Eric G. Bush and Anne Berger
DEFINITIONS
■Palliative care is based on a holistic model of symptom management. It concerns improving the quality of life (including end-of-life care) for patients and their families facing life-threatening illnesses by preventing, identifying, and relieving suffering associated with physical, psychosocial, and spiritual problems. For cancer patients, pain is the most common reason for palliative care consultation.
■Acute pain is the predictable physiologic response to an adverse chemical, thermal, or mechanical stimulus. It is normally associated with surgery, trauma, and acute illness. It is generally time limited and responsive to a variety of pharmacologic and nonpharmacologic therapies.
■When acute pain persists over time, it is classified as chronic pain.
■Pain is usually, but not always, associated with tissue damage. It is always subjective and may be influenced by emotional, psychological, social, and spiritual factors, as well as financial concerns and fear of death.
■Neuropathic (stimulus-independent) pain is characterized by dysesthesia, allodynia, or hyperalgesia. It may be secondary to direct tumor involvement or may be treatment related after surgery, radiation, or chemotherapy. Agents associated with chemotherapy-related neuropathic pain include vincristine, cisplatin, procarbazine, and thalidomide (or thalidomide analogs). Neuropathic pain may be treated effectively with antidepressants or anticonvulsants.
EPIDEMIOLOGY
■Most cancer patients experience some degree of pain, especially in the advanced and metastatic phases of disease. In advanced cancer, the prevalence of pain is about 70%, but varies with the type and stage of disease.
■There are several published guidelines for cancer pain management recommended by the World Health Organization (WHO), and effective treatments are available for 70% to 90% of cases.
■Nevertheless, an estimated 40% of cancer patients remain undertreated for reasons related to the health care provider, the patient and family, or cultural mores. The most frequent cause of under treatment is misconceptions about the use of opioids.
ASSESSMENT
■Proper pain assessment can help to establish a good doctor/patient relationship, guide the therapeutic regimen, improve pain management, maximize patient comfort and function, and increase patient satisfaction with therapy. Failure to fully assess pain in the cancer patient may result in adverse pain outcomes, regardless of the amount or type of analgesia and adjuvants used.
■Patients’ self-reports should be the main source of pain assessment. For infants and the cognitively impaired, physicians can utilize nonverbal pain scales (PAIN-AD, Wong-Baker Faces, CNVI).
■For rapid assessment of acute pain, select a simple measurement of pain intensity (Fig. 40.1) and record the measurement for treatment evaluation.
■Patients should be reassessed frequently by inquiring how much their pain has been relieved after each treatment. A consistent disparity between patient’s self-report of pain and their ability to function necessitates further assessment to ascertain the reason for the disparity.
■Underlying anxiety and depression can increase patient suffering. Inadequate assessment of these factors may result in under- or overtreatment with analgesics.
FIGURE 40.1 Common tools for assessment of pain intensity. (Adapted from the American Geriatrics Society [AGS] Panel on Chronic Pain in Older Persons. The management of chronic pain in older persons. J Am Geriat Soc. 1998;46:635-651; Gloth FM III, Scheve AA, Stober CV, et al. The functional pain scale (FPS): reliability, validity, and responsiveness in a senior population. J Am Med Direct Assoc. 2001;3:110-114; and Gloth FM III. Assessment. Handbook of Pain Relief in Older Adults: An Evidence-Based Approach. Totowa, NJ: Humana Press; 2003:17.)
TREATMENT
■Severe pain should be considered a medical emergency; timely and aggressive management should be provided until the pain becomes tolerable. Aggressive pain management, with the goal of attaining maximal functional ability, is especially important with cancer patients.
■Sedatives and anxiolytics alone should not be used to manage pain as they can mask the behavioral response to pain without providing analgesia.
■NSAIDs or acetaminophen should be used to manage mild to moderate pain, unless contraindicated.
■Opiates are the foundation of management for severe pain.
■For cancer-related anxiety and depression, treatment approaches include tricyclic antidepressants, SNRIs, SSRIs, spiritual, and psychosocial intervention.
OPIATES
■Opiate therapy should be tailored to each patient, based on the type and expected duration of pain, as it is difficult to predict which patients will achieve adequate analgesia or develop intolerable adverse effects from a given opiate.
■Tolerance and physical dependence are expected with long-term opiate treatment and should not be confused with psychologic dependence (addiction).
■Equianalgesic doses of oral opiates (Table 40.1) should be prescribed when necessary.
■Begin administration of opiates at lowest effective dose and titrate as necessary. No maximal therapeutic dose for analgesia has been established.
■Immediate-release opiates (mu receptor agonists) are short-acting and may be appropriate for acute incidental pain, or to initiate and titrate opiate therapy. Long-acting opiates are used around the clock for baseline pain and to maintain analgesia.
■Methadone can be an excellent agent for management of pain, but utilization or consideration should prompt referral to a pain specialist.
■Titration of opiates: Start at lower doses and titrate as tolerance to side effects develops. If pain persists titration upward by dose increments of 30% to 50% may be necessary to achieve adequate analgesia. For severe uncontrolled pain (extremis), increase the dose by up to 100% and reassess at peak effect.
