syndromes, including severe forms, such as cancer-related pain, can be adequately palliated using relatively simple techniques.2 However, pain is often undertreated. In one study of cancer patients at a famous cancer center, as many as 50% of cancer patients suffered unrelieved pain.3 Such undertreatment of pain is not isolated to cancer. The SUPPORT study demonstrated that 50% of the 9105 patients studied were estimated by surviving relatives as having moderate or severe pain 50% of the time or more in the last three days of life.4 A study of the treatment of nonmalignant pain in 49,971 nursing home patients found that 25% of patients with daily pain received no analgesics whatsoever. Advanced age (>85), male sex, cognitive impairment, and being a member of a racial minority were statistically significant risk factors for receiving no analgesics.5 A more recent study examined pain management in 8094 nursing home patients with cancer using the Medicare dataset.6 This was a follow-up study to determine if pain management had improved since a similar study in 1998 in which 29.4% of patients had daily pain. More than a quarter of these had no analgesics prescribed. The follow-up study demonstrated that pain was still undertreated in this population: 28.3% of patients had daily pain, of whom more than 17% received no analgesics, including 11.7% with daily severe pain. Patients over 85 and those with cognitive impairment were more likely to be undertreated. As I wrote in an associated editorial, clearly, we still have a long way to go.7
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. Transculturally, acute pain is characterized by help-seeking behavior. People cry out and move about in a very obvious manner. Physiologic responses to acute pain include tachycardia, tachypnea, and sweating due to sympathetic nervous system discharge. 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 radically 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 obvious biological purpose. While the suffering engendered may be as great as is that in acute pain, it is subjectively experienced and objectively displayed very differently. Chronic pain is characterized by physical and mental withdrawal. Vegetative signs 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.
What explains these differences between acute and chronic pain presentations? I suspect evolution played a role. The terms acute and chronic pain are rather misnomers, implying that the only differences between the two relate to acuity of onset and temporal duration. It is more complicated than that. Consider headaches. Most headaches come on acutely and do not last terribly long. And yet people tend not to writhe and call out. Rather, they withdraw in a manner typical of chronic pain. So, what is up? Some pains move people and other social animals to seek help from others, reflecting what we have come to call “acute pain.” However, other pains, which tend to be deeper in the body, reflect injuries less amenable to assistance from others. Perhaps better in such situations to hole up and hide in hopes of recovery. We call these “chronic pains.” One can imagine a survival advantage to both strategies. I suspect this also explains the different responses of people to the pain of others. We are hard-wired to respond to acute pain behaviors. Regrettably, we lack receptors to appreciate chronic pain in the same way.
It is difficult to judge by observation alone the degree of chronic pain suffered. 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).8 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 how calm or disturbed a patient appears. In a manner of speaking, we suffer a disability. As with any disability, we must find ways to compensate. In order to determine how much pain a patient is in, we need to ask.
The pain score so commonly used today is a proxy for our inability to see chronic pain.
Numeric scales from 0 to 10 or visual analog scales, some with pictures reflecting varying degrees of distress, are commonly used. These may allow a better assessment of pain intensity and a more accurate measure of change with therapeutic intervention, although some caution is urged in interpreting patients’ responses. Clinicians have been taught that reported pain scores are a measure of the amount of pain being experienced at a particular moment in time, and that certainly can be the case. As a general rule, scores of 0 to 4 reflect mild, 5 to 7 moderate, and 8 to 10 severe pain. Over time patients and families have been acculturated to communicating about their pain using these scores. However, people do not experience pain in terms of numbers. Nor is pain as simple as a here-and-now blip of physical severity. Physiologic pain signals are interpreted as to their meaning and projected from the past into the future to determine possible trends. Is the pain getting better or worse? What does it mean?
I recall being at the dentist once, having a cavity filled. The dentist asked me to raise my finger if I felt excess discomfort. I began experiencing some pain. To distract myself I imagined asking myself what my pain score was. A 2 or 3, I thought. I could put up with it. Besides, it was only going to last a few minutes more. The pain didn’t represent anything terrible—once I got my cavity filled, I’d be in better shape. So, my finger stayed down. But what if I thought that pain was going to continue indefinitely or worsen? No, that was not OK. My finger would go up in a flash. Maybe my score was closer to an 8 . . . The idea of that pain going on and getting worse would have been too much to bear.
As this simple example demonstrates, I believe most people coopt pain scores to communicate the severity of their distress and the urgency of response desired from other people. Hospital inpatients learn over time that if they report a pain score of 0 to 3 to the nurse, the response and sometimes even the medication they receive from the nurse is very different from the response to a reported score of 8. Thus, reported pain scores are quite different from physiologic measurements such as oxygen saturation percentages. Reported scores are fundamentally a relational form of communication, as will be discussed more in Chapter 8, Communication. That is, something is being asked of the other—to take an action (or not)—and the message communicates the urgency of any such action.9
In an absolute sense we cannot know if one patient’s 7 to 10 pain is the same as that of another or if both people are trying to communicate the same amount of distress. However, studies have demonstrated that individual patients are generally consistent in their reporting of pain scores. That is, intra-rater reliability has been validated.10 I recall one patient with advanced cancer who lived on a very narrow range of pain scores.
