Persistent pain

Jerome J. Epplin, Masaya Higuchi, Nisha Gajendra and Soumya Nadella

Prevalence and impact

Although pain is a ubiquitous experience, it remains a very complex and poorly understood phenomenon. The perception of pain is altered by many circumstances, such as the patient’s prior experience with pain, cultural background, emotional status, possibility of secondary gain, and personality. Pain may be acute, usually precipitated by an acute illness or injury. This type of pain is often associated with autonomic responses such as tachycardia, elevated blood pressure, or diaphoresis. The management of such pain is often straightforward and usually the pain is alleviated once the precipitating factor is treated.

However, especially among the elderly, pain is often ongoing without a single incident that causes the pain. Previously this was referred to as chronic pain. However, because the term chronic is frequently associated with a negative connotation the preferred term to describe such pain is persistent pain. Contrary to common misconceptions, persistent pain has a distinct pathologic basis, causing changes in the nervous system that often worsen over time.¹

Persistent pain is commonly encountered in a geriatric practice. It is estimated that 25% to 50% of the elderly may have persistent pain.² Sixty-five percent of nursing home residents report having inadequately treated pain.¹ However, a recent study³ looked at the long-term persistence of musculoskeletal pain in community-dwelling older adults. Over a 6-year period, approximately 20% of the study participants had no musculoskeletal pain, one third had persistent pain, one third had intermittent pain, and one sixth had pain in each of the 6 years. However, half of those with pain during one of the years had no pain during any of the other 5 years. This could imply that pain, while common, may be a more dynamic symptom than previously thought.

Persistent pain has a significant negative impact on patients’ lives (Box 27-1). Sleep disturbances, feelings of loneliness, depression, and social isolation are all more common in those with persistent pain. Patients with persistent pain have a reduced ability to carry out their social roles in their family or place of work. In addition, persistent pain often results in limited physical activity in patients, thereby worsening their physical conditioning.

BOX 27-1 IMPACT OF PERSISTENT PAIN

Depression

Sleep disturbance

Worsening physical conditioning

Loneliness

Loss of productivity

Financial loss

Loss of social support

Potential of drug abuse/misuse

It is estimated that the total cost of pain in the United States is between $560 and $635 billion in 2010 dollars. The cost to Medicare is believed to be approximately $65.3 billion, which is 14% of the Medicare budget. These figures do not include lost productivity or lost tax revenue. Disability from all causes costs the United States $300 billion annually, with the persistent pain–related causes of arthritis and back/spine pain being the top two causes of disability.⁴

Fourteen percent of the Medicare budget is consumed by pain treatment.

Pathophysiology

It is sometimes helpful from a clinical standpoint to classify persistent pain in pathophysiologic terms.² Nociceptive pain comes about from stimulation of peripheral pain receptors and may be from tissue or joint inflammation or degeneration, continuing injury, or skin or internal organ noxious stimulation. Inflammatory or degenerative arthritis, myofascial pain syndromes, or ischemia are examples of such pain. Pain with this etiology responds to usual analgesic medications and nonpharmacologic strategies. Neuropathic pain results from abnormal nerve stimulation that involves peripheral or cranial nerves. Examples include diabetic or idiopathic peripheral neuropathy, trigeminal neuralgia, or phantom pain. Pain of this etiology is often more difficult to treat and may not respond completely to any treatment. Medications used include certain antidepressants or anticonvulsants. Another category is pain of mixed or uncertain etiology. Examples include recurrent headaches, vasculitis, somatization, or conversion reactions. Treatment of this category is difficult and should be individualized for each patient.

There is a difference in pain perception and tolerance when comparing the elderly with younger people. Myelinated and unmyelinated nerve fibers are decreased in density in the elderly with prolonged latencies noted in peripheral sensory nerves. This slows transduction and transmission of the pain signals.⁵ There is a lower density of descending pain inhibiting nerve fibers in the elderly. In addition there is a slower recovery from hyperalgesic states⁶; once pain is established these changes may make it more likely that persistent pain develops after a noxious insult.

Most studies indicate that there is an increase in pain threshold with aging.² There is also an age-related decrease in the willingness to endure strong pain. From a clinical standpoint, such changes may be evident in the different pain presentations that the elderly have with either an acute myocardial infarction or a ruptured appendix.

