6. 540 hospitalized cancer patients found that 85 percent of those with bone involvement had pain which required analgesic medication compared to only 5 percent of those with leukemia
7. 200 patients referred to a specialized cancer pain clinic, pain was caused by tumor growth in about 80 percent of cases.
21. Pathophysiology:noxious mechanical, thermal, or chemical stimuli which trigger nociceptors. Ischemia, inflammation, and perhaps substances produced by a nearby tumor may sensitize nociceptors to ordinarily nonnoxious stimuli.
24. Examples of primary and referred visceral pain in patients with cancer include the pain associated with pancreatic cancer, small bowel obstruction, and pleuritis
25. Mechanisms not well characterized, but visceral autonomic afferents may be involved
26.
27. Usually constant but may be interrupted by paroxysms of dramatically increased pain. There may be no area of tenderness, or areas of exquisite sensitivity to normally innocuous stimuli (allodynia).
30. Demyelinated axons may become sites of ectopic activity and aberrant (ephaptic) conduction of C or A-delta fiber impulses
31. NMDA receptors may be involved in perception and maintenance of neuropathic pain is suggested by the response to treatment with ketamine (also methadone).
45. Not clear if low-dose co-administration of ASA mitigates risk
46.
47. Predictably induce tolerance to and physical dependence on their effects. Despite the development of tolerance to opioid analgesia, disease progression is usually responsible for increasing analgesic requirements
48.
49. Initial agents: start with short half-life drugs (morphine, oxycodone, fentanyl, etc.). Once pain becomes constant transition to longer acting agents.
54. Both difficult to titrate as initial duration of action (4-6hrs) much shorter than t(1/2), may lead to accumulation during initial 2-5 days. Consider starting as PRN.
55. Methadone may be effective for neuropathic pain and prevention of tolerance due to NMDA antagonism in dorsal horn
56.
57.
58. Double-blind, randomized, crossover comparison of tramadol and morphine in 20 patients with severe cancer pain.Equivalent pain ratings were achieved with both drugs. Constipation and nausea were less severe and total side effects were fewer with tramadol.
61. Less likely to cause respiratory depression and constipation than equianalgesic doses of pure opioids, but does cause dizziness, nausea, dry mouth, and sedation.
67. Sigma receptor agonism ((pentazocine (Talwin) and butorphanol (Stadol)) may cause delirium
68.
69. After five or six half-lives(steady state plasma concentration), one day for morphine, the basal daily opioid requirement is determined and a long-acting opioid preparation is substituted (75% total requirment). This should be provided regularly to prevent most pain.
70. An additional short-acting opioid (5 to 15 percent of the basal daily requirement) is made available for breakthrough pain every 3-6 hrs.
71.
72.
73. Onset of analgesia 12-14hrs after application and continues 16-24hrs after removal. Some patients may require q48h (not q72h) reapplication
104. A Cochrane analysis of two randomized placebo-controlled trials concluded calcitonin provides no benefit to patients with metastatic bone pain.
105.
106.
107. Topical capsaicin has been useful for the treatment of mucocutaneous neuropathic pain, postmastectomy pain, PHN.
108. Studies have been complicated by difficulty in blinding because the active preparation causes a burning sensation.
109.
110. N/V: due to direct effect on chemoreceptor trigger zone, enhanced vestibular sensitivity, and slower gastric emptying. Tolerance develops quickly.
111. If nausea follows meals, use metoclopramide. If occurs with movement use meclizine.
MPQ: The patient chooses among 16 groups of descriptive words to characterize the sensory, affective, and evaluative qualities of his pain. Four additional word groups are specific to certain pain conditions. A pain intensity scale, a questionnaire on the use of analgesics and prior pain experience, and a human figure drawing on which the patient indicates his pain location are also included in the MPQ. The disadvantage of the MPQ is that it is not self-administered, and takes up to 20 minutes to complete. MPAC: designed to allow rapid assessment of cancer pain intensity, effectiveness of analgesics, and general psychological distress. It uses three visual analog scales and a set of eight pain intensity descriptors [27]. It may be self-administered and is more appropriate for cancer patients who are too fatigued or sedated to complete the MPQ. It appears to correlate with some of the more complicated instruments, yet it can be administered repeatedly without the evaluator's assistance.
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