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Pain is a protective mechanism of the body and is the perception of tissue injury. It consists of sensory and emotional aspects. The sensory aspect is due to nerve endings in the damaged tissue transmitting the pain impulse to the central nervous system and the brain, resulting in the perception of pain. The patient reacts to pain in an emotional way, resulting in pain being inherently subjective. About 90% of cancer patients experience pain during the course of the disease, and many studies have shown that pain is frequently under treated.
Before the physician can adequately treat pain, he must assess the nature of the pain. A simple rating scale, such as 0-10, can very adequately describe the intensity of pain, with zero being "no pain," and 10 being "pain as severe as you can imagine." The characteristics of the pain are important in order to determine the cause. The patient should describe the pain, where the pain seems to be coming from, if the pain radiates from one area to another, and how the pain varies at certain times of the day or after certain activities. Causes of cancer pain 2 Persistent pain due to stimulation of nerve endings can be due to tumor invasion of bone, joint, muscle or connective tissue. Since many cancers are attracted to bone, early diagnosis and treatment of tumors that have invaded the vertebral column can minimize neurological damage to the spine and nerve endings. Tumor infiltration or compression of the nerves or nerve network can cause pain. Treatment-related pain is primarily due to nerve injury, and can be caused by surgical cutting of nerves, radiation induced fibrosis of tissues, and chemotherapy that is toxic to nerves. Pharmacological treatment of pain The mainstays for the treatment of pain are the opioids. This term derives from the opium plant, which is the source of morphine, a natural painkiller. Opium also contains codeine, while researchers have developed many synthetic opioids, including oxycodone, hydromorphone, hydrocodone, tramadol, oxymorphone, methadone, and fentanyl. All these opioids act by binding to receptors located in the brain and spinal cord. Since these receptors are involved in the transmission and modulation of pain, opioid binding blocks transmission and alleviates pain. Physicians tend to follow guidelines established by the World Health Organization 3 for the treatment of pain. These guidelines are organized into three "steps," which are designed to treat the pain by using drugs that have the least side effects to achieve the desired result. Accordingly, physicians treat mild pain with non-steroidal anti-inflammatory drugs, such as aspirin, ibuprofen, and naproxen, as well as acetaminophen. Moderate pain is treated with weaker opioids such as codeine, or stronger opioids in lower doses or in combination with non-opioids. Finally, severe pain is treated with full doses of opioids such as morphine, oxycodone, hydromorphone or fentanyl. Other strategies 1 include switching opioids to maintain patient response, and the use of adjuvant (co-administered) drugs to reduce the dosage of opioids. |
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