Neuropathic pain refers to pain originating from abnormal peripheral or cranial nerve stimulation. Nociceptive pain refers to pain originating from stimulation of peripheral pain receptors.

CASE 1 Renee Peters (Part 1)

Renee Peters is a 78-year-old who comes to your office with increasingly severe low back pain. She has had low back pain for at least 5 years; the pain has intermittently interfered with her ability to do housework and leave her house. However, the pain worsened after she stepped down hard off a curb 1 week ago. There has been no radiation of pain to her buttocks or legs over the years.

1. What is the pathophysiology of Mrs. Peters’s pain?

2. How does the etiology of the pain influence therapy?

3. What do you expect to find on examination?

CASE 2 Bob Reid (Part 1)

Bob Reid is a 72-year-old who had an episode of shingles 4 months ago involving the right T7 dermatome. The rash cleared rapidly but severe pain persisted in the prior area of rash. He got only minimal relief with acetaminophen or ibuprofen. You had previously given him hydrocodone, which gave slightly more pain relief.

1. What is the pathophysiology of Mr. Reid’s pain?

2. How does the etiology of the pain influence therapy?

3. What do you expect to find on examination?

Pain assessment

Accurate assessment of pain is necessary to successfully treat it. This typically can include taking medical and pain histories, a physical examination with special attention to the painful areas, and using appropriate pain scales. Patients should routinely be evaluated for persistent pain (Level of Evidence B).

When taking a pain history, it is important that the clinician convey to the patient that his or her pain complaint is acknowledged and believed. It is also important that the patients know that pain is not a normal part of aging and they should not hesitate to discuss and describe their pain. Patients should be asked about a time line of the pain, acerbating and alleviating factors, and previous treatments. Descriptors of pain, such as sharp, burning, aching, radiating, or tightness should be sought (Level of Evidence D). Pain that awakens the patient from sleep may be particularly worrisome. How the pain affects the patient’s everyday life should be assessed. The physical examination should pay particular attention to the painful areas and how function of those areas is affected (Level of Evidence D). Areas of inflammation or tenderness should be sought. Weakness or limitation of motion, numbness, paraesthesia, or change in reflexes is important. Simply observing the patient’s gait can give information as to how the pain influences the patient’s activities of daily living. The “get up and go” test can help quantify the patient’s disability from the pain.

The patient must realize that his or her complaint of pain is taken seriously.

CASE 1 Renee Peters (Part 2)

On physical examination Mrs. Peters ambulates slowly with obvious pain. She has diffuse tenderness and spasm throughout the lumbar spine. There is more pronounced tenderness over the L3 spinous process. Her sensation and muscle strength of her lower extremities are normal. Her deep tendon reflexes are also normal. You suspect that Mrs. Peters has a lumbar compression fracture superimposed on degenerative disc disease and osteoarthritis involving the lumbar spine. This would be considered to be nociceptive pain with no evidence of significant neuropathic involvement. The severity of her pain should be evaluated. Most likely she will require opioid therapy for her acute fracture. Once the acute pain has improved, her persistent, ongoing low back pain will need further evaluation.

1. What further imaging or testing would you now recommend?

2. What other conditions relevant to Mrs. Peters should be addressed?

CASE 2 Bob Reid (Part 2)

On physical examination, Mr. Reid appears to be in pain and somewhat depressed. He has hyperalgesia involving the right T7 dermatome. There is no spine tenderness and his range of motion of the spine is normal. On further discussion with him, he admits that the constant nature of the pain has made him irritable and depressed.

1. What further imaging or testing would you now recommend?

2. What other conditions relevant to Mr. Reid should be addressed?

Pain quantitation

There are many tools to assess pain in the elderly, both the cognitively intact and the cognitively impaired.⁷ The most reliable way to evaluate the severity of pain of a cognitively intact patient is simply to ask the patient his or her estimate of the pain.² For those with mild to moderate dementia, reliable pain scales are available for use (Figure 27-1). Patients with advanced dementia are more difficult to evaluate, but clues from the patient’s behavior or actions may be helpful.⁸^,⁹ Grimacing, grunting, or constant movement may be clues to uncontrolled pain. The mental status of the patient often deteriorates with persistent pain.