“How is your pain today?” I asked.
“Hmm, about a 1.3,” he replied.
“Is that OK for you?”
“Yes,” he said.
“What level would be too much—where you needed some additional help?”
“About a 2.4.”
This patient lived on a scale from 0 to 3. Conversely, I have had other patients whose scores on their best days are a 7 or 8 and say that their pain management is adequate. They live at the other end of the scale.
Palliative Care Note
After asking about patients’ pain scores, ask if their pain relief is adequate or not. Try to figure out what their internal ranges are.
An awkward question: What if people lie? 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, secondary gain, or because of addiction. 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, something called “pseudo-addiction.”11 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.
While we can never know if one person’s 8/10 pain is the same as another’s, and people may be less than truthful in reporting their experience, the relational aspect of the communication is usually honest in what is being asked of us. If, for example, a person suffering substance abuse tells us that on a scale of 0 to 10 his or her pain is a “15,” this is mathematically impossible. And yet it is truthful in communicating the urgency of response desired.
Types of Pain
Nociceptive (Tissue) Pain
Nociceptive pain results from tissue damage. Intact neurons dutifully report damage, and pain is experienced. Nociceptive pain can be subdivided into somatic and visceral (gut) pain. Nociceptive pain can be experienced as sharp, dull, or aching. There may be radiation of the pain, especially visceral pain, but it will not be in a direct nerve distribution. For example, gallbladder pain can radiate to the scapula. Nociceptive pain is generally responsive to nonsteroidal anti-inflammatory drugs (NSAIDs) and opioids. Conditions associated with inflammation, bone pain, and joint disease are particularly responsive to NSAIDs.
Neuropathic (Nerve) Pain
Neuropathic pain may occur when there is either damage to or dysfunction of nerves in the peripheral or central nervous system. Faulty signals are sent to the brain and experienced as pain. Neuropathic pain can be either peripheral (outside the central nervous system) or central in origin. Examples of neuropathic pain include diabetic neuropathy, trigeminal neuralgia, postherpetic zoster neuralgia (peripheral pains), and the thalamic pain syndrome (a central pain). Neuropathic pain frequently coexists with nociceptive pain. Examples include trauma that damages tissue and nerves, burns (that burn skin as well as nerve endings), and external nerve compression. An example of the latter is when tumor bone infiltration in the spine compresses nerve roots.
Neuropathic pain is often described as having a burning or electrical quality. It may feel like a shock or lightning bolt. Sometimes stimuli that usually do not cause pain, such as light touch, may elicit a paroxysm of pain, called allodynia. A light stroke of the cheek that results in the sudden pain of trigeminal neuralgia is an example of this type of pain. Sometimes patients do not describe the sensation as being “painful” but rather as feeling unpleasantly strange or tingly, like an arm feels when it wakes up from “going to sleep.” This is called a dysesthesia. Diabetic neuropathy commonly results in this type of sensation.
Neuropathic pain in the peripheral nervous system frequently follows a nerve distribution. This distribution may replicate a particular nerve, as in sciatic pain or trigeminal neuralgia, or may represent the distribution of terminal nerve endings, as in the stocking-and-glove distribution of peripheral neuropathies.
Neuropathic pain is relatively resistant to NSAIDs and opioids, although they may be helpful in certain cases. The other major classes of medications useful for neuropathic pain, tricyclic antidepressants, anticonvulsants, and sodium channel blockers, will be discussed later.
Evaluation of Pain
As discussed earlier, pain is a complex and personal experience. It is affected by physiological, psychological, and spiritual factors. The evaluation of pain must consider these factors and their interactions that result in the experience of pain. A useful mnemonic in evaluating pain(s) is the acronym: NOPQRST.12
What makes the pain better or worse? Do certain activities or body positions alleviate or worsen the pain? How have previously tried medications affected the pain (partial relief, no relief, etc.)? This may provide an important clue as to the type of pain being experienced, if in doubt. While the focus of this text is on pharmacologic therapy, it is important to point out that nonpharmacologic interventions can have a significant (positive or negative) effect on pain.
Suffering: What impact is the pain having on the patient? The impact may be an internal experience, such as depression or a thought of suicide, or may directly affect the patient’s functioning. Sleep disturbances, difficulty walking, inability to work, and impairment of the activities of daily living may all reflect the pain experience. As obvious as this may seem, I am struck by how often we forget to ask how pain (or other symptoms) affect a person’s life. Perhaps it is because we assume that pain is simply awful—what more do we need to know? However, hearing how a person is suffering with pain (both the nitty-gritty [“I can’t work”] and the deep issues [“I wonder why God did this to me?”]) helps us understand and empathize with what the patient is going through. Personally, I have trouble relating to a number, but if a patient can begin talking to me about how life has changed for them, then I feel I can gain a small glimpse into their experience.