■Early side effects often improve or resolve with repeated doses. With the exception of constipation, tolerance often develops rapidly to most of the common opiate-related adverse effects.
■Common adverse effects of opiates include constipation, sedation, nausea/vomiting, pruritus, sweating, dry mouth, and weakness.
■Uncommon adverse effects of opiates include dyspnea, urinary retention, confusion, hallucinations, nightmares, myoclonus, dizziness, dysphoria, and hypersensitivity/anaphylaxis.
Long-Term Opiate Use
■Physicians have an ethical and regulatory duty to inform the patient of the risks and benefits of long-term opiate use, particularly when initiating treatment in patients at high risk for misuse of opiates (utilize random urine drug tests, referrals to pain management physicians and pain contracts in high-risk patients).
■Certain factors, such as personal or family history of substance abuse, risk of diversion of opiates, or lack of compliance, dictate a multidisciplinary approach, including the involvement of a pain specialist.
■Long-term use of opiates should always be supported by maximal use of coanalgesics and adjuvants, psychological therapy, and appropriate follow-up.
Risks of Long-Term Opiate Use
■Addiction: Extremely rare in cancer patients
■Physical dependence: Manifested by withdrawal syndrome at cessation or dose reduction
■Tolerance: Diminution of one or more of the opiate’s effects over time
■Pseudoaddiction: Iatrogenic syndrome that develops in response to inadequate pain management
Termination of Opiate Therapy
■When opiates are no longer required for pain management, appropriate tapering is essential to reduce the risk of withdrawal syndromes. The recommended regimen involves reducing dosage by 10% to 20% daily, or more slowly if symptoms such as anxiety, tachycardia, sweating, or other autonomic symptoms arise.
■Symptoms may be relieved by clonidine 0.1 to 0.2 mg per day PO or low-dose transdermal patch every third day.
ADJUVANT ANALGESICS
■An adjuvant analgesic is any drug with a primary indication other than pain, but with proven analgesic effect in specific circumstances.
■Indications include poor response to opiate, opiate toxicity, or pain that is more responsive to adjuvant (i.e., neuropathic, bone, visceral, or myofascial pain).
■Adjuvants should be tried one at a time until analgesia is achieved or side effects become intolerable. If only partial analgesia is reached at maximal dose of one adjuvant, consider adding a second adjuvant.
■Potential benefits of adjuvant analgesia include targeting of multiple pain pathways, complementary pharmacodynamic activity, potentially synergistic analgesic effects, and reduced adverse events with comparable efficacy.
NONPHARMACOLOGIC THERAPY
■Psychologic and behavioral interventions may enhance the benefits of pain medications or help to reduce their use.
■Integration of these modalities into treatment should be culturally sensitive and tailored to patients’ individual needs.
■Modalities include, among others, acupuncture, relaxation/biofeedback, recreation/art/music therapy, reiki/healing touch, transcutaneous electrical nerve stimulation (TENS), myofascial trigger release, and behavioral counseling.
REVIEW QUESTIONS
1.A 58-year-old male with a history of metastatic renal cell carcinoma is admitted to the oncology service for worsening pain. His pain previously had been well controlled with twice daily use of hydrocodone 5 mg/acetaminophen 500 mg tablets. His primary focal pain complaint includes left hip pain confirmed by radiography to be osseous metastatic disease. The patient rates his pain as 8/10 on a visual analog scale (VAS) and assessment confirms a clearly uncomfortable gentleman of stated age. Which of the following would be an appropriate initial parenteral analgesic to better control his pain?
A.Propoxyphene
B.Meperidine
C.Hydromorphone
D.Oxycodone
E.Ibuprofen
2.The patient in question 1 now has improved pain control after choosing an appropriate analgesic. The patient is utilizing a total of 100 mg of oral morphine equivalents and has improved pain and functionality with a pain rating of 3/10 on a VAS. Which of the following would be an appropriate long-acting opiate to initiate at this time?
A.Methadone tablets 30 mg PO TID
B.Oxycodone extended release tablets 80 mg PO TID
C.Morphine sulfate extended release tablets 100 mg PO TID
D.Oxycodone immediate release tablets 30 mg PO q4h
E.Fentanyl transdermal patch 25 mcg topically q72h
3.The patient in questions 1 and 2 continues to have good pain relief (VAS 3/10) after receiving appropriate long and short-acting opiate analgesics. He continues to utilize short-acting analgesics twice daily. In total this utilization equivocates to 30 mg of oral morphine equivalents. He is now ready for discharge home, which of the following would be an appropriate regimen for breakthrough pain that the patient could receive at home?
A.Hydromorphone 8 mg tablets BID prn pain
B.Morphine sulfate immediate release 30 mg tablets BID prn pain
C.Oxycodone immediate release tablets 30 mg BID prn pain
D.Hydromorphone 4 mg tablets BID prn pain
E.Fentanyl transdermal patch 25 mcg topically q72h
Suggested Readings
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