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Pain
FREQUENCY
The frequency of pain among terminally ill patients varies widely. The proportion of
advanced cancer patients experiencing substantial pain is reported to range from 36 to
90%. In the SUPPORT study of hospitalized patients with diverse conditions and an
estimated survival of ≤6 months, 22% reported moderate to severe pain, and
caregivers of these patients reported that 50% had similar levels of pain during the last
few days of life.
Constipation Delirium
Cough
Swelling of arms or legs
Itching
Diarrhea
Dysphagia
Dizziness
Loss of libido
Fecal and urinary incontinence
Numbness/tingling in hands/feet
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ETIOLOGY
Nociceptive pain is the result of direct mechanical or chemical stimulation of
nociceptors and normal neural signaling to the brain. It tends to be localized, aching,
throbbing, and cramping. The classic example is bone metastases. Visceral pain is
caused by nociceptors in gastrointestinal, respiratory, and other organ systems. It is a
deep or colicky type of pain classically associated with pancreatitis, myocardial
infarction, or tumor invasion of viscera. Neuropathic pain arises from disordered,
ectopic nerve signals. It is burning or shocklike pain. Classic cases are post-stroke pain
and tumor invasion of the brachial plexus. Well-recognized pain syndromes are
associated with peripheral neuropathy after chemotherapy or surgery.
ASSESSMENT
Pain is a subjective experience. Depending upon the patient's circumstances,
perspective, and physiologic condition, the same insult can produce different levels of
reported pain and need for pain relief. Systematic assessment includes eliciting the
following: (1) periodicity—continuous, with or without exacerbations, or incident; (2)
location; (3) intensity; (4) modifying factors; (5) effects of treatments; (6) functional
impact; and (7) impact on patient. Several validated pain assessment measures may be
used, such as the Visual Analogue Scale, the Brief Pain Inventory, and the pain
component of the Memorial Symptom Assessment Scale. Frequent reassessments are
essential to assess the effects of interventions.
INTERVENTIONS
Interventions for pain must be tailored to each individual with the goal of preempting
chronic pain and relieving breakthrough pain. At the end of life, there is no reason to
doubt the patient's report of pain. Pain medications are the cornerstone of
management. If these are failing and nonpharmacologic interventions—including
radiotherapy, anesthetic or neurosurgical procedures, such as peripheral nerve blocks
or epidural morphine—are required, a pain consultation is appropriate.
P harmacologic interventions follow the World Health Organization
three-step approach involving nonopioid analgesics, mild opioids, and strong opioids,
with or without adjuvants (Chap. 11). Nonopioid analgesics, especially nonsteroidal
anti-inflammatory drugs, are the initial treatments for mild pain. They work primarily by
inhibiting peripheral prostaglandins, reducing inflammation, but may also have central
nervous system (CNS) effects. They have a ceiling effect. Ibuprofen, up to 1600 mg/d,
has a minimal risk of bleeding and renal impairment and is a good initial choice.
If nonopioid analgesics are insufficient, then opioids should be introduced. They work
by interacting with mu opioid receptors in the CNS to activate pain-inhibitory neurons;
most are receptor antagonists. The mixed agonist/antagonist opioids useful for postacute
pain should not be used for the chronic pain in end-of-life care. Weak opioids,
such as codeine, should be used initially. However, if the weak opioids are escalated
and also fail to relieve pain sufficiently, then strong opioids, such as morphine 5 to 10
mg every 4 h, should be used. Nonopioid analgesics should be combined with opioids
because they potentiate the effect of opioids.
For continuous pain, the opioids should be administered on a regular, around-the-clock
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basis consistent with their duration of analgesia. They should not be provided only
when the patient experiences pain; the goal is to prevent patients from experiencing
pain. Patients should also be provided rescue medication, such as liquid morphine, for
breakthrough pain and should be instructed to take one-half of the standing opioid
dose. Patients should be informed that using the rescue medication does not obviate
their taking the next standard dose of pain medication. If after 24 h the patient's pain
remains uncontrolled and recurs before the next dose, requiring the patient to utilize
the rescue medication, increase the daily opioid dose by the total dose of rescue
medications used by the patient, or by 50% for moderate pain and 100% for severe pain
of the standing opioid daily dose.
