Pain is an unpleasant sensory and psychological experience that normally accompanies actual or potential damage to the body’s tissues. Pain alerts the body to dangerous situations or injuries. Doctors use the term acute pain to describe pain that occurs suddenly and fades within hours, days, or weeks after correcting the underlying cause. Acute pain helps in survival because the body generally reacts to pain by trying to avoid the harmful circumstances that cause it. For example, pain causes people to automatically pull their hands away from a hot object, helping them avoid burns.
Pain that lasts more than a few months is called chronic pain. Such pain may begin with an injury, such as a sprain, or may result from an ongoing condition, such as arthritis, cancer, or diabetes. However, some people suffer chronic pain without any injury or evidence of damage to the body. With chronic pain, the nervous system may undergo changes that can cause the pain to continue despite the absence of a painful stimulus (triggering event or condition). Chronic pain interferes with sleep and can lead to depression.
Many long-term diseases that cause chronic pain become more common as people age. The number of people living with chronic pain has thus grown as human life span has increased. Today, many physicians specialize in pain medicine—the evaluation, treatment, and management of chronic pain.
How the body feels pain.
Pain begins in specialized nerves called nociceptors, which convert a hurtful stimulus into electrical energy. This energy triggers a pain signal that passes through a sequence of nerve structures called a pain pathway. The signal travels along pain nerves to the spinal cord and finally, to the brain. When the signal reaches the brain, the person becomes aware of pain. The brain, however, can release chemicals that inhibit (halt) pain signals.
Several different conditions can cause the body to feel chronic pain. Repeated painful experiences can cause central sensitization, an increase in the sensitivity of nerves within the central nervous system. With the increase in sensitivity, normal stimuli can produce an abnormal pain response, resulting in chronic pain. Nerve injury can cause peripheral nerve pain, an increase in sensitivity of the nociceptors. Other causes of chronic pain affect the sympathetic nervous system, a part of the nervous system that responds to the body’s needs during increased activity and in emergencies. If these conditions are not treated, they can result in lifelong pain.
Psychological factors, such as excitement or fear, can also influence the experience of pain. For example, athletes who are extremely excited about a game may be injured without feeling pain and continue to play. In contrast, a patient’s anticipation and fear can increase the pain of a medical procedure.
Treatment.
In treating acute pain, doctors aim to remove the painful stimulus and alleviate the pain response. For example, doctors treat a broken leg by setting the bone and giving drugs called analgesics until the pain of the break subsides. Commonly prescribed analgesics include acetaminophen and a group of drugs called nonsteroidal anti-inflammatory drugs, often abbreviated NSAID’s. Aspirin and ibuprofen are the most familiar NSAID’s. For extreme acute pain—for example, pain resulting from a surgery—physicians may prescribe opioids , such as morphine or oxycodone.
Treating chronic pain is usually more complex and often combines the use of drugs with other therapies. Doctors may inject an anesthetic (sensation-deadening drug) directly around a nerve to interrupt the transmission of pain signals to the brain. A treatment plan may also involve physical therapy, exercise, yoga, acupuncture, and massage. Cognitive behavioral therapy teaches people to use their thoughts to help control pain. Relaxation techniques and hypnosis may also help.