Pain Management Strategy
Having assessed the patient’s pain, a strategy for management should be developed. The discussion that follows emphasizes opioids because these are so commonly used in palliative care. However, this is not to suggest that opioids are more or less appropriate in any individual case. Sound clinical judgment must be used in selecting specific agents.
What Nonpharmacologic Approaches to Pain Should Be Adopted?
Although the emphasis here is on the pharmacology of pain management, the clinician should also consider other interventions in developing a strategy. How does the patient’s psychological state affect his or her pain? Is the patient depressed, anxious, or confused? How does the patient relate to his or her pain? Some patients want all pain to be abolished. Others may even want some pain to remain. (As one cancer patient put it, “If I didn’t feel some pain, how would I know what that cancer is doing in there?”) Some may see the pain as something to be conquered. Some may see it as something to be accepted. A thorough discussion of the psychological and spiritual aspects of pain is beyond the scope of this text. Often, assistance from others—psychologists, psychiatrists, social workers, and chaplains—will be necessary if proper care is to be delivered.
A variety of medical interventions other than medications may also be extremely useful. Radiation therapy and chemotherapy may help alleviate pain in patients with certain cancers. Nerve blocks, trigger-point injections, and (rarely) surgical approaches may also be useful. Physical therapy, occupational therapy, and massage therapy may help in certain cases. Experts in these areas should be consulted, as needed.
Principles in Choosing Medications
3. Think about who will be administering the medicine. A medication that requires injection might be very appropriate in a hospital or nursing home setting but difficult to administer at home. Competent patients administering their own medications may be better able to manage short-acting pain medications on an as-needed basis. In contrast, a demented patient with pain cared for in a nursing home or at home by family will probably receive inadequate analgesia when treated every 4 hours as needed, as family and staff may not assess pain regularly (especially at night) and the patient may be unable to advocate for him- or herself. Long-acting preparations of both NSAIDs and opioids may be more appropriate in such situations.
5. Identify the patient’s pain pattern and perform pattern matching with your therapy.
Pattern Matching
Management of pain is optimized when therapy overlaps the patient’s pattern of pain. This maximizes analgesia while minimizing side effects. In using opioids for therapy when pain increases, so should the drug dose. Similarly, when pain lessens, the drug dose should be decreased. Pain itself can counteract certain opioid side effects. In particular, sedation and respiratory depression are significantly blocked by pain.13 Thus, the goal in using opioids is to have pain signals and opioid signals neutralize each other.
Acute pain, with a pattern of rapid escalation and de-escalation, requires a short-acting agent and careful titration if pain is to be adequately managed and side effects avoided (Fig. 4.1).
Chronic pain typically has both a background “noise” of pain with intermittent spikes of incident, or breakthrough, pain. The general strategy for such pain is to use a long-acting agent to manage the background basal pain and a short-acting agent as needed for breakthrough pain (Fig. 4.2).
While these are common patterns, the patient’s individual pain pattern should be considered. For example, a patient may complain of pain only at night. This pattern should generate a “differential diagnosis” that may lead to important changes in therapy. This pattern may reflect pain worsened by lying down. Perhaps the patient is unable to get needed pain medications at night, as he or she is dependent on others, family, or nursing staff who may be less responsive during this time. Maybe he or she is no longer distracted, as in the daytime, which increases awareness of pain. Each of these underlying causes would require a different approach.
Let us review the classes of common analgesics before getting into a more in depth discussion of routes of therapy and dosing strategies for opioids (Fig. 4.3).
Figure 4.1. Acute pain-pattern matching. Analgesia is maximized and side effects are minimized when the rise and fall of the blood level of an analgesic closely overlaps the temporal pattern of a patient’s pain.
Figure 4.2. Chronic pain pattern. Generally, a long-acting medication for the baseline pain that is always present and a short-acting medication that rapidly peaks in tandem with an acute pain spike are needed.
Figure 4.3. Pain exacerbation at night. What is the “differential diagnosis” for this kind of pain?
Classes of Analgesics
Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)
NSAIDs are a mainstay in the management of mild to moderate nociceptive pain. As mentioned above, they are particularly useful in inflammatory states and in pain involving the musculoskeletal system.14
Palliative Care Note
For pain with a strong inflammatory component, if prescribing a medication, the onus is on you to justify why you would NOT use an anti-inflammatory agent, such as an NSAID or a steroid.
It is beyond the scope of this book to discuss the large number of NSAIDs available today. Rather, some guidelines for choosing and using them are offered.
3. For some patients NSAIDs may be as effective as or more effective than opioids in relieving pain. In such cases it may be a mistake to withhold this class of medication for fear of some of these side effects. Rather, additional steps may be necessary to minimize the risk. Proton pump inhibitors (PPIs) may significantly decrease the risk of gastric and duodenal bleeding.15 Identification and eradication of H. pylori infection may lessen the risk of bleeding with NSAIDs in those infected for both duodenal and gastric ulcers.15 When there is concern over renal function, careful monitoring of blood chemistries may allow early detection of adverse effects. If deterioration in renal function is detected, discontinuation of the NSAID usually results in a gradual return to baseline function. Use of COX-2 inhibitors (see below) may also help minimize risk.
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