It is inappropriate to start with extended-release preparations. Once pain relief is
obtained, then switch to extended-release preparations. Even with a stable extendedrelease
preparation regimen, the patient may have incident pain, such as pain during
dressing changes. Short-acting preparations should be used to cover such predictable
episodes.
Because of differences in opioid receptors, cross-tolerance among opioids is
incomplete and patients may experience different side effects with different opioids.
Therefore, if a patient is not experiencing pain relief or is experiencing too many side
effects, change to another opioid preparation. When switching, begin with ≥50% of the
published equianalgesic dose of the new opioid. (Starting at 25% of the equianalgesic
dose is inadequate for terminally ill patients.) Opioids have no ceiling effect; therefore,
there is no maximum dose no matter how many milligrams the patient is receiving. The
appropriate dose is the dose needed to achieve pain relief. Addiction or excessive
respiratory depression is extremely unlikely in the terminally ill; fear of these side
effects should neither prevent escalating opioid medications when the patient is
experiencing insufficient pain relief nor justify using opioid antagonists, such as
naloxone.
Opioid side effects should be anticipated and treated preemptively. Nearly all patients
experience constipation that can be quite debilitating (see below). Failure to prevent
constipation often results in noncompliance with narcotic therapy. About a third of
patients experience nausea and vomiting, but tolerance develops, usually within a
week. Therefore, when beginning opioids, an antiemetic, such as metoclopramide or a
serotonin antagonist, should be prescribed prophylactically and stopped after 1 week.
Drowsiness, a common side effect of opioids, also abates within a week. During this
period, drowsiness can be treated with psychostimulants, such as dextroamphetamine
or methylphenidate. Anecdotal reports suggest that donepezil may also be helpful for
opiate-induced drowsiness. Metabolites of morphine and most opioids are cleared
renally; doses may need to be adjusted for renal failure.
Patients and families may withhold the prescribed opioids for fear of addiction or
dependence. Physicians and health care providers must reassure patients and families
that the patient will not become addicted or dependent upon the opioids if used as
prescribed for pain relief; this fear should not prevent the patient from taking the
medications around the clock.
Seriously ill patients with chronic pain relief rarely if ever become addicted. Suspicion
of addiction should not be a reason to withhold pain medications from terminally ill
patients. However, diversion of drugs for use by other family members or illicit sale may
occur. If this occurs, it should be managed in a way that does not inflict unnecessary
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pain on the dying patient. Contract writing with the patient and family can help. If that
fails, transfer to a safe facility may be necessary.
Tolerance is the need for increasing medication dosage for the same pain relief without
a change in disease. In the case of patients with advanced disease, the need for
increasing opioid dosage for pain relief is usually caused by disease progression rather
than tolerance. Physical dependence is indicated by symptoms from the abrupt
withdrawal of opioids and should not be confused with addiction.
Adjuvant analgesic medications are nonopioids that potentiate the analgesic effects of
opioids. In the management of neuropathic pain, tricyclic antidepressants, such as
desipramine, which has fewer side effects than other tricyclic antidepressants, can
begin to work in a few days at doses of 10 to 25 mg before bedtime. Similarly,
anticonvulsants, especially gabapentin (begun at 100 mg tid and titrated up by 100 mg
tid until relief, with usual doses between 300 mg and 1200 mg tid) or carbamazepine,
have shown effectiveness in relief of neuropathic pain. Glucocorticoids, preferably
dexamethasone provided once a day, can be useful in reducing inflammation that
causes pain while elevating mood, energy, and appetite. Other drugs, including
clonidine and baclofen, can be effective in pain relief. These drugs are adjuvants and
should all be used in conjunction with—not instead of—opioids. Methadone, carefully
dosed, has activity at the N-methyl D-aspartamate (NMDA) receptor and is useful for
complex pain syndromes and neuropathic pain.
Radiation therapy can treat bone pain from single metastatic lesions. Bone pain from
multiple metastases can be amenable to radiopharmaceuticals, such as strontium 89
and samarium 153. Pamidronate (90 mg every 4 weeks) and calcitonin (200 IU
intranasally once or twice a day) can also provide relief from bone pain. |
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