'Pain is the most urgent of symptoms” H. K. Beecher. The word “pain” is derived from the Latin word “poena” meaning punishment. Pain is “an unpleasant sensory and emotional experience associated with tissue damage” (International Association for the Study of Pain). Pain and its treatment have occupied physicians and healers since the beginning of time. The consequences of pain include delayed healing, an altered immune system, and altered stress response. Managing pain and relieving suffering are at the core of a health care professional’s commitment to society.
Pain management begins with a careful assessment of the patient’s history, record review, physical exam, caregiver or family interview, and a look at available laboratory data and imaging studies. The treatment of pain should involve a multidimensional approach with consideration of invasive methods of pain control, while optimizing pharmacological and non-pharmacological approaches. Additional consults (e.g. pain specialists, radiation oncologists, neurosurgeons, neurologists, and mental health professionals) should also be considered if needed (1).
Four components of total pain includes physical, social, emotional, and spiritual. The assessment of pain by the patient may include the use of a numerical or visual analog scale which encourages patients to share information about a pain’s location, intensity, quality, and etiology. The numerical scale ranges from no pain 0 to maximum pain intensity of 10. Depending on the patients description of pain (sharp, dull, aching, stabbing, gnawing, cramping, burning, etc), these descriptions of pain will give the physician valuable clues as to the treatments which may help.
Pain syndromes of cancer may occur from different sources (2). Somatic/tissue and bone pain is caused by the activation of pain receptors infiltrated by tumor located in bone and muscle/soft tissue. Drug therapy may include opioid and anti-inflammatory drugs, steroids, or other adjuvants or radiotherapy for adequate relief. Visceral pain (pancreatic) is caused by the activation of pain receptors located within these organs. Pain is usually described as constant, aching, squeezing, or cramping. The pain is often poorly localized and may radiate away from the source. Drug therapy may include opioid and possibly anticholinergics. Pancreatic cancer may respond well to a nerve block procedure called celiac plexus block (named after the nerve plexus that surrounds the celiac artery and innervates the abdominal organs). Neuropathic pain involves the destruction, infiltration and/or compression of nerve tissue. This pain is described as constant or intermittent that may radiate. It may also be described as sharp and shooting. Drug treatment may include opioids, tricyclic antidepressants and possibly anticonvulsant medication.
Experts from the World Health Organization and Agency for Healthcare Research and Quality have recommended a three-tier strategy for pain management (3). Mild pain may respond to nonopioids (e.g., acetaminophen, nonsteroidal anti-inflammatory drugs [NSAIDS]). Mild to moderate pain may respond to the addition of a weak opioid such as hydrocodone or codeine in combination with acetaminophen or an NSAID. Moderate to severe pain should be treated with a strong opioid such as morphine, methadone, oxycodone, hydromorphone, and fentanyl. Care should be given to patients with hepatic and renal disease due to the way these medications are metabolized. Moderate to severe pain should be treated with scheduled dosing around the clock with extra doses made available for breakthrough pain. Care must be warranted because of well known side effects of opioids such as respiratory depression, constipation, urinary retention, myoclonus, delirium, and history of intolerable side effects.
Adjuvant analgesics are medications not typically used for pain relief but they may be effective for specific types of discomfort such as visceral, bone, and nerve pain. The World Health Organization recommends adjuvant medications be considered at all levels of pain severity. Primary among these drugs are traditional antidepressants and anticonvulsants.
Selective invasive methods of pain relief include nerve blocks, spinal infusions, surgery, and radiation therapy (4). Nerve blocks may include peripheral nerve, celiac plexus or hypogastric plexus nerve block. The control of intractable pain can be achieved with a brief application of a local anesthetic or neurolytic (alcohol or phenol). Nerve blocks can be performed for several reasons including 1. Diagnostic: the determination of the source of pain, 2. Therapeutic: to treat painful conditions that respond to nerve blocks (e.g., celiac plexus block for pancreatic cancer), 3. Prognostic: to predict the outcome of long lasting interventions (e.g., infusions, neurolysis), and 4. Preemptive: to prevent painful sequelae of procedures that may cause phantom limb pain or other painful conditions.
Spinal infusions involves the placement of a small catheter into the epidural or intrathecal space of the spine to provide the continuous infusion of a single agent or the combination of several medicines such as opioids, local anesthetics, and clonidine. Much smaller doses are usually required and side effects may be minimal. If effective, a more permanent catheter can be tunneled subcutaneously for outpatient use.
Radiation therapy involves the local or whole body radiation to enhance the effectiveness of analgesic drug therapy by directly affecting the cause of pain (i.e., reducing the primary and metastatic tumor bulk). A dosage is chosen to achieve a balance between the amount of radiation required to kill tumor cells and that which adversely effects normal cells. Radiation therapy also includes the use of an intravenous injection of beta particle emitting agents such as iodine-131 or strontium-89.
Surgery may involve curative or palliative debulking of a tumor that may reduce pain directly, relieve symptoms of obstruction or compression, and improve prognosis. The potential benefits and burdens of surgery (including pain syndromes that follow specific surgical procedures) should be carefully considered in light of the patients goals of care and expected prognosis. Neurosurgical procedures may block pain pathways with devices that can be implanted to deliver drugs or to electrically stimulate neural structures. Generally, the choice of neurosurgical procedure is based upon the location and type of pain, the patients general condition and life expectancy, and the available expertise and follow-up.
References
1. Cancer Pain: Assessment and Management. ED Bruera and RK Portenoy, eds. Cambridge University Press, New York, NY. 2003
2. Pereira J, Bruera E. The Edmonton Aid to Palliative Care. Edmonton, Alberta, Canada: Division of Palliative Care, University of Alberta; 1997
3. Cancer Pain Relief (2nd Edition). World Health Organization. Geneva, 1996: 15
4. Jacox A, Carr DB, Payne R et al. Management of Cancer Pain. AHCPR Publication No. 94-0593. Rockville, MD. Agency for Health Care Policy and Research, U.S. Department of Health and Human Services. Public Health Service, March 1994:18-19
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