Pain is categorized according to its duration, location and etiology. Three basic categories of pain are generally recognized: acute pain, chronic (persistent, nonmalignant) pain and cancer related pain. To further clarify pain terminology and treatment, many pain specialists now refer to chronic pain as persistent pain (pain that is not relieved by numerous intervention).
Regardless of its nature, pattern or cause, pain that is inadequately treated has harmful effects beyond the suffering it causes. For instance, unrelieved pain is associated with sleep alterations. Sleep deprivation affects the pain experience. Furthermore, sleep deprivation resulting from persistent pain produces hyperalgesic changes in which an individual reports an even greater pain sensation from the same stimulus when they are deprived of sleep and rest. Analgesics and other forms of pain relievers become less effective when individuals experience sleep deprivation.
Typically of recent onset and commonly associated with a specific injury, acute pain indicates that damage or injury has occurred. Pain is significant in that it draws attention to its existence and teaches people to avoid similar potentially painful situations. If no lasting damage and no systemic disease exist, acute pain usually decreases as healing spontaneously occurs.
For purposes of definition, acute pain can be described as lasting from seconds up to a maximum of 6 grueling months. However, the six month time frame has been criticized as rather inaccurate, because many acute injuries heal within a few weeks and most heal in 6 weeks. In a situation in which healing is expected in 3 weeks and an individual still continues to experience pain, the classification can be arguably be that of a persistent pain experience wherein appropriate treatment should be sought.
Chronic pain is a constant or intermittent pain that persists beyond the expected healing time that can seldom be attributed to a specific cause or injury. It may have a poorly defined onset or origin may be unclear. Although acute pain may be a useful signal that something is wrong, chronic or persistent pain usually becomes a problem in its own right.
Chronic pain may be defined as pain that lasts for 6 months or longer is an arbitrary period for differentiating between acute and chronic pain. An episode of pain may assume the characteristics of chronic pain before six months have elapsed, or some types of pain may remain primarily acute in nature for longer than 6 months. Nevertheless, after 6 months, most pain experiences are accompanied by problems related to the pain itself. Chronic pain serves no useful purpose, and if it continues it may become the individual’s primary disorder.
Effects of Acute and Chronic Pain
Unrelieved acute pain can affect the pulmonary, cardiovascular, gastrointestinal, endocrine and immune systems. The stress response
that occurs with trauma also occurs with other causes of severe pain. The widespread endocrine, immunologic and inflammatory changes that occur with stress can have significant negative effects. This is particularly harmful in individuals whose health is already compromised by age, existing illness or injury.
Like acute pain, chronic pain also has adverse effects. Suppression
of the immune function associated with chronic pain may promote tumor growth. Health care workers should understand the effects of chronic pain on patients and families and should be knowledgeable about pain relief strategies and appropriate resources to assist effectively with pain management.